Nitrate reduction in tendrils of semi-leafless pea

The recessive gene af produces a modification of Pisum sativum L. leaf morphology, where leaflets are replaced by tendrils. Previous reports have suggested that tendrils may contribute to plant growth in a similar way to flat leaf structures, but these reports have been restricted to carbon metabolism. In this work, we investigate the nitrate reduction (nitrate reductase activity) capacity of tendrils of a semi-leafless variety, Solara, in relation to other leaf structures. Maximum nitrate reductase activity (EC 1.6.6.1), expressed on a protein basis, was significantly lower in tendrils compared to flat structures. However, the activation state of nitrate reductase was significantly higher in tendrils, reaching 70%, compared to flat leaf structures. According to these results, tendrils contributed up to 25% of the overall plant nitrate reduction in the semi-leafless variety. This figure was even higher when nitrate reduction was calculated from in vivo measurements. The results are discussed in relation to nitrate, magnesium, carbohydrates, amino acids and adenylate levels of tendrils.     

豌豆半无叶突变体性状的遗传及在育种上的利用

以半无叶类型、普通类型豌豆为试验材料,对卷须性状的特征特性、遗传规律及在育种上的利用进行了研究。结果表明：半无叶类型豌豆品种卷须极其发达,能够在株间相互缠绕,形成棚架结构,显著地提高了品种的抗倒伏能力,同时改善了群体通风透光性能,显著提高了新品种的产量,是豌豆抗倒伏育种的重要原始材料。半无叶类型属单基因质量性状遗传,显隐性完全,卷须基因af和子叶颜色基因i表现连锁,位于1号染色体上,交换值为5.72%。 Abstract:Using semi-leafless pea and common pea,the authors studied tendril character,its inheritance law and how to use it in pea breeding.The results were as follows:Semi-leafless pea had well developed tendrils;They twined with each other and formed an arbor structure.This ideal structure had greatly increased lodging resistance capability,improved canopy′s air and light level,and remarkably increased new varieties yield.So,semi-leafless pea was one of the most important materials in lodging resistance breeding.Tendril gene,af,and seed color gene i,in semi-leafless pea was linked on chromosome Ⅰ,and cross-over value was 5.72%.     

半无叶型菜豌豆革质膜、甜度性状遗传研究及利用

对半无叶型菜豌豆革质膜、甜度性状的遗传规律进行了研究,结果表明：半无叶型菜豌豆革质膜受两对相对基因控制,F1表现大块革质膜,F2分离出大块革质膜、小块革质膜和无革质膜三种类型,分离比例为9：6：1,并经F2~3试验验证,属于基因互作的积加作用。糖度为数量性状遗传,F2单株间呈连续变异,符合正态分布。选育出的半无叶型菜豌豆新品种“须菜1号”高产、优质,其嫩荚鲜食,嫩卷须作为龙须菜,嫩茎叶也是一种优质蔬菜。     

Growth and Photosynthesis of Mutant Pea Seedlings

The recessive of gene, producing tendrils in place of leaves,and the recessive st gene, reducing stipule size, produce phenotypesof pea that are termed leafless (afafstst) and semi-leafless(afafStSt). Photosynthesis and growth of these two types werecompared with the conventional phenotype (AfAfStSt) during thefirst 9 days of post-emergent growth. The conventional seedlingshowed faster net photosynthesis per unit dry weight than theleafless phenotype, whilst the semi-leafless seedlings wereintermediate. Differences in dark respiration were small butleafless seedlings had significantly higher rates soon afteremergence. Where the three phenotypes used were isogenic, except for ofand st, the rates of shoot growth were in the same ranking orderas net CO₂ uptake. With three other genotypes, representingthe three phenotypes, more similar shoot growth was found betweenthe conventional and semi-leafless phenotype, possibly becauseof compensating differences in embryonic axis size. The ratesof growth of roots and the rates of dry weight loss from thecotyledons showed no consistent differences between phenotypes. The results are discussed in relation to the potential for thesemi-leafless phenotype as an alternative to the conventionalphenotype for the dried pea crop. Pea seedling, Pisum sativum, leafless pea, photosynthesis, seedling growth     

Genetic variability for leaf growth rate and duration under water deficit in sunflower: analysis of responses at cell, organ, and plant level

