bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium and potassium relations of Spergularia marina following N and P deprivation: results of short‐term growth studies
Authors: Wickens Linda K. , Cheeseman John M. 
Published: May 2006

In this, we consider the coordination of plant growth and ion acquisition, reporting the short‐term adjustments of growth and K+ and Na+ relations which follow when plants are subject to a sudden deprivation of N and P. The plant used for the experiments, Spergularia marina (L.) Grieseb., is a small coastal halophyte, and the growth medium was 0.2 × modified seawater. By considering nutrients whose availability has not been changed, we report on an aspect of organismal integration which has received little attention either experimentally or in mathematical models. The studies are limited to the first 60 h after N and P deprivation in order to consider changes that, if they are not primary responses, are not temporally remote, passive adjustments.For growth analyses, plants were used approximately 30 days after germination and 16 days after transfer to solution culture. Random harvests were made at hourly invervals, and after 12 h, one‐half of the plants were transferred to cultures without N or P. Tissue analyses were used to calculate relative growth rates, relative accumulation rates and net uptake rates. For comparison, isotope uptake studies using 42K+ and 22Na+ were conducted at 12, 36 and 60 h after deprivation.The effects on growth and biomass allocation were very rapid, detectable within 13 h. K+ transport also responded quickly, and from the beginning of the study, there was essentially no net translocation of K+ to the shoot. Isotope studies confirmed the responsiveness, with translocation reduced 33 and 90% after 12 and 36 h, respectively. Though Na+ adjustments were slower, they were coordinated with growth such that tissue concentrations in the N and P‐deprived plants were comparable to those in the controls. We conclude that N and C are insufficient elements on which to build mathematical models useful to environmental physiologists. At a minimum, the incorporation of K+ relations in growth models would both allow the development of the osmotic potential needed to drive cell expansion, and provide a means to probe –experimentally as well as mathematically – the coordinating mechanisms of plant growth and resource management.
The effects of mineral nutrition and benzyladenine on the plasmalemma ATPase activity from roots of wheat and Plantago major ssp. pleiosperma
Authors: Kuiper Daan , Sommarin Marianne , Kylin Anders 
Published: May 2006

There is an increasing awareness of the possibilities of mineral nutrition as regulator of growth substance action and vice versa. The present paper focuses on the effects of mineral nutrition and benzyladenine at the level of the plasma membrane. Seedlings of wheat (Triticum aestivum L. cv. Drabant) and juvenile plants of Plantago major L. ssp. pleiosperma (Pilger) were grown hydroponically at different mineral levels with or without benzyladenine. Purified plasmalemma preparations from roots of wheat and P. major ssp. pleiosperma were obtained by the two phase partitioning method, using 6.5% (w/w) of each of Dextran T‐500 and polyethylene glycol 3350. The Mg2+ and (Mg2++ K+) dependent ATPase activities of the root plasmalemma in both species and the (Mg2++ Cl−) one in P. major ssp. pleiosperma increased with increasing mineral levels, but the ionic strength did not influence the substrate specificity, the sensitivity to inhibitors or the pH optima.The addition of 10−8M benzyladenine to a nutrient solution increased the ATPase activities. The pH optima and the sensitivity to several inhibitors were not affected by benzyladenine, but the substrate specificity for ATP decreased, except for the K+ stimulation. In conclusion, benzyladenine mimics the effects of a higher mineral level than actually applied. Data from this and previous experiments indicate that benzyladenine exerts its effects by increasing the endogenous cytokinin concentrations and by modulating membrane components.
Photoinhibition and recovery of photosynthesis in intact barley leaves at 5 and 20°C
Authors: Greer D. H. , Ottander C. , Öqust G. 
Published: May 2006

