bluuebunny/crossref_metadata_2025 huggingface dataset:
The Water Balance of Cut Rose Flowers
Authors: MAYAK S. , HALEVY A. H. , SAGIE S. , BAR‐YOSEPH A. , BRAVDO B.
Published: April 2006

A sharp decline in water potential of petal tissue associated with wilting of cut rose flowers is described. Such a decline did not develop in senescing intact flowers. A circadian rhythm in water absorption by cut flowers was observed.

The decline in fresh weight observed in the last phase of the vase life of cut flowers occurred earlier in a short‐lived cultivar than in a longer‐lived one. A decline in potential conductivity to water was observed with time in stems of cut roses. Concomitantly cellulase activity increased after cutting. Flowers held in cellulase solution wilted earlier than the controls. However, no difference was found in these two parameters between two cultivars differing in their longevity. The difference in longevity between the two cultivars was large especially under conditions promoting high transpiration rates, and was narrowed when flowers were either held in mild conditions, or the leaves were stripped off.

Although stomates were equally open in intact flowers of the two cultivars, in cut flower shoots of the short‐lived cultivar stomates were more widely open. In accordance transpiration rates were higher, and wilting occurred earlier in the short‐lived cultivar than in the long‐lived one. It is concluded that the earlier wilting of cut flowers of the short‐lived cultivar is mainly due to lower ability to close stomates in response to water stress conditions, and not to earlier formation of vascular blockage.
Further Studies on the Relationship between Growth Regulators and Tuberization of Dahlias
Authors: BIRAN I. , LESHEM B. , GUR I. , HALEVY A. H.
Published: April 2006

Abscisic acid (ABA) and gibberellin (GA) treatments, applied to budless leaf cuttings of Dahlia under long day conditions, did not increase the total weight of the cuttings but did affect the region where photosynthates accumulate. GA treatment inhibited the growth of tubers and roots, and enhanced thickening at the petiole base. ABA did not affect the weight of roots or petiole, but promoted the growth of tuberous roots. Anatomical examination of the tuberization revealed that it is caused by inter‐fascicular cambial activity producing parenchyma cells inward. No anatomical difference could be observed between the GA‐induced thickening at the petiole base and the natural or ABA‐induced thickening of the roots. In single node cuttings, taken from various sites along the branch, tuberization ability increased with proximity to the base of the branch, where axillary buds are more inhibited.

Short‐day conditions which promote tuberization, increased the endogenous level of ABA‐like inhibitors in intact plants. External conditions and growth substances which inhibit growth also inhibited tuberization. Benzyladenine treatments did not affect tuberization.

It is suggested that in addition to their respective indirect effects via the enhancement or suppression of top growth, GA and ABA directly control tuberization. ABA levels which increased under short‐day conditions seem to produce a sink in the roots. GA probably inhibits tuberization by interfering with the trans‐location of photosynthates to the root area.
Role of Ethylene in Induction of Flooding Damage in Sunflower
Authors: KAWASE MAKOTO
Published: April 2006

The possibility that symptoms of flooding damage in plants are primarily caused by an accumulation of ethylene was investigated using pot‐grown sunflower (Helianthus annuus) plants.

When plants were flooded to the basal pairs of leaves, ethylene in roots and stems below the water line began to increase. This coincided with the start of hypocotyl hypertrophy and new root formation in hypocotyls, which continued for 14‐16 days. There were highly significant correlations between ethylene concentration and number of roots and hypocotyl diameter.

After approximately 4 days of flooding, ethylene concentrations in stems between nodes for the 1st and 3rd basal pairs of leaves started to increase, coinciding with initiation of chlorophyll breakdown and epinasty of the 2nd basal pairs of leaves. Thus, there were correlations between ethylene concentration and chlorophyll breakdown and epinasty. The lower the leaves, the more chlorophyll breakdown among 1st, 2nd, 3rd, and 4th basal pairs of leaves. The longer the flooding, the more severe the flooding damage; and even when returned to normal condition, plants flooded longer than 3 days were not able to recover from flooding damage.

A gas chromatographic study revealed that Ethephon was absorbed by roots and decomposed to ethylene in the plant. Damage symptoms caused by soil application of Ethephon, such as reduced stem height, chlorophyll breakdown, epinasty of the 2nd basal pairs of leaves, and hypocotyl hypertrophy, were almost identical with those caused by soil flooding treatment.

Microscopic studies revealed that radially enlarged cells and increased intercellular spaces in the cortex were the major contribution to the increased hypocotyl diameter in both flooded and Ethephon‐treated plants.

It is concluded that the increase in ethylene concentration in flooded plants is largely, although not exclusively, responsible for flooding damage symptoms.
Regulation of Growth in Avena (Oat) Stem Segments by Gibberellic Acid and Abscisic Acid
Authors: KAUFMAN PETER B. , JONES RICHARD A.
Published: April 2006

The purpose of this study was to analyze the nature of the interaction between gibberellic acid (GA3) and abscisic acid (ABA) in the regulation of growth in excised Avena (oat) stem segments. Growth, compared to sucrose controls, was inhibited by ABA in the range of 10−4 to 10−6M. GA3‐promoted growth was also inhibited by ABA in the same concentration range. A Lineweaver‐Burk analysis of the interaction between GA3 and ABA indicated that ABA acts in a non‐competitive fashion with GA3. This same result was obtained previously with GA3‐indoleacetic acid (IAA) and GA3‐kinetin interactions with Avena stem sections. Our results indicate that ABA can inhibit GA3‐promoted growth within physiological concentrations, and that it is probably acting at a different physiological site from that for GA3.
Effect of Temperature and Kinetin on the Germination and Endogenous Hormones of Hyoscyamus muticus Seeds
Authors: ELKINAWY MAHASEN , HEMBERG TORSTEN
Published: April 2006

