bluuebunny/crossref_metadata_2025 huggingface dataset:
Microfluorimetric quantitation of cellulose biosynthesis by plant protoplasts using Calcofluor White
Authors: Galbraith David W.
Published: April 2006

A microfluorimetric procedure, using Calcofluor White, has been developed for the measurement of cellulose biosynthesis by cultured protoplasts of tobacco (Nicotiana tabacum L. cv. Xanthi nc). The procedure was compared to a conventional method for cellulose estimation, that employing the anthrone reagent following exhaustive extraction of the developing cell walls. The results indicate that the amount of fluorescence emitted following Calcofluor White treatment is a specific measurement of cell wall cellulose levels. The procedure possesses the twin advantages of ease of manipulation and of greatly enhanced sensitivity (in the picogram range) as compared to other methods.
Quantum yield and energy dependence for photooxidation of chlorophyllide in greening wheat
Authors: Axelsson Lennart
Published: April 2006

Dark grown leaves of wheat were irradiated with red light of different intensities, at a temperature close to 0°C. The rate of photoreduction of the protochlorophyllide 650‐form into chlorophyllide 684‐form was measured. On continued irradiation the chlorophyllide 684‐form was photodecomposed. By comparing the rates of the two processes the quantum yield for photooxidation of the chlorophyllide 684‐form was calculated. The quantum yield was 2°10‐5 at an intensity of 2200 W m‐2, and increased with decreasing light intensity to 3.2°10‐5 at an intensity of 170 W m‐2.
ATP‐levels of germinating seeds in relation to vigor
Authors: Lunn Gorm , Madsen Erik
Published: April 2006

Determination of seed vigor was attempted by comparing ATP‐levels of deteriorating seed to germination percentage and production of dry matter. Immediately after imbibition of any seed lot investigated, a production of ATP took place. This ATP‐accumulation invariably reached a plateau after 6 h of imbibition. Two well germinating seed lots of rape, one of cauliflower and one of sugar beet, were artificially aged by means of elevated storage temperature and humidity. Every second week through 16 weeks of deterioration the levels of ATP, ADP and AMP after 7 h of imbibition were compared with the germination percentage. While ADP‐ and AMP‐contents of germinating seed displayed no change (when imbibed 7 h) during the period of artificial aging, seed deterioration was reflected in the ATP‐levels long before loss of viability could be detected by the conventional germination test.

When ATP‐levels per seed were related to germination percentage throughout the aging, all four seed lots displayed similar patterns although the absolute figures differed. In contrast to the conventional “per seed’ basis, however, ATP per gram seed not only displayed similar deterioration patterns, but the absolute values were also of the same magnitude.
Energy metabolism of Plantago major ssp. major as dependent on the supply of mineral nutrients
Authors: Lambers Hans , Posthumus Freek , Stulen Ineke , Lanting Lineke , van de Dijk Siebren J. , Hofstra Rinie
Published: April 2006

Plantago major L. ssp. major, a grassland species from a relatively nutrient‐rich habitat, was grown in nutrient‐rich and nutrient‐poor culture solutions. Half of the plants were transferred from high to low or from low to high nutrient conditions. The rate of dry matter accumulation in both shoots and roots decreased slowly upon transfer of plants to low nutrient conditions and the shoot to root ratio was unaffected. The rate of structural growth of both roots and shoots increased upon transfer from low to high nutrient conditions and the shoot to root ratio, if calculated from non‐structural‐carbohydrate‐free dry weights, increased.

Photosynthesis was largely independent of the nutrient supply. Root respiration, particularly the activity of the alternative oxidative pathway, decreased with increasing age. This decrease was ascribed to a decreased shoot to root ratio, which reduced the relative amount of carbohydrates translocated to the roots and thus the amount available for the alternative pathway. It is calculated that in young as well as in old plants grown in full nutrient solution 48% of the daily produced photosynthates was translocated to the roots.

This is at variance with data on P. lanceolata, where a decreasing proportion of the daily produced photosynthates was translocated to the roots when the plants grew older. It is concluded that shoot growth plus shoot respiration consumed a constant amount of the daily produced photosynthates in P. major and that the rest was left for translocation. It is further calculated that in P. major plants grown in full nutrient solution c. 25% and c. 2% of the daily produced photosynthates in young and old plants, respectively, was respired in a way that is not involved in production of energy that is utilized in growth and maintenance (‘inefficient root respiration’).

The results are discussed in comparison with those of P. lanceolata, a species from a relatively nutrient‐poor habitat.
Fractionation of the proteinases present in the endosperm of germinating seed of Scots pine, Pinus sylvestris
Authors: Salmia M. Aulikki
Published: April 2006

When fresh extracts of endosperms separated from germinating seeds of Scots pine were dialysed at 5°C, proteinase activity on haemoglobin at pH 3.7 showed only a small initial increase, proteinase activities on casein at pH 5.4 and at pH 7.0 increased several‐fold, and all the corresponding inhibitor activities disappeared (Salmia and Mikola 1980, Physiol. Plant. 48: 126–130). To find out what happens during dialysis, both fresh and dialysed extracts were fractionated by gel chromatography on Sephacryl S‐200. – The fresh extracts had a major proteinase peak (mol. wt. 42,000) with high activity at pH 3.7 and moderate activities at pH 5.4 and 7.0 (pine proteinase I) and a smaller peak (mol. wt. 30,000) with high activity at pH 5.4 and 7.0 and smaller activity at pH 3.7 (pine proteinase II). In dialysed extracts the situation was reversed: the peak of proteinase I was very small while the peak of proteinase II was very high. Apparently, proteinase I is largely inactivated during dialysis while the activity of proteinase II increases, at least partly due to destruction of inhibitors. – The two enzymes were ‐SH proteinases, as they were completely inhibited by p‐hydroxymercuribenzoate; both of them were also inhibited by the endogenous proteinase inhibitors of resting pine seeds. Besides these enzymes, the endosperm extracts contained pepsin‐like acid proteinase activity, which is not affected by the endogenous inhibitors. This enzyme activity was largely inactivated during dialysis.
The influence of spectral quality on the internodal response of intact bean plants to brassins
Authors: Krizek Donald T. , Worley Joseph F.
Published: April 2006