Photoinhibition of photosynthesis and its recovery were studied in intact barley (Hordeum vuigare L. cv. Gunilla) leaves grown in a controlled environment by exposing them to two temperatures, 5 and 20°C, and a range of photon flux densities in excess of that during growth. Additionally, photoinhibtion was examined in the presence of chloramphenicol (CAP, an inhibitor of chloroplast protein synthesis) and of 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU). Susceptibility to photoinhibition was much higher at 5 than at 20°C. Furthermore, at 20°C. CAP exacerbated photoinhibition strongly, whereas CAP had little additional effect (10%) at 5°C. These results support the model that net photoinhibition is the difference between the inactivation and repair of photosystem II (PSII); i.e. the degradation and synthesis of the reaction centre protein, Dl. Furthermore, the steady‐state extent of photoinhibition was strongly dependent on temperature and the results indicated this was manifested through the effects of temperature on the repair process of PSII. We propose that the continuous repair of PS II at 20°C conferred at least some protection from photoinhibition. At 5°C the repair process was largely inhibited, with increased photoinhibition as a consequence. However, we suggest where repair is inhibited by low temperature, some protection is alternatively conferred by the photoinhibited reaction centres. Providing they are not degraded, such centres could still dissipate excitation energy non‐radiatively, thereby conferring protection of remaining photochemically active centres under steady‐state conditions.A fraction of PS II centres were capable of resisting photoinhibition when the repair process was inhibited by CAP. This is discussed in relation to PS II heterogeneity. Furthermore, the repair process was not apparently activated within 3 h when barley leaves were transferred to photoinhibitory light conditions at 20°C.
Flowering responses to light‐breaks in photomorphogenic mutants of Arabidopsis thaliana, a long‐day plant
Authors: Goto Nobuharu , Kumagai Tadashi , Koornneef Maarten 
Published: May 2006

Flowering response and plant form of photomorphogenic mutants (hy1, hy2, hy3, hy4 and hy5) of Arabidopsis thaliana (L.), a long‐day plant, were examined in long and short days. There were only slight differences among genotypes including Landsberg wild type with respect to the flowering time under long days. The effect of 1 h light‐(night)‐breaks of far‐red, red, blue and white light given in the middle of the dark period of plants grown under short days, was studied. Effects of far‐red light applied at the end or the beginning of the main photoperiod on flowering and plant form were also examined. The light‐breaks with all the above mentioned light qualities promoted floral initiation of all the genotypes including the wild type in terms of both the flowering time and the number of rosette leaves. In general, far‐red light was most effective. It is possible to classify the hy‐mutants into 3 groups by their responses to light‐breaks under short day conditions: (a) Mutants hy2 and hy3, which have a reduced number of rosette leaves, and flower early. Red light is as effective as far‐red light. The wavelength of light‐breaks is relatively unimportant for flowering response. (b) Mutants hy4, hy5 and Landsberg wild type, which have a greater number of rosette leaves, and flower relatively late. The effectiveness of light‐breaks is in the following order, far‐red, blue, and red light, which is in reverse order to the transformation of phytochrome to the Pfr form. (c) Mutant hy1, which behaves anomalously with respect to relations between flowering time and number of rosette leaves; late flowering with reduced number of rosette leaves. Red, blue and far‐red light are effective, but white light is ineffective for reducing the number of rosette leaves.When far‐red light was given in the middle of the night or at the end of the main photoperiod, it markedly reduced the number of rosette leaves compared to those grown under short days for all the genotypes, while when applied at the beginning of the main photoperiod far‐red light did not affect the number of rosette leaves. Different effects on the plant form dependent on the time of treatment with far‐red light‐breaks are also discussed.
Stability of salt tolerance at the cell level after regeneration of plants from a salt tolerant tobacco cell line
Authors: Watad A. A. , Swartzberg D. , Bressan R. A. , Izhar S. , Hasegawa P. M. 
Published: May 2006

Plants were regenerated from both the wild type and a stable NaCI‐tolerant line of tobacco cells (Nicotiana tabacum/gossii). The regeneration process was much more difficult in the case of the NaCI‐tolerant line and was only successful in the absence of NaCI. These plants differed morphologically from those regenerated from the wild type cell line, exhibiting abnormally short internodes, small leaves and reduced growth. Cell suspension cultures derived from plants regenerated from the stable NaCI‐tolerant line retained a high level of tolerance to salt. The NaCI‐concentration required to reduce fresh and dry weight gain by 50% was about twice that observed in the case of the cells obtained from wild type plants.The results presented here, together with those of Watad et al. (1985), indicate that resistance to salt is operating and stable at the cellular level before and after plant regeneration. When the regenerated plants were grown in increasing levels of salt their growth response was not clearly different from that of the plants regenerated from the wild type cell line. However, the survival of plants on high concentrations of NaCI tended to be higher in the case of plants regenerated from the NaCI‐tolerant cell line.
Phytohormonal changes in greening and senescing intact cotyledons of oilseed rape and pumpkin: influence of the growth retardant BAS 111 ˙˙ W
Authors: Grossmann Klaus , Kwiatkowski Jacek , Häuser Christiane 
Published: May 2006