Germination of Hyoscyamus muticus L. seeds was investigated under different temperature, light and kinetin treatments. Diurnal temperature fluctuation of 25°C for 14 h and 5°C for 10 h, strongly promoted germination. Kinetin (60 mg/1) substituted for the periodic temperature changes. Both kinetin and diurnal temperature fluctuation increased the IAA level in the seeds prior to germination. A natural inhibitor (Rf 0.6–0.8) did not disappear in response to either treatment.
Isoperoxidase Activity and Induction in Cultured Tissues of Wild Carrot: a Comparison of Proembryos and Embryos
Authors: Wochok Zachary S. , Burleson Brent
Published: April 2006

Several anodic isoperoxidases were found in embryonic tissues of cultured wild carrot, Daucus carota L., which were not present in the proembryo masses from which they originate. This difference is further reflected in the higher specific activity of peroxidase in embryo extracts as compared to proembryonic tissues. The absence of anodic isoperoxidases and depressed peroxidase activity in carrot tissue cultures in the presence of 2,4‐dichlorophenoxyacetic acid (2,4‐D) suggests a regulatory role for this plant growth regulator in controlling peroxidase activity.
Control of the Light Saturation Point for Photosynthesis in Tomato
Authors: MILES C. D.
Published: April 2006

The light saturation curves for photosynthesis in Lycopersicon esculentum have been studied for a yellow‐green mutation and for hormone treated plants. Comparisons have been made between saturation point and the size of the photosynthetic unit in these plants. These data suggest a function in the regulation of photosynthetic rates.
Effects of Varying Light Intensities and Temperature Treatments Applied to Whole Plants, or Locally to Leaves or Flower Buds, on Growth and Pigmentation of ‘Baccara’ Roses
Authors: BIRAN I. , HALEVY A. H.
Published: April 2006

Varying light intensity and temperature treatments were applied to whole plants, or to the leaves, or to the flower buds of ‘Baccara’ roses. The effect of these treatments on flower dimensions and pigmentation of the petals was examined.

Cooling only the leaves had no effect; cooling only the buds enhanced both bud weight and pigmentation, but the effect was less marked than when the whole plant was cooled. Reducing plant temperature by misting with desalinated water enhanced both pigmentation and flower size.

Darkening of only the leaves, or their removal, resulted in an inhibition of the pigmentation and also in a decrease in bud weight. Darkening of only the flower bud did not affect either pigmentation or bud weight, but caused bud elongation. It is suggested that light intensity and temperature affect flower growth and pigmentation via their effects on the availability of sugars in the flower bud.
Effects of Short‐Term Heat and Shade Treatments on Petal Colour of ‘Baccara’ Roses
Authors: BIRAN I. , HALEVY A. H.
Published: April 2006

Growth and pigmentation of ‘Baccara’ rose buds were followed. Petal elongation mainly occurred during a short period of time after the flowering shoot had stopped elongating. Approximately 90% of the flower pigments were synthesized during a short period lasting from the time the bud was 75% to the time it was 100% of its diameter at opening time. Petal growth continued after this period so that the pigments in the petal were “diluted”. Heat stress applied to whole plants or to flower buds only, or a short duration of low light intensities caused “blueing” of the petals when these conditions prevailed during the period of maximum pigmentation. Stress conditions prior to this period or following it, had no effect. We suggest that stress conditions such as high temperature or low light intensities reduce the availability of sugars. When this occurs at the time of maximum pigment production, a fall in the level of pigment occurs, which results in the “blueing” of the petals.
Glutamic Dehydrogenase and Glutamic‐oxaloacetic Transaminase in Apple Tree Tissues
Authors: COOPER D. R. , HILL‐COTTINGHAM D. G.
Published: April 2006

A technique is described whereby active preparations of glutamic dehydrogenase (GDH) and glutamic‐oxaloacetic transaminase (GOT) can be obtained from all apple tree tissues using a hand‐operated coffee mill. The amount of insoluble polyvinylpyrrolidone required and the composition of the extractant have been investigated together with the degree of replication obtained and the stability of the resultant extracts.

After extraction of all tissues the proportion of both GDH and GOT found in the supernatant was far greater than that in the mitochondria. Addition of calcium and some other metal ions to the assays resulted in some increase in GDH but had no effect on GOT activity. With crude extracts the effect of added calcium was small but after ultrafiltration or acid precipitation it was greatly increased.

The co‐factors NADH, NADPH and NAD were all active with GDH in extracts of apple leaves, stem bark and roots. No activity was found with NADP. In the presence of added calcium ions the ratios of activity NADH:NADPH and NADH:NAD were approximately 10:1 and 20:1 respectively.

The seasonal variations in specific activity of GDH and GOT in apple leaves, stem bark and wood, and old and young roots were determined separately. The highest GDH activities were found in the leaves in October and in the stem bark in May, while in other tissues activities were generally higher in winter than in summer. The seasonal patterns for GOT activity were very similar to those for GDH except that in the leaves the level changed little through the year.

