Plant Partitioning Research Articles

The effectiveness of grafting to improve NaCl and CaCl2 tolerance in cucumber

The aim of the current work was to determine whether grafting could improve salinity tolerance of cucumber using three different salt stressors such as CaCl2, NaCl and their combination CaCl2+NaCl with equimolar concentrations, and to study the changes induced by the rootstocks in the shoot growth at agronomical and physiological levels. A greenhouse experiment was carried out to determine yield, growth, fruit quality, SPAD values, electrolyte leakage, chlorophyll fluorescence, CAT, APX, GPX activities and mineral composition and assimilate partitioning of cucumber plants (Cucumis sativus L. cv. ‘Ekron’), either ungrafted or grafted onto two commercial rootstocks: ‘Affyne’ (C. sativus L.) and ‘P360′ (Cucurbita maxima Duch.×Cucurbita moschata Duch.) and cultured in quartziferous sand. Plants were supplied with four nutrient solutions: non-salt control, 20mM CaCl2, 30mM NaCl or 10mM CaCl2+15mM NaCl. Significant depression of yield, and shoot biomass production in response to an increase of salinity concentration in the nutrient solution was observed with more detrimental effects with CaCl2. The three salt types improved fruit quality in both grafting combinations by increasing fruit dry matter and total soluble solids content by 8% and 6%, respectively. The lowest SPAD index and the lowest efficiency of the PSII in dark-adapted leaves, measured as the Fv/Fm ratio were recorded in ungrafted plants treated with CaCl2. Moreover, at the three salt treatments the percentage of yield and biomass reduction in comparison to control was significantly lower in the plants grafted onto ‘P360′ and especially ‘Affyne’ than ungrafted plants, with the highest yield, and shoot reduction recorded with CaCl2 in comparison to those recorded with NaCl and CaCl2+NaCl treatments. Grafted cucumber plants exposed to NaCl and CaCl2+NaCl were capable of maintaining higher chlorophyll content (SPAD index), higher photochemical activity of PSII, increased the capacity of antioxidant system by enhancing the GPX activity, a better nutritional status (higher N, K, and Ca, and lower Na) in the shoot tissues and a higher membrane selectivity in comparison with ungrafted ones. The higher crop performance of grafted (Ekron/Affyne) cucumber recorded with NaCl than with CaCl2, was attributed to the limited capability of the rootstocks to restrict Cl− shoot uptake, thus Cl−, which continues passing to the leaves, becomes the more significant toxic component of the saline solution.

32S/34S isotope fractionation in plant sulphur metabolism

Summary Sulphur is a crucial microelement for plant metabolism, involved in response mechanisms to oxidative stress, C1 metabolism, electron transfer, secondary metabolism and post‐translational peptide modifications. However, relatively little is known about sulphur transport and partitioning in plants. Although key steps of sulphur assimilation have been shown using labelling with radioactive 35S in past decades, the use of a natural tracer, allowing the examination of metabolic commitments and mass balance, is desirable. Sulphur stable isotopes (32S and 34S) have been proven to be useful for the investigation of the origin of sulphur atoms in geochemistry and for the detection of the origin of sulphur atoms. Nevertheless, their use for the study of primary sulphur metabolism has been impeded by our lack of knowledge of 32S/34S isotope fractionations and convenient methods for δ34S analyses. Here, we review documented 32S/34S isotope fractionations that may apply to sulphur metabolism, and explain how they should yield disparities amongst sulphur‐containing plant compounds.

갯메꽃의 수분스트레스에 대한 물질분배 특성

Dry matter allocation characteristics of Calystegia soldanella, grown in pots, was analysed to assess its plasticity in response to water-stressed conditions. As water was withheld leaf water potential between the two watering treatments was similar during the first 6 days, followed by a rapid decrease in water-stressed plants. The minimum leaf water potential was -1.50 MPa on day 15 and the maximum leaf water potential was about -0.5 MPa on day 0 in water-stressed plants. In well-watered plants leaf water potential was maintained almost consistently throughout the experiment. There was no significant difference in plant dry weight between the two watering treatments for 9 days after the start of experiment and that was remarkably increased thereafter, compared with that remained without any increase in water-stressed plants. In dry mass partitioning, however, the water-stressed plants showed a great plasticity, showing that there were 1.81, 1.35 and 0.81 times increase in root, stem and leaf, respectively. Dry mass partitioning in well-watered plants varied from 2% to 5%. The difference of dry mass partitioning between the two watering treatments was reflected in leaf mass per unit area (LMA) and root/shoot (R/S) ratio. LMA in water-stressed plants was lower than that in well-watered plants, while R/S ratio in water-stressed plants was higher in well-watered plants. This means that the water-stressed plants reduced its leaf area and increased dry mass partitioning into root and stem during the progress of soil drying. These results indicate that Calystegia soldanella inhabiting in sand dune cope with water stress with high plasticity which can adjust its dry mass partitioning according to soil water conditions.