The triazole growth retardant BAS 111‥W delayed senescence in cotyledons of pumpkin (Cucurbita maxima L. cv. Gelbe genetzte Riesenmelone) and stimulated chlorophyll synthesis in greening cotyledons of oilseed rape (Brassica napus L. cv. Petranova) seedlings. In both cases, changes of phytohormone‐like substances in the cotyledons were analyzed on a fresh weight basis by immunoassay.After soil treatment with increasing retardant concentrations, a close correlation was observed in senescing cotyledons of pumpkin between a reduced loss in total chlorophyll and increasing levels of dihydrozeatin riboside (DZR) and trans‐zeatin riboside (ZR)‐type cytokinins. In contrast, the levels of isopentenyladenosine (IPA)‐type cytokinins, 3‐indoleacetic acid (IAA) and gibberellin (GA) did not change significantly. The levels of abscisic acid (ABA) were slightly elevated at low retardant concentrations but dropped considerably below those of controls at higher doses. Consequently, the molar ratio of total cytokinin to ABA content changed from approximately 1:40 in controls (50% of initial chlorophyll) to 1:3 in cotyledons treated with 3 mg BAS 111‥W plant−1 (85% of initial chlorophyll). These changes, together with the known reduction of ethylene production by plants treated with nitrogen‐heterocyclic retardants, can explain the delayed senescence in pumpkin cotyledons. Likewise, when etiolated, BAS 111‥W‐treated seedlings of oilseed rape were exposed to light, the stimulation of chlorophyll synthesis in the cotyledons was accompanied by an accumulation of DZR‐ and, particularly, ZR‐type cytokinins and IAA. In contrast, GA and ABA contents decreased slightly. We conclude that the influence of BAS 111‥W on cytokinin levels might be involved in the stimulation of greening.
Phosphatidylcholine biosynthesis in celery cell suspension cultures with altered sterol compositions
Authors: Rolph Carole E. , Goad L. John 
Published: May 2006

Cell suspension cultures of celery were treated with the plant growth regulator, paclobutrazol. Lipid analysis revealed that use of this xenobiotic had little effect on the quantity or acyl quality of the major phospholipid classes or on the actual amounts of free sterol present in the cell. It did however, cause dramatic changes in the free sterol profile exhibited by treated cultures. In this respect, an increase in 14α‐methylsterols was observed.The synthesis of phosphatidylcholine in celery cell suspension cultures with altered free sterol compositions was studied using two radiolabelled biosynthetic precursors, [3H‐methyl]choline and [3H‐methyl]methionine. The studies showed that the rate of phosphatidylcholine biosynthesis via the CDP‐base pathway proceeded at a slower rate in paclobutrazol treated cultures. Accumulation of label phosphocholine was observed arising from reduced CTP:cholinephosphatecytidylyltransferase activity. In contrast, phosphatidylcholine biosynthesis via the sequential methylation of ethanolamine derivatives appeared to be enhanced in cells that had an unusually high 14α‐methylsterol content. From these investigations it may be postulated that the biosynthesis of phosphatidylcholine in Apium graveolens suspension cultures may be regulated by membrane sterol composition.
When plant teratomas turn into cancers in the absence of pathogens
Authors: Gaspar Thomas , Hagège Daniel , Kevers Claire , Penel Claude , Crèvecoeur Michèle , Engelmann Isabelle , Greppin Hubert , Foidart Jean‐Michel 
Published: May 2006