The results are discussed in relation to published work on these enzymes in other plants and to their possible role in the apple tree.
Intensity of Bud Dormancy in Douglas‐fir and Its Relation to Scale Removal and Rooting Ability
Authors: ROBERTS A. N. , TOMASOVIC B. J. , FUCHIGAMI L. H.
Published: April 2006

Uniform 1‐ or 2‐year‐old rooted cuttings of 3 Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco, clones were grown under natural conditions in containers from July 1, 1971 to February 15, 1972. At 2‐week intervals, plants from this natural temperature and daylength environment were moved into controlled, long day (LD‐18 h) and short day (SD‐9 h) environments to measure the intensity of bud dormancy from its inception to termination based on number of days to bud break and percentage of expanding buds on a given date. Growth responses to bud scale removal were also helpful in describing the degree and nature of bud dormancy. The cessation of initiatory activity at the bud apex, reflected in the needle number of the subsequent growth flush, corresponded to a September peak of bud dormancy based on the number of days to bud break in the LD environment. Similarly, the cold requirement for breaking bud dormancy was measurable in the SD environment. The use of such rest intensity indices is illustrated in the close relationship established between bud dormancy development and stem cutting rooting ability.
In vitro Plant Formation from Stem Explants of Rape (Brassica napus cv. Zephyr)
Authors: KARTHA K. K. , GAMBORG O. L. , CONSTABEL F.
Published: April 2006

Internodal segments from 6‐weeks‐old rape plants (Brassica napus L. cv. Zephyr) were induced to differentiate in vitro producing shoots or shoots and roots on synthetic nutrient medium under controlled conditions. Benzyladenine (BA) alone (5 × 10−6 M) induced multiple shoot formation on all stem explants. Roots were induced on shoots when recultured on nutrient medium supplemented with auxins such as naphthalene‐acetic acid (NAA) or indoleacetic acid (1AA) or when planted in vermiculite. Complete plant formation was obtained when NAA (2 × 1−6, 5 × 10−6 and 10−5 M) was employed in conjunction with BA at 5 × 10−6M. At higher concentrations (10−5M) NAA retards the shoot development while 1AA suppresses it totally. Lower levels of auxins along with the cytokinin did not retard or inhibit shoot differentiation.
Factors Affecting the Sexual Reproduction of a Dermatophyte, Arthroderma benhamiae, in Synthetic Media
Authors: DAVIDSSON MAJVOR , UNESTAM TORGNY
Published: April 2006

Sexual reproduction of many dermatophytes is easily induced in complex media such as soil plus keratin. In Arthroderma benhamiae this process could be initiated also in synthetic agar media. A number of carbon sources (glucose, fructose, galactose, mannose, maltose, lactose, sorbose, sucrose) had about the same stimulatory effect on reproduction, while xylose was inhibitory. Organic sulphur was not crucial for the process in contrast to the nitrogen supply. The nitrogen sources could be divided into four groups; I. very stimulatory (arginine, citrulline, isoleucine, leucine, ornithine, phenylalanine, proline, valine, glutathione); II. stimulatory (alanine, asparagine, lysine, serine); III. slightly stimulatory (aspartic acid, cysteine, glutamic acid, glycine, histidine, urea, NH4Cl, NH4‐tartrate); IV. inhibitory (hydroxyproline, methionine, threonine, tryptophan). Synergistic effects were shown between some amino acids. Generally a combination between 5 g/l glucose and 300–400 mg/l nitrogen induced the largest number of cleistothecia, regardless of the nitrogen source used. The level varied between the sources, however. A C/N ratio of about 10 was optimal while a value above 20 gave no cleistothecia. The optimal temperature for the process was 30°C. Sexual reproduction occurred between pH 4.4 and 8.0 (final values). However, at a final pH above 7.2 the number of ascospores/cleistothecium was reduced.
Extracellular Lytic Enzymes of Myxococcus virescens
Authors: HASKÅ GUNO
Published: April 2006

An easy and rapid method for the purification of a bacteriolytic endopeptidase produced by Myxococcus virescens is described. The bacteria were grown in casitone media and the cells were sedimented by centrifugation. About 1.2 g of montmorillonite were added per liter of cell‐free culture solution. The clay was sedimented by centrifugation and the enzyme was then eluted by 0.05 M Na‐phosphate buffer pH 6.0, containing 0.4 M NaCl. The enzyme was diluted with water and chromatographed on carboxymethyl‐cellulose columns.

The purified enzyme liberated free amino groups but no reducing sugars or N‐acetylhexosamines when acting on purified N‐acetylated cell walls of Micrococcus lysodeikticus. Analysis of N‐ and C‐terminal amino acids in the digestion products showed that the enzyme had liberated about 110 nmoles of lysine ε‐amino groups and 60 nmoles of alanine carboxyl groups per mg of cell wall. When it acted on a bisdisaccharide pentapeptide dimer isolated from M. lysodeikticus cell walls, it cleaved about 30% of the alanyl‐lysine linkages. Consequently the enzyme was an alanyl‐lysine endopeptidase. It had no muramyl‐alanine amidase activity.
Effects of Moderate Water Deficit (Stress) on Wheat Seedling Growth and Plastid Pigment Development
Authors: DUYSEN MURRAY E. , FREEMAN THOMAS P.
Published: April 2006

Etiolated 6‐day‐old wheat (Triticum aestivum L. cv. Chris) seedlings were subjected to osmotic stress by an application of polyethylene glycol 12 h prior to the exposure to a continuous 72‐h light period. The water potential of the primary leaf of stressed seedlings was between –9 and –14 bars throughout the light period.