The response of pinto bean (Phaseolus vulgaris L.) plants to single application of brassins (10 μg) in the second‐internode assay was determined under equal levels (90 μE m−2 s−1) of photosynthetically active radiation in a controlled environment provided by cool‐white fluorescent (CWF) lamps, incandescent (INC) lamps, or a combination of the two sources. Treatment of the second internode with brassins produced a characteristic swelling of the treated internode irrespective of the spectral source used. However, the increase in radial growth of the upper portion of brassin‐treated internodes from plants grown under INC lamps was more than 50% greater than those of plants grown under CWF lamps for 7 days. Spectral quality also had a marked effect on the rate and extent of internode elongation. Brassin‐treated internodes of plants grown for 7 days under CWF lamps were more than twice as long as those of control plants, whereas those from INC or CWF + INC grown plants were significantly shorter than those of control plants. The effect of brassins was largely confined to the treated internode.
Stomatal behaviour and cuticular properties of maize leaves of different chilling‐resistance during cold treatment
Authors: Vigh László , Horváth Ibolya , Farkas Tibor , Mustárdy László A. , Faludi‐Dániel Ágnes
Published: April 2006

Stomatal behaviour and the amount and synthesis of epicuticular waxes were studied in maize leaves of various degrees of chilling resistance in order to investigate the rapid desiccation characteristic of chilling injury. In contrast to the resistant variety (KSC 360), the sensitive line (Lye) failed to close the stomata during chilling treatment. Both, the amount of epicuticular waxes and their degree of labeling by 1‐14C‐acetate were much higher in the resistant than in the sensitive leaves. Chilling‐sensitivity was also related to a suppressed conversion of free fatty acids into free primary alcohols.
The effect of nitrogen on plant water relations in tea (Camellia sinensis)
Authors: Nagarajah S.
Published: April 2006

An experiment was carried out to study the effect of nitrogen deficiency on the water relations of tea (Camellia sinensis). The plants were grown in sand and nitrogen deficiency induced by witholding the supply of nitrogen. Nitrogen deficiency increased stomatal resistance and reduced transpiration. The capacity of the stomata to open fully in the morning was not impaired by nitrogen deficiency. Leaf water potential and probably root resistance were not affected by nitrogen deficiency. The sensitivity of transpiration and stomatal resistance to sand water stress was increased by nitrogen deficiency.
Anatomical and physiological characteristics of the petiole of Abutilon theophrasti in relation to circadian leaf movements
Authors: Fuhrman Margaret H. , Koukkari Willard L.
Published: April 2006

Leaf movements in Abutilon theophrasti Medic, were monitored manually and by a continuous electronic recording device. Plants entrained to a daily regime of a 15 h light span followed by 9 h of darkness showed rhythmic movements that persisted under conditions of continuous illumination and constant temperature with a circadian period. The rhythmic change in orientation of the leaf from a near horizontal (day) to a near vertical (night) position was attributed to movement of the blade and not the petiole. The end of the petiole next to the blade functions as a joint or pulvinus. Anatomical confirmation of the existence of a pulvinus in the Abutilon leaf was provided by light microscopy. Vascular tissue in this region forms a solid cylinder with no pith, and the cortex is parenchymatous. In the main part of the petiole, the vascular tissue is arranged in four to six bundles, a pith is present, and the cortex contains a sub‐epidermal ring of collenchyma. Both the functional and anatomical evidence indicate the presence of a pulvinus that functions in circadian leaf movements of Abutilon.
Enzymes of the tricarboxylic acid cycle and the malate‐aspartate shuttle in the N2‐fixing endophyte of Alnus glutinosa
Authors: Akkermans Antoon D. L. , Huss‐Danell Kerstin , Roelofsen Wim
Published: April 2006

The occurrence and localization of enzymes involved in energy supply and biosynthesis was studied in root nodules of Alnus glutinosa (L.) Vill. Vesicle clusters of the endophyte, Frankia sp., contain NADP‐dependent isocitrate dehydrogenase, succinate dehydrogenase, fumarase and malate dehydrogenase. The data indicate that both the endophyte and the host are capable of metabolizing carbon compounds via the tricarboxylic acid cycle. Both vesicle clusters of the endophyte and root nodule cells contain glutamate‐oxaloacetate transaminase which can function in a malate‐aspartate shuttle. This might enable transport of reducing equivalents from the host cell cytoplasm to the endophyte.
Effects of different gibberellins on elongation growth under short day conditions in seedlings of Salix pentandra
Authors: Junttila Olavi
Published: April 2006