Habituated calli have long been classified as neoplasms together with tumors from different origins. The general opinion is that habituation is a reversible process with an epigenetic basis. This is probably true in most cases examined. However, we show here that there might be several degrees of habituation, which can be considered as steps of a neoplastic progression leading to cancerisation in the absence of an introduced oncogenic pathogen. Cell rejuvenation, loss of the capacity to organize meristematic centers, and loss of totipotency are proposed to define plant cancer through this neoplastic progression of a callus.Habituated tissues share many morphological and biochemical similarities with so‐called vitreous shoots from micropropagation. Vitrification and hyperhydric malformations of shoots raised in vitro may be considered as steps of another neoplastic progression, which leads to cancerisation also in the absence of introduced oncogenic pathogens. In this case death of the whole organism occurs either through direct apex necrosis or indirectly, from the loss of the capacity for the primary meristems to function normally, which gives rise to completely anarchic structures. As in the animal kingdom, carcinogenesis in plants is the final result of a multistep process involving the irreversible conversion of a stem cell to a terminal‐differentiation‐resistant cell.
Effects of temperature on the mode of pollen development in anther culture of Brassica campestris
Authors: Hamaoka Yoh , Fujita Yukio , Iwai Sumio 
Published: May 2006

In anther culture of Brassica campestris L., the yield of pollen‐derived embryoids is greatly stimulated by a high‐temperature (35°C) tratment for the first 1 to 3 days of the culture. We have inestigated the effects of the high‐temperature treatment on the mode of pollen division in cultured anthers.Anthers containing late uninucleate pollen were cultured on modified B5 medium. High‐temperature treatment for the first 24 h inhibited the normal development of the pollen and induced abnormal symmetrical division. Which is the first step in androgenesis. This symmetrical division was rarely observed in pollen developed in vivo. In anthers cultured without high‐temperature treatment, the mode of pollen development was similar to that in vivo. This suggests that the normal differentiation of the pollen is blocked by high temperatures, and sporophtic growth is induced. Sucrose (0.29 M) was essential for the induction of this symmetrical division, though neither plant growth regulator nor any other nurient was necessary. Pollen division could not be induced effectively if sucrose was replaced by either mannitol or sorbitol plus a lower concentration of sucrose. Therefore, it seems that sucrose actively influences the embryogenic division of pollen, and does not have only an osmotic effect.
Leaf respiration in Piper species native to a Mexican rainforest
Authors: Fredeen Arthur L. , Field Christopher B. 
Published: May 2006

We measured leaf respiration with a Clark‐type oxygen‐electrode in 6 species of the genus Piper (Piperaceae) growing naturally in wet evergreen rainforest, in microsites characterized by a broad range of light availabilities. Species normally found in large gaps and clearings (Piper auritum and P. umbellatum) had approximately twice the dark respiration per unit of leaf area or dry mass as species found predominantly in shaded understory sites (P. aequale, P. lapathifolium and P. amalago). within a species, dark respiration was lower in the individuals growing in low‐light sites than in the individuals growing in high‐light sites. Over all species, leaf respiration was positively correlated with the average daily photosynthetically active photon flux density (PFD) at each site, and negatively correlated with mean leaf longevity. Respiration was insensitive to leaf age in a shade species. (P. lapathifolium) and in a generalist (P. hispidum) but decreased with increasing leaf age in a gap specialist (P. aurtium).In experiments on greenhouse‐grown plants, we titrated respiration with potassium cyanide (KCN) and/or salicylhydroxamic acid (SHAM) to determine the cytochrome and alternative pathway components to respiration in 4 Piper species. All 4 species, representing gap, generalist and shade species, exhibited alternative pathway respiration. Engagement of the cytochrome pathway (ϱcyt) varied from 0.69 in P. auritum to 1.04 in P. lapathifolium and engagement of the alternative pathway (ϱalt varied from 0.41 to 1.02. Although the shade species had lower respiration rates than the gap species, the capacities for cytochrome and alternative pathway respiration made up similar or greater fractions of total respiration in shade species.
Effects of anaerobiosis on ethylene production, respiration and flowering in iris bulbs
Authors: Marissen N. , Kanneworff W. A. , van der Plas L. H. W. 
Published: May 2006