Stress impaired seedling growth, leaf unfolding, and the increase in leaf area. The imposed osmotic stress reduced total chlorophyll accumulation, particularly after 9 h light, suggesting that this is the approximate time period for the depletion of the protochlorophyll(ide) pool and the pool of an essential protochlorophyll(ide) precursor. The chlorophyll a/b ratio of extracts from stressed and non‐stressed plants was the same during the 72‐h greening period. Water deficit stress impaired carotenoid accumulation sooner than the impairment of chlorophyll production suggesting either a smaller carotenoid pool size of precursors or that the metabolic pathway of carotenoid synthesis was more sensitive to stress. Shifts from the usual plastid pigment absorbance maxima were not observed in these studies.
Occurrence of Endogenous Indol‐3yI‐Aspartic Acid in Light and Dark‐Grown Bean Seedlings (Phaseolus vulgaris)
Authors: TILLBERG ELISABETH
Published: April 2006

An acid ether‐soluble, strongly growth‐stimulating substance revealed by the Avena coleoptile straight‐growth test in methanol extracts from bean seedlings (Phaseolus vulgaris L.) was identified as indol‐3yl‐aspartic acid (IAAsp). Points of agreement between synthetic IAAsp and the investigated growth stimulator were indicated by chromatographic behavior, elution volume in gel filtration, mobility in paper electrophoresis, “colour reaction” with DMCA reagent, ability to form indol‐3yl‐acetic acid (IAA) and aspartic acid after hydrolysis and, finally, biological activity in the Avena test. Furthermore, some experiments demonstrated the occurrence of an inhibitor in extracts from light‐grown tissue. This masked the stimulation of IAAsp in the Avena test when the extracts had been chromatographed in isopropanol: NH3:H2 O. A comparison of the levels of IAAsp between green and etiolated tissue did not reveal any distinct difference, demonstrating that the IAA conjugate IAAsp does not participate in the regulation of the photomorphogenesis.
Regulation of Leaflet Photosynthesis by Developing Fruit in the Pea
Authors: FLINN A. M.
Published: April 2006

Changes in the net photosynthesis of leaflets of Pisum sativum L. (cv. Onward) were found to reflect closely the pattern of assimilate demand in subtended fruit during development. An early peak in leaflet photosynthesis corresponded with the rapid elongation of the fruit; a second peak with the inflation of the pod and initiation of seed growth. However, where the subtended fruit was removed at anthesis, the pattern of fluctuation in leaflet photosynthesis was altered, while leaflets at vegetative nodes maintained a lower photosynthetic rate which fluctuated little. The pattern of net photosynthesis in the fruit appears to reflect the high respiration rates associated with pod elongation and seed growth. This closely coupled system, where fruit assimilate demand modulates the photosynthesis of adjacent leaflets, provides a scope for study of source‐sink relationships with the minimum of experimental manipulation.
Studies on the Nitrogen Metabolism in Ectomycorrhizae
Authors: KRUPA SAGAR , BRÄNSTRÖM GUNNAR
Published: April 2006

Concentrations of free and bound amino acids were determined in 1) the mycorrhizal fungus Boletus variegatus Fr. 2) nonmycorrhizal root systems of aseptically grown Pinus sylvestris L. seedlings, and 3) mycorrhizal root systems of seedlings developed aseptically using the two symbionts.

Arginine (total) was the major amino acid constituent in the mycelium of B. variegatus (18%–22%) during the exponential phase of growth. While 59%–86% of the available arginine was bound during the acceleration phase of growth, in the logarithmic phase 63%–75% was in the free pool. There were differences in the proportions between the individual amino acids in the bound fraction at different stages of growth suggesting production of diverse proteins.

Twenty per cent of the amino acid content of uninfected P. sylvestris root systems was arginine. Infection of the root systems by the fungal symbiont did not result in an increase but a slight decrease in the free arginine content of the composite structure. Almost all other amino acids in the free pool were found in higher concentrations in the mycorrhizal root system. It is suggested that arginine synthesis in B. variegatus is repressed by the arginine available in the host. The mycorrhizal fungus possibly metabolizes the host arginine pool ultimately resulting in more efficient protein synthesis in both the partners.
Effect of Potassium on Proline Accumulation in Maize during Wilting
Authors: MUKHERJEE ILABANTA
Published: April 2006

Leaf discs from maize (Zea mays) grown at high as well as low level of potassium, were treated with different concentrations of KC1 for 2 h in light before exposing to wilting conditions. An enhanced accumulation of free proline effected by wilting was observed in potassium treated discs. Although proline accumulation was much less in leaf discs exposed to short‐term severe wilting conditions than in those exposed to long‐term mild wilting conditions, the effect of potassium was still evident. Under long‐term mild wilting conditions, the enhanced effect was greater in leaf discs from plants grown at high level of potassium than in those from plants grown at low levels of potassium. Treatment with NaCl instead of KC1 did not lead to extra accumulation of proline.
Rhamnose Bound Indole‐3‐Acetic Acid in the Floral Parts of Peltophorum ferrugineum
Authors: GANGULY T. , GANGULY S. N. , SIRCAR P. K. , SIRCAR S. M.
Published: April 2006

The presence of rhamnose bound indole‐3‐acetic acid (IAA) was reported from acetone extract of anthers and carpels of the flowers of Peltophorum ferrugineum. Hydrolysis of the sugar ester gave IAA and rhamnose. Identification of IAA was based on physical measurements supported by bioassay. Bound and free IAA were not detected in petals, seeds and seed coats.
Nutrient Requirements of Vigna sinensis Callus Cultures
Authors: REDDY K. B. S. MURTHY , NARAYANA R.
Published: April 2006