Fifteen different gibberellins (GA's) were tested for their ability to induce elongation growth under short day conditions in seedlings of Salix pentandra L. GA's were applied either to the apex or they were injected into a mature leaf. GA3 was highly active and also GA4+7 and GA4 showed high activity. GA1, GA2, GA5, GA9, GA13, GA20, GA36 and GA47 showed moderate activity. GA16, GA17, GA27 and GA41 exhibited low or no activity in doses up to 10 μg per plant. In general, a better growth response was obtained with an application to the apex than with an injection into the leaf.
Effect of salicylic acid on nitrate reductase activity in maize seedlings
Authors: Jain Abha , Srivastava H. S.
Published: April 2006

The effect of different concentrations of salicylic acid on total Kjeldahl nitrogen and nitrate reductase activity in the maize (Zea mays L.) seedling was studied. The total nitrogen of the maize embryonic axis (root + shoot) from seedlings raised with 10 mM Ca(NO3)2 for 5 days was substantially higher than that from the control when 0.01 mM salicylic acid was supplied. As supply of high (1 mM) concentrations of salicylic acid decreased the accumulation of organic nitrogen. The in vivo activity of nitrate reductase in the roots increased at low concentrations of salicylic acid, while high concentrations were inhibitory. The stimulative concentration of the acid protected in vivo loss of nitrate reductase activity under non‐inducing conditions, whereas it had no effect on in vitro loss of enzyme. It is suggested that salicylic acid increases in vivo enzyme activity indirectly, to some extent by protecting the natural inactivation of the enzyme.
Effects and interactions of gibberellic acid and cytokinins on the retention of chlorophyll and phosphate in barley leaf segments
Authors: Sabater Bartolome , Rodriguez Maria Teresa , Zamorano Antonio
Published: April 2006

In leaf segments of barley (Hordeum vulgare L. cv. Mozoncillo), the cytokinin specificity for retarding the loss of phosphate is different from that of retarding the loss of chlorophyll. Some cytokinins require the simultaneous application of gibberellins to delay the loss of phosphate. Although both chlorophyll and phosphate losses occur in senescence, they are apparently controlled by cytokinins through different mechanisms.
Effects of light, temperature and nitrogen treatments upon the fatty acid composition of galactolipids of young and older leaves from winter rape plants
Authors: Diepenbrock W.
Published: April 2006

The influences of light (1.5 W m−2, 24 W m−2), temperature (5°C, 15°C, 25°C) and nitrogen nutrition (1 mmol 1−1 NH4NO3, 2 mmol 1−1 NH4NO3, 8 mmol 1−1 NH4NO3) treatments on the fatty acid composition of galactolipids from young and older leaves of oil‐seed rape (Brassica napus L. var oleifera cv. Quinta) were tested. The linolenic acid (18:3) content of lipids from young leaves was mainly affected by light and temperature. However, older leaves reacted in the first instance on nitrogen and light. For young leaves a significant light/temperature interaction was obvious. The highest level of 18:3 (72%) was observed at 5°C/1.5 W m−2. Changes in the fatty acid composition in older leaves indicated a retarded senescence by an increased nitrogen‐supply. The 8 mmol 1−1 NH4NO3/24 W m−2 treatment resulted in the highest percentages of unsaturated fatty acids. The results are discussed in relation to the importance of the first‐order interaction of environmental factors to the galactolipid fatty acid composition. Additionally, the relevance of leaf‐age has been stressed.
Effects of applying etnylene to the root system of Zea mays on growth and nutrient concentration in relation to flooding tolerance
Authors: Jackson Michael B. , Drew M. C. , Giffard Susan C.
Published: April 2006

Previous studies have shown increases in the concentration of ethylene in the soil and roots of plants when the soil is water saturated (flooded). In Zea mays L. this occurs in association with an overall reduction in growth but without extensive foliar senescence and in conjunction with the development of an adventitious root system. We have assessed the possibility that ethylene may be involved in these responses to flooding. Mixtures of the gas in air were therefore supplied to the roots and stem‐base of Z. mays growing in nutrient solution.

Seven or 14 d exposure to ethylene (1 or 5 νl 1−1) inhibited seminal root elongation and growth in dry weight and accelerated the emergence of adventitious roots, although their final length and dry weight were depressed. Leaf extension was inhibited by 0.1,1.0 or 5.0 μl 1−1 ethylene around the roots; leaves extending rapidiy at the start of treatment were the most sensitive. Final shoot fresh and dry weights were depressed by the gas but tie shootrroot dry weighl ratio and percentage dry matter were not affected greatly. Leaf chlorosis was not observed but the concentration of phosphorus in the shoots was 26 to 31% below normal.

When aeration of the nutrient solution was stopped, the concentration of dissolved oxygen declined and the concentration of ethylene in the roots increased. Similar changes occur in response to soil flooding. Root and shoot growth was slowed by non‐aeration although the shootroot dry weight ratio remained unchanged. The phosphorus concentration of the shoots was depressed but there was little chlorosis or leaf death. The similarity in these respects between the effects of ethylene and non‐aeration suggests that in flooded Z. mays, ethylene contributes to their development by accelerating the emergence of adventitioos roots, inhibiting phosphorus accumulation in the shoots and by a non‐toxic inhibition of plant growth.
Effect of water stress on some oxidative enzymes and senescence in Vigna seedlings
Authors: Mukherjee S. P. , Choudhuri M. A.
Published: April 2006