Plants under water deficit reduce leaf growth, thereby reducing transpiration rate at the expense of reduced photosynthesis. The objective of this work was to analyse the response of leaf growth to water deficit in several sunflower genotypes in order to identify and quantitatively describe sources of genetic variability for this trait that could be used to develop crop varieties adapted to specific scenarios. The genetic variability of the response of leaf growth to water deficit was assessed among 18 sunflower (Helianthus annuus L.) inbred lines representing a broad range of genetic diversity. Plants were subjected to long-term, constant-level, water-deficit treatments, and the response to water deficit quantified by means of growth models at cell-, leaf-, and plant-scale. Significant variation among lines was found for the response of leaf expansion rate and of leaf growth duration, with an equal contribution of these responses to the variability in the reduction of leaf area. Increased leaf growth duration under water deficit is usually suggested to be caused by changes in the activity of cell-wall enzymes, but the present results suggest that the duration of epidermal cell division plays a key role in this response. Intrinsic genotypic responses of rate and duration at a cellular scale were linked to genotypic differences in whole-plant leaf area profile to water deficit. The results suggest that rate and duration responses are the result of different physiological mechanisms, and therefore capable of being combined to increase the variability in leaf area response to water deficit.     

Effect of water deficit on the PSII photochemical phases in two olive trees varieties

The effect of the water deficit, on two olive tree varieties 'Chetoui' and 'Chemlali' at the level of photosystem II photochemistry (PSII) was studied through the following parameters: leaf water potential (Psi(Hb)), quantum yield of PSII (PhiPSII), maximum quantum yield of PSII (Phi(max) PSII), electron transfer rate (J(T)) and photochemical quenching (qP). The results obtained show a reduction in the leaf water potential and a decrease in quantum efficiency of PSII. Besides, electron transfer rate and photochemical quenching showed an increase in response to water deficit. These modifications present some differences according to the variety. These observations are discussed in relation to the strategies developed to grow drought-resistant olive trees in arid areas.     

Characterization of Hormonal Complex in Pea Phenotypes Differing in Leaf Morphology

Two genotypes of the pea (Pisum sativum L.) with wild-type leaves (variety Orlovchanin, Af/Af genotype) and the afila morphotype (aphyllous variety Nord, af/af genotype) were compared in terms of growth performance and hormonal characteristics of different leaf parts and the whole plant. The replacement of leaflets by tendrils in the afila variety led to a reduction in total dry weight and the area of photosynthesizing surfaces. The loss of leaflets was partly compensated for by rapid expansion of stipules at early stages of plant development and by the hypertrophy of tendrils at later stages. The excessive development of stipules in afila plants was paralleled by the increase in IAA and cytokinin level in their tissues. The hypertrophied development of tendrils and chlorophyll accumulation in tendrils of afila plants was correlated with a high IAA and cytokinin content at a low ABA background level. The elevated content of ABA in tissues of wild-type plants was associated with the preferential development of leaflets and a larger transpiratory surface compared with those in the afila form. It is assumed that this feature ensures the turgescence of wild-type plants. The possible involvement of phytohormones in growth and morphogenesis of pea mutants is discussed.     

Differences in the leaf functional traits of six beech (Fagus sylvatica L.) populations are reflected in their response to water limitation

Patterns of intraspecific variation in functional traits have been widely studied across plant species to find out what general suites of traits provide functional advantage under specific environmental conditions. Much less is known about this variation within tree species and, in particular, about its relationship with performance variables such as photosynthetic rates under water deficit. Nevertheless, this knowledge is fundamental to understand the adaptive potential of drought sensitive tree species to increased aridity as predicted in the context of climate change.Intraspecific variation in photosynthetic performance and other leaf functional traits in response to water availability were examined in a glasshouse experiment using seedlings of six European beech populations. The physiological response of seedlings to a “water stress” treatment was compared to a “control” treatment along an experimental cycle of progressive soil water deficit and recovery. We found evidence of intraspecific variation in beech's photosynthetic performance and other leaf functional traits in response to water availability. We also detected intraspecific variation in leaf-level tolerance of water deficit and phenotypic plasticity to water availability suggesting a pattern shaped by both regional and local scale effects. The Swedish population was particularly sensitive to water deficit, being the only population showing impaired photochemical efficiency under the experimental water deficit. Leaf-level tolerance of water deficit was related to PNUE, but not to other functional traits, such as WUE, SLA or leaf nitrogen content, that have been described to vary across species in adaptation to drought tolerance. Our results support the idea that general trends for variation in functional traits across species do not necessarily reflect a similar pattern when observed at the intraspecific level. The observed functional variation between beech populations reaffirms the importance of local adaptation to water deficit in the context of climate change.     