Nutrient requirements of callus tissues previously obtained from Vigna sinensis hypocotyl segments were investigated on modified White's (Miller and Skoog) and Murashige and Skoog's media containing 1 mg/1 of each of 2,4‐D and kinetin, 2% sucrose and 1% agar. Yields of tissues on the latter medium were 3 times more than the former. After studying various organic and inorganic nutrients, two synthetic media have been developed for callus cultures. The above modified White's medium further supplemented with 2% sucrose, and 500 mg/1 of urea or asparagine was suitable for a compact callus with a dry‐to‐fresh‐weight ratio around 8% and on this the tissues grew 15‐ to 17‐fold in 5 weeks. Similarly the Murashige and Skoog's medium further enriched with 2% sucrose, 400 mg/1 of urea or a mixture of aspartic acid (750 mg/1), glutamic acid (250 mg/1), asparagine (250 mg/1) and arginine (250 mg/1), was apt for a friable callus with a dry to fresh weight ratio of 3 to 4% and it promoted a 45‐ to 50‐fold increase in growth in 5 weeks.
Supraoptimal Temperature Effects upon Agrostis palustris
Authors: DUFF D. THOMAS , BEARD JAMES B.
Published: April 2006

Agrostis palustris sods were grown sequentially in a controlled environment chamber at 20–10, 25–15, 30–20, 35–25, and 40–30°C day‐night temperature regimes. Leaves grown at 40–30°C contained 53% more ethanol soluble and 51% more water soluble carbohydrate than those grown at the 4 lower temperature regimes. The increase in ethanol and water soluble carbohydrate in leaves at 40–30°C could not be attributed to a blockage in translocation of photoassimilate to lower plants parts based on quantitative carbohydrate analyses on stem and stolon tissue.

Manometric measurements of photosynthesis indicated that leaf blades grown at the five temperature regimes exhibited different rate capabilities when tested under non‐limiting light and carbon dioxide levels. Oxygen evolution increased directly with temperature from 20 to 40°C and was 8 to 11 fold greater than the rate of carbon dioxide evolution. Both quantitative and qualitative differences in the photosynthetic rate were postulated in the leaf blade tissue tested. The quantitative difference was attributed to a possible difference in the number of cells per unit area and their size. The qualitative difference was attributed to greater thermal stability of leaf proteins when plants were grown at supraoptimal temperatures.

Manometric respiratory rate studies did not indicate similar differences in temperature response in leaf blade tissue grown at the five temperature regimes. The cause of decreased shoot growth at supraoptimal temperatures could not be attributed to decreased and limiting C‐6 carbohydrate synthesis.
Growth and Morphogenesis in Tissue Cultures of Anagallis arvensis
Authors: BAJAJ Y. P. S. , MÄDER M.
Published: April 2006

Morphogenesis has been induced in excised organs and callus tissue cultures obtained from various parts of the seedling and mature plants of pimpernel (Anagallis arvensis). Vigorously growing cell cultures capable of being periodically subcultured have been established in liquid as well as on the agar‐solidified Murashige and Skoog's medium supplemented with 2,4‐D (0.1 mg/1) + kinetin (0.1 mg/l) + coconut milk (10%). The callus tissue obtained from excised hypocotyl segments is white, soft, friable and fast growing, and has been subcultured over a period of two years without showing any sign of decline in growth. The optimum conditions for growth are at pH 5.9, temperature 27°C, and with 4% sucrose as the carbon source. Under appropriate nutritional supply these cultures can be manipulated to induce rhizogenesis in the suspension cultures, and buds and “embryo‐like” structures on agar‐solidified media.

The excised leaves, hypocotyl and stem segments regenerate buds. Of the cytokinins used, 6‐(y,y‐dimethylallylamino)‐purine proved to be the best for the number of cultures producing buds, as well as for the number of buds per culture. Anatomical studies revealed that buds arise from the epidermal and subepidermal layers of leaves and hypocotyl; these buds form shoots which eventually develop into plantlets.
The Influence of NAA, BA and Temperature on Shoot and Root Development from Begonia×cheimantha Petiole Segments Grown in vitro
Authors: FONNESBECH MOGENS
Published: April 2006

The effect of exogenously supplied NAA and BA on the shoot and root formation in isolated petiole segments of Begonia×cheimantha was determined in vitro on a modified White medium at a constant temperature of 24°C. The best development of normally appearing plants was obtained on media containing 0.01 mg × 1−1 of NAA and 0.5 to 1.0 mg × 1−1 of BA. Lower concentrations of BA yielded no shoots, higher concentrations promoted shoot formation, but the shoots were abnormal with malformed leaves. Lower concentrations of NAA resulted in poorer survival rate and no roots, with higher concentrations of NAA many roots developed, but these were thickened and their longitudinal growth inhibited. Temperature proved to be of utmost importance for the induction of shoot formation. Thus significantly fewer shoots were formed at the higher temperature (25°C) than at lower temperatures (15 to 20°C). Temperature immediately after initial transfer was of greatest importance: 25°C, during the first week followed by low temperature, produced very few shoots.
Interrelationship of Abscisic Acid and Gibberellic Acid in the Promotion of Callus Formation in the Abscission Zone of Citrus Bud Cultures
Authors: ALTMAN ARIE , GOREN RAPHAEL
Published: April 2006

The mechanism of ABA‐induced callus formation was studied in sterile bud cultures of Citrus [Citrus sinensis (L.) Osbeck] on defined media. ABA was found to promote callus formation in the abscission zone between the petiole and the branch while inhibiting bud growth. The promoting effect of ABA was dependent on the physiological state of the shoot from which buds were excised, and on the size of the explant. Callus formation was highest in autumn and summer (i.e. younger) buds, and lowest in older buds excised from previous summer flush.