Seedlings of Vigna catjang Endl. were subjected to water stress for 6, S and 10 days by withholding water to investigate the activities of some oxidative enzymes and the pattern of senescence in leaves of 17‐day‐old seedlings undergoing water stress. Increasing duration of stress produced a proportional increase in the activities of IAA‐oxidase, AA‐oxidase, peroxidase and glycolate oxidase but decreased catalase activity and the contents of both chlorophyll and protein, hastening senescence. Leaf water potential and relative water content were also lowered with incresing duration of stress. Permeability was increased in leaf tissue undergoing water stress for 8 days. Seed treatment with CaCl2 (10−2 and 10−14M) for 6 h improved the water status of leaves, decreased tissue permeability, activities of oxidative enzymes, decline of chlorophyll and protein contents and delayed senescence compared to untreated water stressed plants.
Intervention de l'oxygène atmosphériqoe sur l'absorption d'eau chez Helianthus annuus
Authors: Lascève G. , Couchat Ph.
Published: April 2006

The role of atmospheric oxygen on root water absorption in Helianthus annuus. The effect of atmospheric anoxia on root water absorption was studied. The experiments were carried out on intact young sunflowers in controlled temperature, light and gas environment; roots were kept in aerated nutrient solution at constant temperature. The evolution of root water absorption and transpiration rate was measured continuously. Before the experiment, the plant was preconditioned at a high transpiration rate by illumination or by CO2 free air in darkness. Then the atmospheric oxygen was suppressed for 1 h, after which the normal conditions were restored.

In anoxia and darkness, the root water absorption cannot balance transpiration, so that an important water stress develops in the plant; the light compensates this effect through the photosynthetic oxygen. The supply of oxygen, in darkness or in light, immediately removes inhibition of stomatal closure and of root water absorption. Two mechanisms control water absorption by roots: the fast one occurs in the leaves and the slower one cannot develop without the root system.
Influence of O2‐ and CO2‐concentrations on oscillations in the transpiration rate from oat plants in darkness
Authors: Klockare Rune , Falk Stig Olof
Published: April 2006

The effect of changed O2‐ and CO2‐concentrations in air on oscillations in the transpiration rate of young oat plants in darkness has been investigated. Lowering the O2‐concentration to 5% did not affect the oscillations. When the CO2 in the air was removed, the transpiration rate increased, and the oscillations ceased. When the CO2‐concentration was raised to 0.3 or 3% the transpiration rate temporarily decreased, but the period of the oscillations was not changed. Further increase of the CO2‐concentration caused, after a temporary decrease, an increased transpiration rate, and the oscillations eventually ceased. The period of the oscillations was influenced by the temperature: a lower temperature gave a longer period. It is concluded that substomatal O2‐deficit or high CO2‐concentration do not play a crucial role in the origin of these oscillations.
Role of sugars in nitrate utilization by roots of dwarf bean
Authors: ten Cate Charlotte H. Hänisch , Breteler Hans
Published: April 2006

Nitrate uptake and in vivo, nitrate reductase activity (NRA) in roots of Phaseolus vulgaris, L. cv. Witte Krombek were measured in nitrogen‐depleted plants of varying sugar status, Variation in sugar status was achieved at the start of nitrate nutrition by excision, ringing, darkness or administration of sugars to the root medium.

The shape of the apparent induction pattern of nitrate uptake was not influenced by the sugar status of the absorbing tissue. When measured after 6 h of nitrate nutrition (0.1 mol m−3), steady state nitrate uptake and root NRA were in the order intact>dark>ringed>excised. Exogenous sucrose restored NRA in excised roots to the level of intact plants. The nitrate uptake rate of excised roots, however, was not fully restored by sucrose (0.03–300 mol m−3).

When plants were decapitated after an 18 h NO3− pretreatment, the net uptake rate declined gradually to become negative after three hours. This decline was slowed down by exogenous fructose, whilst glucose rapidly (sometimes within 5 min) stimulated NG−3 uptake. Presumably due to a difference in NO3− due to a difference in NO3− uptake, the NRA of excised roots was also higher in the presence of glucose than in the presence of fructose after 6 h of nitrate nutrition. The sugar‐stimulation of, oxygen consumption as well as the release of 14CO2 from freshly absorbed (U‐14C) sugar was the same for glucose and fructose. Therefore, we propose a glucose‐specific effect on NO3− uptake that is due to the presence of glucose rather than to its utilization in root respiration. A differential glucose‐fructose effect on nitrate reductase activity independent of the effect on NO3− uptake was not indicated.

A constant level of NRA occurred in roots of NO3− induced plants. Removal of nutrient nitrate from these plants caused an exponential NRA decay with an approximate half‐life of 12 h in intact plants and 5.5 h in excised roots. The latter value was also found in roots that were excised in the presence of nitrate, indicating that the sugar status primarily determines the apparent rate of nitrate reductase decay in excised roots.
On the biogenesis of cytokinins in Lactobacillus acidophilus ATCC 4963
Authors: Helbach Max , Klämbt Dieter
Published: April 2006

The biosynthesis of free cytokinins in the mevalonic acid auxotrophic Lactobacillus acidophilus, ATCC 4963 has been investigated. After a short pulse labelling with [14C]‐mevalonic acid the labelled free cytokinins of bacteria and media and the labelled cytokinin‐nucleotide moiety of tRNA and oligonucleotides were determined and compared. tRNA is the main precursor for cytokinin production. Bacteria previously starved for mevalonic acid showed the presence of at least one additional cytokinin precursor. A fraction of oligonudeotides shows rapid incorporation of 14C and contains labelled cytokinin nucleotides. There are no indications for a direct isopentenylation of adenine, adenosine or its phosphate derivatives.
Effects of supplemental UV‐B radiation on growth and leaf photosynthetic reactions of soybean (Glycine max)
Authors: Vu C. V. , Allen L. H. , Garrard L. A.
Published: April 2006