Solar radiation interception by leafless, semi-leafless and leafed peas (Pisum sativum) under contrasting field conditions

Foliage composition, photosynthetic area index (PAI) and radiation interception were measured for crop canopies of leafless (var. Filby), semi-leafless (var. BS3) and leafed (var. Birte) peas (Pisum sativum). Tendrils and petioles contributed more than 60% of total leaf area for leafless peas but less than 30% for semileafless and leafed pea canopies. PAI was related to radiation interception by calculating attenuation coefficients which indicated that leafless peas intercepted more radiation per unit PAI than either semi-leafless or leafed peas. Data interpretation, however, was complicated because of difficulties in estimating the tendril and petiole surface area contribution to PAI. Radiation interception was related to dry matter accumulation by calculating photosynthetic efficiencies. Leafless and semi-leafless peas converted intercepted radiation into dry matter as efficiently as leafed peas. Under conditions of moisture stress, leafed and leafless peas both intercepted radiation more effectively but converted it into dry matter with reduced photosynthetic efficiency.     

Physiological studies on pea tendrils. XIII. Respiration is necessary for contact coiling

When 9 day old light grown pea ( Pisum sativum L. cv. Alaska 2B) plants are irrigated for 4–6 days with 50 μ M 4-chloro-5-(dimethylamino)-2-(α, α, α-trifluoro- m -totyl)-3(2H)-pyridazinone, designated San-6706, the new leaves and tendrils grow morphologically normal, but with neither chlorophyll nor the ability to carry out photosynthesis. Excised tendrils from these plants coil in response to rubbing as well as those from water irrigated controls. Tendrils from San-6706 irrigated plants, which have been dark adapted for 2 or 3 days, proceed to coil when illuminated, just as do those from water irrigated plants. Rubbing of dark adapted tendrils results in an increased respiration rate over the first hour or two, when most of the coiling response occurs. Inhibitor studies indicate that blockage of oxidative phosphorylation, but not of the alternative, cyanide-insensitive, path of respiration, results in a failure of tendrils to coil in response to mechanical perturbation. It is concluded that the normal path of respiration, perhaps via ATP production, may be necessary for thigmosensory perception leading to contact coiling in pea tendrils.     

Differential responses in water use efficiency in two varieties of Catharanthus roseus under drought stress

Two varieties, rosea and alba, of Catharanthus roseus (L.) G. Don. were screened for their water use efficiency under two watering regimes, viz. 60 and 100% filed capacity in the present study. Drought stress was imposed at 60% filed capacity from 30 to 70 days after sowing, while the control pots were maintained at 100% filed capacity throughout the entire growth period. Leaf area duration, cumulative water transpired, water use efficiency, net assimilation rate, mean transpiration rate, harvest index, biomass and yield under the water deficit level were measured from both stressed and well-watered control plants. Water use efficiency significantly increased in both varieties under water stress. Drought stress decreased leaf area duration, cumulative water transpired, net assimilation rate, mean transpiration rate, harvest index, and biomass yield in both varieties studied. Among the varieties, rosea variety showed the best results.     

Rubisco and some chaperone protein responses to water stress and rewatering at early seedling growth of drought sensitive and tolerant wheat varieties

Four wheat varieties differing in their drought tolerance were subjected to severe but recoverable water stress at seedling stage. Growth parameters, leaf water deficit (WD) and electrolyte leakage (EL) were used to evaluate the stress intensity and the extent of recovery. The physiological response of the varieties was quite similar under severe drought. Leaf protein patterns and levels of some individual proteins relevant to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) maintenance were studied in control, stressed and recovering plants by electrophoresis and immunoblotting. The bands representing Rubisco large subunit (RLS), N- and C-terminus of RLS, Rubisco activase (RA) and Rubisco binding protein (RBP, cpn 60), as well as the chaperone and proteolytic subunits of the Clp protease complex were identified using polyclonal antibodies. Under drought conditions RLS, Clp proteases and especially RBP were enhanced, whereas the RA band was only slightly affected. The drought tolerant varieties had higher RBP content in the controls and drought treated plants. Its concentration could be a potential marker for drought tolerance.     

A contribution to the autecology ofphragmites communis Trin. 1. Physiological heterogeneity of leaves

The plantPhragmites communis was subject to an analysis of physiological gradients along the leaf blade and level of insertion of separate leaves. The gradients were established in the following aspects: fresh weight, dry matter, specific leaf area, water content, water saturation deficit and its resaturation, rate of desiccation and photosynthetic capacity. Indistinct gradients under normal conditions become more marked in extreme circumstances. The significance of leaf heterogeneity for all sorts of eco-physiological analysis of the plant under study was discussed.     