GA was only slightly active in promoting callus formation when applied separately, but showed a highly synergistic effect when applied with ABA: maximal callus formation was attained at a combination of 10−5M ABA and 10−6 MGA in the medium. Subcultures of ABA‐induced callus revealed that ABA inhibited the growth of isolated subcultured callus, while IAA and kinetin, and especially GA, promoted its rapid proliferation. A general decrease in protein synthesis was found in the abscission zone during the first 5 days of induction, while total protein content changed only slightly.

The results suggest that ABA‐induced callus formation in Citrus bud explants is a multiphasic phenomenon involving, at least, two stages: (1) activation of certain cells in the abscission zone by ABA, resulting in the formation of callus layers, and (2) subsequent proliferation of the callus tissue, which is dependent on the hormonal balance in the explant. This growth‐promoting effect of ABA seems to be a general phenomenon in explants exposing a cut‐surface.
Regulators of Cell Division in Plant Tissues
Authors: LETHAM D. S.
Published: April 2006

Procedures were devised for purification of the cytokinins in the milk of mature coconuts (Cocos nucifera fruits). One cytokinin isolated in crystalline form was unequivocally identified as 9‐β‐D‐ribofuranosylzeatin. This compound appeared to account for a large proportion of the cytokinin activity in n‐butanol extracts of coconut milk. The activity which was not extracted by n‐butanol was largely due to unidentified compounds which could be partially purified by adsorption onto and elution from charcoal.
Translocation and Complex Formation of Picloram and 2,4‐D in Rape and Sunflower
Authors: HALLMÉN ULF
Published: April 2006

Uptake, translocation and complex formation of 14C‐labelled 4‐amino‐3,5,6‐trichloropicolinic acid (picloram) and 2,4‐dichlorophenoxyacetic acid (2,4‐D) in seedlings of rape (Brassica napus L. cv. Nilla) and sunflower (Helianthus annuus L. var. uniflorus) were studied. Sunflower is susceptible both to 2,4‐D and picloram, while rape is susceptible to 2,4‐D but more tolerant to picloram. The uptake of the herbicides through the leaves was almost complete in both species. Translocation of 2,4‐D into the roots took place more readily than that of picloram. In sunflower about 50 per cent of the applied 2,4‐D was extruded through the roots into the nutrient solution after 9 days. In the picloram‐treated sunflower most of the activity was found in the aerial parts, while in picloram‐treated rape most of the activity still occurred in the treated leaf after 9 days. No activity at all was found in the roots or in the nutrient solution of the picloram‐treated rape seedlings.

While the major part of 2,4‐D always was found in the state of free herbicide, a large fraction of picloram was rapidly bound into water‐soluble complexes. This binding was especially pronounced in rape. Separation by paper chromatography showed that different radioactive compounds were formed. Most of these could be hydrolyzed, thereby releasing free herbicide.

The results support the hypotheses that complex formation could counteract herbicide translocation and toxicity of auxin herbicides.
Root Formation in Pea Cuttings
Authors: MOHAMMED SHAFAAT , ERIKSEN E. NYMANN
Published: April 2006

Auxin was applied to the upper part of the cuttings, which were both decapitated and disbudded on the same day. The applied auxin was removed by redecapitating the cuttings at different time intervals. In a second experiment, auxin was applied either to the upper or lower part of the decapitated and disbudded cuttings at different time intervals.

In cuttings, which were redecapitated after 1 and 2 days, the root formation was reduced considerably. The redecapitation after 3 days had no adverse effect on the root formation. Cuttings treated with auxin at different time intervals showed a weaker root promotion on days 0 and 1 than on the subsequent days.

The results emphasize the fact that auxin is active only during the first part of the root initiation phase. A continuous flow of auxin for a period of the first 3 days during the root initiation is of overriding importance. There appears to be at least two different stages of the root initiation phase, (ia) auxin active stage, and (ib) auxin inactive stage. The results also seem to indicate that some other factors, in addition to auxin, are active during the first stage of the root initiation phase.
Kinetic Studies of a (Na++ K++ Mg2+) ATPase in Sugar Beet Roots
Authors: LINDBERG SYLVIA , HANSSON GUNNAR , KYLIN ANDERS
Published: April 2006

Kinetic studies of a microsomal, dithiotreitol treated, homogenate from sugar beet roots led to the following conclusions about its ATPase activity: (1) MgATP in complex appears to be the primary substrate for the reaction. The reciprocal equilibrium constant for the binding to the enzyme is estimated to be approximately 0.2 × 10−3M. (2) Free ATP acts as a competitive inhibitor of the MgATP. The binding constant is about twice as high as for MgATP. Consequently the enzyme has less affinity for ATP than for MgATP. (3) Free Mg2+ has little influence on the velocity, as the binding affinity of the enzyme for Mg2+ is almost negligible.
DNA Synthesis, Mitosis and Ploidy of Dividing Cells in Early Crown Gall
Authors: KUPILA‐AHVENNIEMI SIRKKA , THERMAN EEVA
Published: April 2006

DNA synthesis, mitosis and ploidy of dividing cells were studied during 30 h after wounding around wounds inoculated with Agrobacterium tumefaciens, around sterile wounds and in control stems of Vicia faba. DNA synthesis was examined by counting nuclei labelled with 3H‐thymidine in slides in which mitoses had been counted and analyzed before autoradiography.

The main results were that around inoculated wounds, DNA synthesis and the number of mitoses showed a peak between 12 and 22.5 h. Both types of wounding induced mitoses, many of them polyploid (DNA content higher than 4C), both in the pith and the cortex, whereas in the control stems only diploid mitoses, mostly in the stelar area, were seen. The first polyploid (8C) mitoses around the inoculated wounds took place at 12 h and at 15.5 h 32C mitoses were seen; around the sterile wounds the first 8C divisions occurred at 26 h. The frequency of polyploid mitoses and their degree of ploidy continued to be considerably higher around the crown gall than around the control wounds. When a cell with a higher than 4C content is induced to divide, the 12 chromosomes, as a rule, consist of four, eight, 16 or 32 chromatids, instead of the normal two.