Experiments were conducted under greenhouse conditions to investigate the effects of enhanced UV‐B radiation (280 to 320 nm) on height, fresh and dry weights, leaf chlorophyll and carotenoids, CO2 uptake rates, and Hill activity in soybean (Glycine max L. cv. Bragg). Plants were exposed for 6 h continuously from midmorning to midafternoon each day to UV‐B radiation which was provided by Westinghouse FS‐40 sun lamps filtered with 0.127‐mm cellulose acetate film (UV‐B enhanced) or 0.127‐mm Mylar S film (UV‐B Mylar control). Three different UV‐B enhanced radiation levels were tested: 1.09 (treatment T1), 1.36 (treatment T2), and 1.83 (treatment T3) UV‐B sun equivalent units (UV‐Bsec) where 1 UV‐Bsec= 15.98 mW·m−2 of solar UV‐B obtained by applying EXP ‐[(α‐265)/21]2, a weighting function that simulates the DNA absorption spectrum, to the UV‐B lamp systems. These UV‐B levels correspond to a calculated decrease in stratospheric ozone content of 6%, 21%, and 36% for treatment T1, T2, and T3, respectively.

Daily exposure of soybean plants to UV‐B radiation significantly decreased height, fresh and dry weights, leaf chlorophyll and carotenoid contents, and CO2 uptake rates. Leaf pigment extracted in 80% acetone from UV‐B‐treated soybean plants showed considerable increase in absorption in the wavelength region of 330 to 400 nm with increased UV‐B radiation levels. Chloroplast preparations from leaves of T2 and T3 plants showed significant reductions in Hill reaction measurements.
Availability of water and inorganic nutrients in the persistent leaf bases of the grasstree Kingia australis, and uptake and translocation of labelled phosphate by the embedded aerial roots
Authors: Lamont Byron
Published: April 2006

Numerous lateral branches of the concealed aerial roots of the grasstree Kingia australis ramify through the persistent leaf bases, suggesting a role in uptake of water and nutrients localed up to 8 m above ground. These leaf bases were shown to hold up to more than three times their weight in water. Water and nutrients (N, P and K) available in the leaf bases may greatly exceed that in an equal volume of surface soil, especially during the dry summer months. At this time, 32P injected# among the leaf bases is strongly absorbed by the aerial roots and translocated to the meristematic regions of other laterals beneath the point of application, but mostly to the stern and leaves above it. Scattered vascular bundles in the pith are the major routes for the rapid distribution of “P up and down the trunk following its departure from the aerial roots. Water and nutrients stored in the leaf bases and their subsequent uptake by the associated aerial roots may therefore contribute significantly to this species’ tolerance of long summer droughts and extremely impoverished soils.
Distribution and metabolism of root‐applied cytokinins in Pisum sativum
Authors: Morris David A.
Published: April 2006

When N6 [8–14C] furfuryladenine was applied to the intact root system of Pisum sativum L. cv. Meteor seedlings it was almost completely metabolised to other compounds within 24 h. Of the total activity recovered from the plants 94.5% was retained in the root system itself. 14C was recovered in a number of ethanol‐soluble compounds and in ribonucleic acid, deoxyribonucleic acid and protein fractions of roots, stems, leaves and axillary buds. In rapidly growing axillary buds released from apical dominance by removal of the shoot apex the combined nucleic acid fractions accounted for 63.3% of the total 14C recovered from these organs. Xylem exudate collected from decapitated plants 0 to 12 h after supplying N5[8–14C]furfuryladenine to the roots consistently contained a single major 14C‐labelled compound which, in three different solvent systems, had the same Rf values as a major endogenous cytokinin isolated from the xylem of unlabelled plants. The content of N6 [8–14C] furfuryladenine itself in the xylem exudate was always low and in some experiments it could not be detected.

It is suggested that part of the label from N6 [8‐ 14CJfurfuryladenine taken up by the intact root system may have become incorporated in an endogenous cylokinin before export to the shoot.
Glucose measurement errors in enzymic starch hydrolysates at high enzyme‐glucose weight ratios
Authors: Haissig Bruce E. , Dickson Richard E.
Published: April 2006

The 3,5‐dinitrosalicylic acid (DNS), o‐toluidine, and glucose oxidase methods accurately measured concentrations of standard glucose solutions in the absence of the starch hydrolyzing enzymes Diazyme (amyloglucosidase) and Clarase (α‐amylase). In the presence of high enzyme concentrations, particularly at low glucose concentrations, glucose oxidase and o‐toluidine somewhat underestimated standard glucose concentrations while DNS overestimated the glucose concentration by 100%. DNS also overestimated glucose in hydrolysates of standard potato starch. Glucose recovery was estimated at almost 200% of that given by glucose oxidase when enzyme starch weight ratios were 9:1 or more. Glucose was underestimated by o‐toluidine in starch hydrolysates in the presence of Diazyme at high enzyme‐starch weight ratios. DNS similarly overestimated glucose in starch hydrolysates from white spruce (Picea glauca (Moench.) Voss) and some other species, as enzyme‐starch weight ratios increased. The o‐toluidine and glucose oxidase reactions were more reliable. Overestimation of the DNS reaction was not improved by treating the glucose‐enzyme solutions with anion or cation exchange resins or by removing the enzyme prior to measurement.
Effects of amino and sulfhydryl reactive agents on respiration and ethylene production in tomato and apple fruit discs
Authors: Forney Charles F. , Arteca Richard N. , Wallner Stephen J.
Published: April 2006