Ethylene production of iris bulbs (Iris hollandica cv. Ideal) was very low. When stored at 30°C, production was 12–20 pmol C2H4 (kg fresh weight)−1 h−1. Higher temperatures (35°C, 40°C) enhanced the ethylene production; a treatment with 40°C for ca 7 days caused a 3 times higher ethylene production than at 30°.During anaerobic storage (in 100% N2) ethylene production was equal to that of control bulbs. When after a 7 day period of anaerobiosis the N2 was replaced by air, a burstlike ethylene production was observed. Twenty‐four h after the replacement, ethylene production was equal to control values again.The effects of this production of ethylene on mitochondrial respiration and flowering were investigated. When mitochondria were isolated immediately after the anaerobic treatment (before the enhanced ethylene production) alternative pathway capacity was not detectable, a situation also occurring in control bulbs. When mitochondria were isolated 24 h after the end of the anaerobiosis (after the ethylene burst) uninhibited respiration did not change significantly, but a capacity of the alternative pathway was observed. The increase in alternative pathway capacity after anaerobiosis was partly inhibited by 2,5‐norbornadiene (NBD), an ethylene antagonist.Fermentation occurred during anaerobiosis: ethanol concentrations increased during the treatment and decreased when air was supplied. When bulbs were exposed to ethanol vapour the alternative pathway was induced but only when very high ethanol levels in the bulbs were reached. The amount of ethanol accumulated in the bulbs during a 7 day anaerobic treatment was far too low to explain the observed induction of alternative pathway capacity.Flowering percentages were enhanced after a 24 h treatment with ethylene and after a 7 day anaerobic treatment. NBD significantly inhibited the effect of exogenous ethylene and of anaerobiosis on flowering. Ethanol was not able to induce flowering. The burst‐like production of ethylene after anaerobiosis probably is responsible for the effects on respiration and flowering.
Increased resistance to copper‐induced damage of the root cell plasmalemma in copper tolerant Silene cucubalus
Authors: De Vos C. H. R. , Schat H. , De Waal M. A. M. , Vooijs R. , Ernst W. H. O. 
Published: May 2006

The relation between copper tolerance and the sensitivity of plants with respect to the effect of copper on the plasmalemma of root cells was studied using plants from one copper sensitive and two copper tolerant populations of Silene cucubalus Wib. In each population, the external copper concentration needed to induce ion leakage (a measure of damage to the permeability barrier) was similar to the highest no‐effect‐concentration of copper for root growth in that population. At higher concentrations, the degree of root growth inhibition paralleled the rate of ion leakage, the degree of trypan blue staining (a measure of plasmalemma integrity) and the accumulation of lipid peroxidation products. The amount of copper taken up by the plants was inversely related to their level of copper tolerance. Compared to copper sensitive plants, copper tolerant plants showed no increased resistance to either the sulfhydryl reagent N‐ethylmaleimide or the free radical‐producing compound cumene hydroperoxide.These results indicate that damage to the permeability barrier of root cells constitutes the primary effect of copper toxicity in both sensitive and tolerant plants, and that copper tolerance is coupled to the ability of the plants to prevent such damage. This ability might depend on exclusion of copper by the root cell plasmalemma.
Aluminium avoidance by Mucuna pruriens
Authors: Hairiah Kurniatun , van Noordwijk Meine , Stulen Ineke , Kuiper Pieter J. C. 
Published: May 2006

The hypothesis was tested that the avoidance of acid subsoil by the velvet bean Mucuna pruriens is based on a mechanism acting on the whole root system rather than on individual roots. In a split‐root experiment with circulating nutrient solution the growth of plants with Al‐containing (+/+) or Al‐free (0/0) solution on both sides of the root system was compared with that of plants which had a choice (0/+). Two levels of Al (110 and 185 μM) were tested at two levels of Ca (50 and 1250 μM). In the 185 μM Al treatment the concentration of monomeric Al varied between 53 μM, directly after refreshing the solution, and 5 μM at harvest time.An external Al concentration of 110 μM had no effect on shoot and root dry weight, while 185 μM Al applied to both sides of the root system (+/+) increased root dry weight and reduced shoot dry weight and shoot/root ratio, compared with the 0/0 control. Application of 185 μM Al to half of the roots, ied to a significant shift in root growth in favour of the control side; this response is described here as Al avoidance. On the basis of total root length, root dry weight and root surface area, the ratio of 0/+ roots was 3.1, 2.8 and 2.4, respectively.Al avoidance at 185 μM Al was confirmed in another experiment, in which root response was measured to a local P source, supplied in a third compartment containing only KH2PO4. A significant increase in root length and dry weight in this compartment was observed, when other roots of the same plant were growing in the presence of Al. This result indicates that Al avoidance by Mucuna roots is related to P preference.