The early division of highly polyploid cells around the inoculated wounds is obviously caused by growth factors which are known to be produced by the bacteria. It appears possible that this ability to synthesize excessive amounts of growth factors is subsequently transferred to the host cells through bacterial DNA.
On the Metabolism of Tortula ruralis Following Desiccation and Freezing: Respiration and Carbohydrate Oxidation
Authors: BEWLEY J. DEREK , THORPE TREVOR A.
Published: April 2006

Recovery from desiccation by Tortula ruralis (Hedw.) Gaertn., Meyer and Scherb was accompanied by an immediate, rapid increase in respiration (measured as oxygen uptake) at 25.5°C or 3.5°C. The respiratory burst was greater on rehydration of moss which had been rapidly desiccated over silica gel than that which had been more slowly desiccated in atmospheres of high relative humidity. No respiration was observed in dry moss. Dried moss which had been placed in liquid nitrogen resumed respiration on rewarming and rehydration but moss which had been frozen in the hydrated state respired to a lesser extent and showed signs of freeze damage. In the initial stages of slow drying a slight increase in respiration was noted, followed by a gradual decrease as drought became more severe.

In contrast to observations made on many higher plants under drought stress, this moss did not exhibit any changes in its starch and sugar content during or following desiccation, nor were there any changes in free proline levels. Using (1‐14C)‐glucose and (6‐14C)‐glucose, the relative activities of the Embden–Meyerhof–Parnas and pentose phosphate pathways in hydrated and rehydrated moss were determined, as were the activities of specific enzymes involved in these pathways. An increased activity of the Embden–Meyerhof–Parnas pathway of glucose oxidation on rehydration of Tortula was observed. The possible significance of this latter observation is outlined.
Hormone‐Induced Reversal of Color Change and Related Respiratory Effects in Ripening Apricot Fruits
Authors: ABDEL‐GAWAD HESHAM , ROMANI ROGER J.
Published: April 2006

Preharvest applications of N6‐benzyladenine and gibberellic acid caused a lowering of respiratory rates and a transient reversal in the color changes normally associated with the postharvest ripening of apricot fruits (Prunus armeniaca L.) Light transmission at 589 and 657 nm were used to detect color change. A physiological and metabolic link is implied by the close temporal coincidence of both the reversal in color change and the reversal in respiratory rate that occurs at the climacteric minimum. Postharvest treatments with the same phytohormones had generally similar but much less pronounced effects.
Root Formation of Pea Cuttings in Relation to the Irradiance of the Stock Plants
Authors: HANSEN JÜRGEN , ERIKSEN ERIK NYMANN
Published: April 2006

Pea plants were grown at different irradiances for eleven days. At this stage they were used for cuttings. The irradiance during the rooting period (155 mW · dm−2) was the same in all the experiments, Cuttings from stock plants cultivated at the weakest irradiance obtained the highest number of roots, and the poorest rooting appeared in cuttings from stock plants grown at the highest irradiance. The results indicate that the nutritional status of the stock plant is an important factor for root formation in the cutting. Light may influence the production of inhibitors which directly or indirectly affect root formation. The possible role of carbohydrates and growth promoters in the process of root formation is discussed.
Proline‐Dehydrogenase from Pumpkin (Cucurbita moschata) Cotyledons
Authors: RENA ALEMAR B. , SPLITTSTOESSER WALTER E.
Published: April 2006

A NAD specific proline‐dehydrogenase was found in pumpkin (Cucurbita moschata Poir. cv. Dickinson Field) which oxidized proline to Δ1‐pyrroline‐5‐carboxylate. NADP did not substitute for NAD and L‐proline‐methyl‐ester and thiazolidine‐4‐carboxylate were substrates in the reaction, at a rate of 107% and 33% respectively, of the rate with L‐proline. Pumpkin cotyledons contained the bulk of the enzyme activity with 90% of the activity being in the soluble fraction. Proline‐dehydrogenase, which was not treated at high temperature, was stable at –10°C for 4 months in the presence of high ammonium sulfate concentration. The Michaelis constant for NAD was 2.2 mM and for L‐proline was 2.5 mM. At 5 mM NADP, a 40% non‐competitive inhibition of proline‐dehydrogenase was obtained, while 50 μM NADP was sufficient to induce 20% inhibition.
Effect of Age on Adenosine Triphosphatase Activity from Tobacco Chloroplasts
Authors: SCHERINGS G. , KUIPER P. J. C.
Published: April 2006

Adenosine triphosphatase activity of tobacco leaf chloroplasts in the dark was measured, using leaves of different age as determined by the position of the leaves along the stem. The activity of the chloroplast preparations strongly decreased with age, regardless of the addition of Mg2+ or Ca2+. Opposite effects of Mg2+ and Ca2+ on the activity of the chloroplasts were noted in experiments where different ratios of Mg2+/Ca2+ were applied. They were related to the age of the leaves, Ca2+ strongly stimulated the activity of the preparations from old leaves but was practically without effect in young, just expanded leaves. Mg2+ slightly stimulated the activity from old leaves while it invariably inhibited the hydrolytic activity of preparations from young leaves.
Effect of (2‐Chloroethyl)phosphonic Acid on Flower Induction in Juvenile Mango (Mangifera indica) Seedlings
Authors: CHACKO E. K. , KOHLI R. R. , SWAMY R. DORE , RANDHAWA G. S.
Published: April 2006