We have examined the effects of the enzyme inhibitors 2,4,6‐trinitrobenzene sulfonic acid (TNBS) and 5,5′‐dithiobis‐2‐nitrobenzoic acid (DTNB) on ethylene and CO2 production in apple and tomato fruit discs. In the past these inhibitors have been used to inhibit membrane bound enzyme systems in various animal tissues. The amino reactive inhibitor TNBS was shown to decrease ethylene production in tomato discs without affecting rates of respiration; similar results were obtained with apple. The effects of the sulfhydryl reactive inhibitor DTNB were not as clearcut as TNBS. There was little effect of DTNB on ethylene production in tomato discs, however, in apple discs ethylene production was significantly reduced. DTNB also reduced the respiration rate in apple discs, although not to the same extent as ethylene production. The inhibition of DTNB was reversed by a brief treatment with dithioerythritol. The results indicate that ethylene production takes place at the cell surface.
The buckling of plant roots
Authors: Whiteley G. M. , Hewitt J. S. , Dexter A. R.
Published: April 2006

The mechanical stresses required to buckle root tips were measured directly for seven plant species. For two of these, both seminal and primary lateral roots were measured. For four of the plant species investigated, the easier and more rapid method used to measure the buckling stresses of excised root tips gave results which agree closely with those obtained for the growing roots of intact plants. Values of buckling stress were also calculated from previously determined elastic properties of roots. The calculated and measured values of buckling stress are of the same magnitude only, and comparison for ten root types fails to show any consistent relationship between these two methods. From the results from three plant species it has been possible to define empirical functions to account for the observed changes in root buckling stress with air gap length and water stress. Buckling stresses are not significantly affected by the concentration of nitrate in the growth medium.
Photo‐oxidative damage in the ripening tomato fruit: Protective role of superoxide dismutase
Authors: Rabinowitch Haim D. , Sklan David , Budowski Pierre
Published: April 2006

Factors relating to photo‐oxidative damage in tomatoes were investigated during maturation of the fruit and upon induction of sunscald. Superoxide dismutase (SOD) activity passed through a minimum at the mature‐green and breaker stages of ripening and availability of zinc and copper did not appear to be a limiting factor in the synthesis of the enzyme. Iron levels were maximal and total carotenoid concentrations were lowest during the same mature‐green and breaker stages of maturation, while chlorophyll was starting to decrease but was still present in large amounts. Peroxidase activity decreased steadily during ripening. Artificial induction of tolerance to photodynamic damage by controlled heat treatment was accompanied by an increase in SOD activity, while carotenoid levels and peroxidase activity did not change. These findings support the thesis that the previously reported susceptibility of tomatoes to photodynamic damage, i.e. sunscald, during the mature‐green and breaker stages of maturation is related to enhanced formation of superoxide ions, at a time when chloroplast structure begins to break down. SOD, by scavenging the superoxide, appears to supplement the protective action of carotenoids against photo‐oxidative injury.
Identification of phenylacetic acid as a natural auxin in the shoots of higher plants
Authors: Wightman Frank , Lighty Douglas L.
Published: April 2006

Evidence indicating the natural occurrence of the auxin substance, phenylacetic acid (PAA), in a range of crop plants has been obtained from paper chromatography followed by bioassay and from HPLC and GLC analysis of acidic ether extracts from vegetative shoots of these plants. Confirmatory evidence for the presence of PAA in tobacco shoots has been obtained from GC‐MS analysis. Quantitative estimation of the relative amounts of the two auxins, IAA and PAA, in the different shoot extracts was achieved by paper chromatography followed by gas chromatography. The amount of PAA in all six plants was found to be several times greater than that of IAA and calculation of average internal concentrations revealed that PAA is present in vegetative shoots at physiologically active concentrations. Present knowledge of the growth‐regulating activity of this new natural auxin is discussed.
Differential effects of benzyladenine and potassium on DNA, RNA, protein and chlorophyll contents and on expansion growth of detached cucumber cotyledons in the dark and light
Authors: Haru Kunimaro , Naito Kunihiko , Suzuki Hiroshi
Published: April 2006

Benzyladenine (BA) and KCl were applied to detached cucumber (Cucumis sativus L. cv. Ohio) cotyledons in continuous light or in the dark with subsequent light. BA brought about an increase in fresh weight and in DNA, RNA and carotenoid contents in both treatments. KCl did not cause an increase in fresh weight and cellular constituents in the dark, but it did result in an increased fresh weight and DNA content after illumination or in continuous light. BA + KCl treatment resulted in increased carotenoid and DNA contents in the dark, and in increases in fresh weight and all cellular constituents upon subsequent exposure to light. The effects of BA and BA + KCl on growth and chlorophyll synthesis decreased with cotyledon age.