Are ABA,ethylene or their interaction involved in the response of leaf growth to soil water deficit? An analysis using naturally occurring variation or genetic transformation of ABA production in maize

The role of abscisic acid (ABA) and its possible interaction with ethylene in mediating leaf elongation response to soil water deficit are a matter of controversy. To address this question, we used a set of maize genotypes with various levels of ABA either due to natural variability or to genetic transformation targeted on NCED/VP14, a key enzyme of ABA synthesis. The transgenic lines yielded less strong phenotypes than available mutants, making it possible to use them under normal growing conditions. We focused on leaf elongation during night periods in order to avoid the confounding effect of ABA on leaf water status. Our results suggest that over a wide range, internal ABA level (measured in both leaf extracts or xylem sap) has no clear effect on leaf elongation response to soil water deficit, except in the case of an antisense line presenting the strongest reduction in ABA accumulation that showed a slight maintenance of leaf elongation during water deficit. Leaf ethylene production rate was variable and not related to water deficit except in the ABA-deficient transgenic lines where it was increased by water deficit on average but not systematically. Moreover, variability in ethylene production rate was not linked to variability in elongation rate. Our results thus suggest that neither ABA nor ethylene seems to play a major role in the control of leaf elongation response to soil water deficit.     

Drought response in self-compatible species of tomato (Solanaceae)

Wild tomatoes occur in habitats from the extremely dry Atacama Desert to moist areas in the Andean highlands, which may have resulted in adaptation of populations or species to differences in soil moisture availability. However, when two accessions representing extremes in habitat water availability from each of the five self-compatible species were grown in a common garden, we observed no differences in leaf physiological responses to soil drought within or between species. All five species had drought avoidance characteristics with the same threshold soil moisture availability for decline of assimilation, stomatal conductance, and leaf water potential (Ψ(l)) in response to slowly decreasing soil moisture. After rewatering, all species rapidly recovered to near predrought Ψ(l), but bulk leaf solute potential after recovery did not indicate any osmotic adjustment. The lack of variation in shoot physiological traits during soil drought is unexpected as water deficit is commonly thought to have imposed selective pressure in the evolution of plant physiology. However, species did differ in assimilation under nonstressed conditions, which may contribute to differential soil water conservation and growth or survival during drought.     

S‐nitrosoglutathione spraying improves stomatal conductance,Rubisco activity and antioxidant defense in both leaves and roots of sugarcane plants under water deficit

Water deficit is a major environmental constraint on crop productivity and performance and nitric oxide (NO) is an important signaling molecule associated with many biochemical and physiological processes in plants under stressful conditions. This study aims to test the hypothesis that leaf spraying of S‐nitrosoglutathione (GSNO), an NO donor, improves the antioxidant defense in both roots and leaves of sugarcane plants under water deficit, with positive consequences for photosynthesis. In addition, the roles of key photosynthetic enzymes ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) in maintaining CO₂ assimilation of GSNO‐sprayed plants under water deficit were evaluated. Sugarcane plants were sprayed with water or GSNO 100 μM and subjected to water deficit, by adding polyethylene glycol (PEG‐8000) to the nutrient solution. Sugarcane plants supplied with GSNO presented increases in the activity of antioxidant enzymes such as superoxide dismutase in leaves and catalase in roots, indicating higher antioxidant capacity under water deficit. Such adjustments induced by GSNO were sufficient to prevent oxidative damage in both organs and were associated with better leaf water status. As a consequence, GSNO spraying alleviated the negative impact of water deficit on stomatal conductance and photosynthetic rates, with plants also showing increases in Rubisco activity under water deficit.     

Sink to Source Transition in Tendrils of a Semileafless Mutant, Pisum sativum cv Curly

Sink to source transition parallels loss of thigmotropic capacity in tendrils of a semileafless mutant, Pisum sativum cv Curly. Macroscopic tendril development is subdivided based on thigmotropic capacity. Stage I is the elongation stage and, although the rate of photosynthesis is similar to that of stage II and III tendrils, dark respiration rates are higher in stage I. During stage II, tendrils are thigmotropic and act as a sink. Even though stage II tendrils have CO₂ exchange characteristics similar to those of stage III tendrils, which are coiled, our fluorescein, ¹⁴C-partitioning, and ¹¹C-translocation experiments suggest that stage I and II tendrils do not export carbon. Only stage III tendrils act as sources of newly fixed carbon. Export from them is blocked by cold, heat girdling of the petiole, or anoxia treatment of the tendrils. A late stage II tendril complex, in which coiling is occurring, may be exporting photoassimilates; however, this phenomenon can be attributed to the fact that the pea leaf is a compound structure and there may be one or more stage III tendrils, no longer thigmotropic, within the tendril complex. Photosynthetic maturity in pea tendrils occurs at stage III and is characterized by the ability of these tendrils to export photoassimilates.