Spray applications of 1000 mg/l (2‐chloroethyl)phosphonic acid (CEPA) five times, at weekly intervals, during November and early December induced heavy flowering in ringed and nonringed juvenile mango seedlings. The treated plants produced flower buds which opened by the end of December, while the control and ringed seedlings produced only a new flush of vegetative growth. The results show that CEPA could be profitably used for early evaluation of hybrid seedlings in mango breeding programme.
Partitioning of Cytokinins between Ethyl Acetate and Acid Water Phases
Authors: HEMBERG TORSTEN
Published: April 2006

Model‐experiments to determine the quantitative yield in purification of cytokinin extracts have been performed with kinetin, isopentenyladenine and zeatin and with their ribosides. When these substances in water solution of pH 3 are shaken three times with equal volumes of ethyl acetate, most of the kinetin and isopentenyladenine and their ribosides go over to the ethyl acetate phases. Zeatin and its riboside stay in the water phase. The unsuitability of using ethyl acetate to purify cytokinin extracts is pointed out.
Control of Aromatic Amino Acid Biosynthesis in Cultured Plant Tissues: Effect of Intermediates and Aromatic Amino Acids on Free Levels
Authors: WIDHOLM J. M.
Published: April 2006

Shikimate, anthranilate, indole, l‐tryptophan, phenylpyruvate, l‐p henylalanine, p‐hydroxyphenylpyruvate or l‐tyrosine were added to suspension‐cultured Nicotiana tabacum (tabacco) and Daucus carota (carrot) tissues and incubated for 24 hours. Uptake of each compound was substantial as measured by its decrease in the medium.

The levels of free tryptophan, phenylalanine and tyrosine were determined in the tissues after the 24 hours incubation. Shikimate did not change the aromatic animo acid levels in carrot tissue, but did increase all three in tobacco (3‐fold or more), indicating a less stringent feedback control in tobacco.

Anthranilate and indole increased the tissue tryptophan levels in both species by at least 17‐fold, showing that the flow from anthranilate and indole to tryptophan was apparently unhindered by enzymatic control mechanisms.

When tryptophan levels were elevated in both carrot and tobaccotissues by anthranilate, indole or tryptophan addition, there was also an increase in free phyenylalanine and tyrosine. This might be due to the reversal of phenylalanine and tyrosine feedback inhibition of chorismate mutase by the high tryptophan in the tissue. Chorismate mutase activity in tobacco crude extracts could be inhibited by 66–90% by 1 mM phenylalanine and /or tyrosine. Tryptophan at 1 mM stimulated the enzyme activity by 1/3 and completely reversed the phenylalanine and/or tyrosine inhibition of enzyme activity. Chorsimate mutase activity amino acids under a variety of conditions.

Phenylpyruvate increased the phenylalanine levels and p‐hydroxyphenylpyruvate increased the tyrosine levels in carrot and tobacco tissues indicating that there was no feedback control of the last step in phenylalanine and tyrosine biosynthesis.
Effects of Four Temperature Regimens on the Gibberellin Content of Winter Wheat cv. Kharkov
Authors: REID D. M. , PHARIS R. P. , ROBERTS D. W. A.
Published: April 2006

Kharkov 22 M.C. winter wheat was grown continuously from seed under four temperature regimens; 2°C; 2°C then transferred to 20°C; 6°C, and 20°C. Plants were harvested at the 4‐leaf stage (except the 2°C plants which were harvested at the 3‐leaf stage) and the levels of endogenous gibberellins (GAs) were measured and their cold hardiness determined. The GA content of 20°C and the 6°C seedlings were about equal and greater (by 4‐ to 30‐fold) than the GA content of 2°C seedlings that had been transferred to 20°C (i.e. vernalized). The GA content of the 2°C seedlings was least of all, being 28‐ to 320‐fold less than the 20°C seedlings. At harvest the leaves of the 20°C seedlings were somewhat larger than those of the seedlings grown at 2°C and transferred to 20°C. The leaves of the 6°C seedlings were very much smaller and the leaves of the 2°C seedlings were smallest of all.

It is concluded that while GAs may play a role in controlling leaf size and level of cold hardiness of wheat, they are not the most important factor.
Growth Chamber Illumination and Photomorphogenetic Efficacy I. Physiological action of infrared radiation beyond 750 nm
Authors: DEUTCH BENTE , RASMUSSEN OLE
Published: April 2006

Plants cultivated in growth chambers under such artificial illumination as fluorescent tubes show certain characteristic differences from plants grown in nature or under incandescent lamps. The plants grown under fluorescent light are shorter and more darkly pigmented; they also show different daylength requirements for certain photoperiodic responses. It was assumed that these effects were caused by the relative deficiency of far red irradiation (λ= 700–750 nm) in the emission from the fluorescent lamps. This assumption was tested on such light sensitive phenomena as stem elongation, flowering, the formation of resting organs, chlorophyll synthesis, and production yield in several plant genera. In all cases the plants were grown under long days (16 h). Six common types of growth chamber illumination were tested for their efficacy for long‐day induction. The spectral energy distribution of the lamps was measured. The emission from the various lamp types showed only small differences within the region of visible light (λ: 400–750 nm), but much larger diversity in the ratio of visible to infrared radiation (λ: 750–1000 nm). A strong correlation exists between the relative emission of infrared radiation and the photomorphogenetic efficacy of the lamps. Under fluorescent light the long‐day effect was weak or missing, but increased with increasing infrared emission. High infrared emission was also favourable for high production yield.