BA pretreatment in the dark eliminated the lag phase in chlorophyll synthesis and increased the rate of synthesis. Treatment in continuous light had little effect. KCl did not shorten the lag phase in chlorophyll synthesis, but it stimulated the rate of synthesis in the light. Dark pretreatment with BA + KCl markedly increased the effect of BA on chlorophyll synthesis. Chlorophyll content and fresh weight were higher in cotyledons treated with BA followed by KCl than in cotyledons treated in the reverse order. These results suggest that growth and greening in cucumber cotyledons are primarily controlled by BA and that KCl intensifies the BA effect after irradiation.
Internode length in Pisum. I. The effect of the Le/le gene difference on endogenous gibberellin‐like substances
Authors: Potts Wendy C. , Reid James B. , Murfet Ian C.
Published: April 2006

Tall peas (Pisum sativum L.) contain a relatively large amount of a polar gibberellinlike substance(s) which is either absent or present in only small amounts in dwarf peas. This biochemical difference can be attributed to a genetic difference at the le locus. Preliminary results using unrelated pure breeding tall (Le) and dwarf (le) lines were confirmed by the use of an F2 progeny segregating for the Le/le pair of alleles. The polar gibberellin‐like substance(s) in tall peas is located mainly in the actively growing and elongating apical region of the shoot. The level of this substance(s) is much reduced in mature stem and leaf tissue. The gibberellin‐like substance(s) in question remains unidentified although it can be characterised by activity in both the lettuce hypocotyl bioassay and the rice seedling bioassay. The dwarf rice cultivars ‘Tan‐ginbozu’ and ‘Waito C’ are both sensitive. The magnitude of the other major zone of gibberellin‐like activity (the GA20‐like zone) did not vary greatly between tall and dwarf segregates but the apical regions of the shoots again contained significantly more activity than the mature regions.
The effect of the different components of the inhibitor β complex in peelings of resting potato tubers on the respiration and uptake of inorganic phosphate
Authors: Franklin Jeevalatha , Hemberg Torsten
Published: April 2006

The four different inhibitors or groups of inhibitors, called I, II, IV and V, which could be separated from the inhibitor β complex from peelings of resting potatoes (Solanum tuberosum L., variety Majestic) by thin layer chromatography in chloroform: 96% acetic acid (95:5 v/v), stimulated the oxygen uptake of discs of potato tubers during the first 4 to 5 h after addition of the substances. Number I was less active, the other three more active. Furthermore II, IV, and V significantly inhibited the uptake of inorganic phosphate by potato discs measured 24 and 5 h after addition of the substances, so that they seem to be uncouplers of oxidative phosphorylation.
Protein kinase associated with chromatin and changes in substrate‐specificity during germination of wheat seeds
Authors: Sasaki Kimiko , Sugita Mamoru
Published: April 2006

Protein kinase activity was associated with chromatin in wheat (Triticum aestivum L. cv. Mukakomugi) embryos. The kinase activity did not change significantly during germination, whereas the activity of poly (ADP‐ribose) synthetase decreased significantly. The protein kinase activity in chromatin was inhibited by NAD, NADH, and ADP‐ribose, and was enhanced by treatment of the chromatin with snake venom phosphodiesterase or soybean trypsin inhibitor. The activity in chromatin was not stimulated by cyclic AMP. Different subfractions of the histones, H1 and H2, were mainly phosphorylated in germ and 3 day‐germinated seedling chromatins. The histones, H3 and H4, seemed unable to accept phosphate from ATP in the in vitro reaction system. Different acidic non‐histone chromosomal proteins were phosphorylated in germ and 3‐day‐germinated seedling chromations, and germ‐specific and seedling‐specific acidic non‐histone chromosomal proteins seemed unable to accept phosphate from ATP.
Biochemical changes during germination and seedling growth in Cuscuta campestris
Authors: Charles Denys J. , Singh Madhav , Sanwal G. G.
Published: April 2006

Changes in the contents of starch, protein, DNA, RNA, total phosphorus, acid soluble phosphorus and inorganic phosphorus, and in the activities of some enzymes of carbohydrate, amino acid, nucleic acid and phosphate metabolism were studied during the germination of Cuscuta campestris seeds. The results are expressed on per seed basis.

Starch content in Cuscuta seeds showed a steady decline with most of it depleted by the end of the eighth day of germination. Protein content increased with germination up to 48 h and then decreased. RNA and DNA contents increased to a maximal level on the fourth day of germination and then decreased. Total phosphorus in the seeds remained almost unchanged during the period of study. Both trichloroacetic acid soluble and inorganic phosphorus increased until the third day and then decreased. Phytin was rapidly hydrolyzed with little being detectable by the seventh day of germination. Glucose‐6‐phosphate dehydrogenase increased with germination, while fructose bisphosphate aldolase which is indispensable for glycolysis, decreased with germination. Ribonuclease and deoxyribonuclease increased till the third and fourth day, respectively, and then decreased. Aspartate and alanine aminotransferases showed a maximum on the second day and then decreased. Activities of alkaline fructose‐1,6‐bisphosphatase and phytase were absent in the dry seeds and appeared only on the second day of germination. Both α‐ and β‐amylase activities were present in the dry seed.
Guidelines for measuring and reporting environmental conditions in controlled‐environment studies
Authors: Krizek Donald T.
Published: April 2006

Guidelines for measuring and reporting environmental conditions in plant growth chambers are presented in tabular form. These guidelines are recommended by the North Central Region (NCR‐101) Technical Committee on Growth Chamber Use, a committee formed under the Cooperative Research Program of the State Agricultural Experiment Stations (SAES) and the United States Department of Agriculture (USDA). Recommendations on location and frequency of measurements as well as suggested format and units of measurement are listed for each environmental parameter. The adoption of these standardized guidelines should greatly improve the uniformity of research conducted in controlled environments and facilitate comparison of experimental results obtained in studies conducted in different laboratories on a world‐wide basis.
Influence of nitrogen sources on chloroplast development in wheat seedlings
Authors: Golvano M. P. , Felipe M. R. , Cintas A. M.
Published: April 2006

The effect of different nitrogen sources (ammonium, nitrate or both ions together) on plastid development in dark‐grown and illuminated seedlings of wheat (Triticum vulgare L. cv. Yecora) has been investigated. Plastids of plants grown in ammonium showed even in the dark a larger internal membrane length, higher ribulose bisphos‐phate carboxylase activity and greater content of soluble proteins than plastids of plants grown in nitrate. After the first hour of illumination rudimentary thylakoids showing some joining points were observed in the ammonium plastids. After 10 h no prolamellar bodies were seen in the ammonium plastids, and the internal plastid membrane length was greater than in the other treatments. There was no light‐induced increase in protein synthesis after illumination for 1 h. After 10 h the increase observed in protein synthesis was not followed by a response in the enzyme activity in any of the treatments. After 20 h the lag in the induction of ribulose bisphosphate carboxylase ceased, the enzyme activity and soluble proteins being higher in the leaves of ammonium seedlings than in those from nitrate. From the correlation obtained between the ultrastructural electron microscope observations and the enzymatic studies, it appears that ammonium nutrition has a positive influence on the formation of the plastid membrane system and on the onset of photosynthesis and, consequently, on the development of chloroplasts.
Gas chromatographic and GC‐MS evidence for the occurrence of 3‐indolylpropionic acid and 3‐indolylacetic acid in seedlings of Cucurbita pepo
Authors: Segal Lawrence M. , Wightman Frank
Published: April 2006

Gas chromatographic and GC‐MS evidence is presented for the occurrence of two auxin substances, 3‐indolylacetic acid and 3‐indolylpropionic acid, in hypocotyls of Cucurbita pepo cv. Golden Hubbard seedlings grown in darkness or under blue‐light illumination. The data provide the first unequivocal evidence for the presence of 3‐indolylpropionic acid in a higher plant.
Influence of sequential prolonged periods of dark and light on pinitol concentration in clover and soybean tissue
Authors: Smith A. E. , Phillips D. V.
Published: April 2006

The influence of prolonged dark periods on the concentration of pinitol in white clover (Trifolium repens L. ev. Regal Ladino) and soybean [Glycine max (L.) Merr.] tissue was investigated. Clover and soybean plants were harvested periodically throughout continuous dark periods of 40 and 44 h, respectively, followed by 24 h of continuous light. The foliage and root tissue of clover and foliage tissue of soybeans were analyzed for the concentration of glucose, fructose, sucrose and pinitol. Pinitol concentration (mg/g dry weight tissue) was unchanged by the prolonged dark period followed by 24 h of continuous light compared to tissue of plants harvested at 0‐h and plants receiving normal photoperiods. Concentrations of the carbohydrates, in the tissue were depleted by the prolonged dark period. However after 6 h of light, the concentration of these sugars increased to concentrations equal to 0‐h harvested plant tissue and tissue of plants receiving normal photoperiods. These results indicate that pinitol probably does not function as a source of reserve energy comparable to sucrose, glucose, and fructose.
The absorption and translocation of diclofop‐methyl and amitrole in wheat and oat roots
Authors: Jacobson Andrew , Shimabukuro Richard H.
Published: April 2006

The absorption and translocation of diclofop‐methyl (methyl 2‐[4(2′,4′‐dichlorophenoxy)phenoxy]propanoate) was examined by using a specially designed treatment apparatus that separated excised roots or roots of seedlings into four zones. [14C]‐Diclofop‐methyl was absorbed along the entire root length of both wheat (Triticum aestivum L.) and oat (Avena sativa L.). In both species, absorption was greatest in the apical region of the root. Absorption by the apical region of wheat roots was more than three times greater than the basal portions, and more than twice as great as the apical region of oat roots. Less than 5% of the absorbed diclofop‐methyl was translocated in both wheat and oat roots. Diclofop‐methyl and diclofop(2‐[4(2′,4′‐dichlorophenoxy)phenoxy]propanoic acid) were the predominant translocated forms. The absorption and translocation of amitrole (3‐amino‐1,2,4‐triazole) were also examined. Amitrole was absorbed along the entire length of wheat roots and translocated primatily in the basipetal direction. The usefulness of the specially designed apparatus for biochemical and physiological studies is discussed.
Effect of red light and gibberellic acid on lipid metabolism in germinating spores of the fern Anemia phyllitidis
Authors: Gemmrich Armin R.
Published: April 2006

The spores of the fern Anemia phyllitidis contain abundant quantities of lipid as reserve material. Germination of these spores can be induced either by red light or, even in the dark, by gibberellic acid. The effects of both these factors on lipid degradation, lipase and isocitrate lyase activities, and on the fatty acid composition have been studied in the course of the germination process. During germination in darkness with gibberellic acid, the fatty acid composition remained similar to that in the ungerminated spore. In contrast, when spores were germinated in red light, α‐linolenic acid was synthesized. Little activity of lipase and isocitrate lyase could be detected in the dry spore. Red light or gibberellic acid affected a dramatic increase of the activities of these enzymes. Lipid breakdown and lipase activity were more active in red light, however. Permanent stimuli were necessary for growth and complete lipid degradation. Induction of germination simultaneously with both factors revealed an additivity of the effects of red light and gibberellic acid.