Morphogenic responses of two Brachiaria genotypes to clipping frequency

Tropical grasslands represent an important resource for the Brazilian cattle industry, which is heavily dependent on grazed pastures. Total pasture area in the country totals 196 Mha (23% of the country’s land area) (FAO 2013). The genus Brachiaria represents around 85% of cultivated pastures in Brazil (Moreira et al. 2009), 40% of which are established with B. brizantha cv. Marandu (Barbosa 2006). Mulato II is a new hybrid brachiariagrass cultivar, which has been developed to improve agronomic characteristics, broaden the range of adaptation, and ensure high forage production and nutritive value. It has also been viewed as a means of reducing the dependence on the Marandu palisadegrass monoculture (Argel et al. 2007). The use of new cultivars should be based on adequate understanding of physiological processes and growth potential under a range of management practices. Morphogenic characteristics allow for accessing herbage accumulation potential through the measurement of tissue synthesis and senescence in forage plants. Management practices such as defoliation frequency can modify assimilate partitioning in the forage plant, affecting morphogenic characteristics related to growth rate and forage nutritive value. The objective of this research was to describe and explain morphogenic differences between Marandu palisadegrass and Mulato II brachiariagrass as affected by harvest frequency.

Physiological Studies on Ratoonability of Sugarcane Varieties under Tropical Indian Condition

The ratoon crop occupies approximately 40% of the total area of sugarcane crop in tropical India. The main reason for the lower average cane productivity is the yield decline in ratoon crops (40 - 50 t/ha) despite the release of the high yielding varieties and advanced cane production technology. The physiological factors associated with ratooning performance and the variation in growth and yield were studied in 11 sugarcane varieties in two cycles of one plant and two ratoon crops each. The first ratoon and second ratoon crop showed 17.0% and 28.1% reduction in tiller production and 15.5% and 15.7% reduction in NMC, respectively, over plant crop. The differences in growth parameters between the plant and ratoon crops at the formative phase were lesser than that of grand growth and maturity phases. Varieties Co 86032, Co 97008, Co 95020 Co 99004 and Co 2000-10 showed better physiological efficiency in terms of plant height, shoot population, leaf size, TDMP, partitioning efficiency, chlorophyll content and nitrate reductase activity and significantly higher yield components such as NMC, SCW, cane length, internodal length as well as cane yield compared to other varieties. The higher reduction in ratoon yield in Co 99008, Co 94012, Co 8021 and Co 97009 (>35.00% reduction) was due to higher reduction in tiller production associated with stunted plant growth and root system, reducetion in individual leaf size and LAI, TDMP, total chlorophyll content, NMC, internodal length and SCW. The results obtained indicated that the plant height, TDMP, stem partitioning, leaf size, total chlorophyll content, SCW, cane length and cane girth were highly associated with yield of first and second ratoon crops than that of plant crop. Therefore the difference in the association between physiological parameters with yield of plant and ratoon crops therefore decides the ratooning potential of the crop.

Photosynthetic acclimation and resource use by the C3 and C4 subspecies of Alloteropsis semialata in low CO2 atmospheres

During the past 25Myr, partial pressures of atmospheric CO2 (Ca ) imposed a greater limitation on C3 than C4 photosynthesis. This could have important downstream consequences for plant nitrogen economy and biomass allocation. Here, we report the first phylogenetically controlled comparison of the integrated effects of subambient Ca on photosynthesis, growth and nitrogen allocation patterns, comparing the C3 and C4 subspecies of Alloteropsis semialata. Plant size decreased more in the C3 than C4 subspecies at low Ca , but nitrogen pool sizes were unchanged, and nitrogen concentrations increased across all plant partitions. The C3, but not C4 subspecies, preferentially allocated biomass to leaves and increased specific leaf area at low Ca . In the C3 subspecies, increased leaf nitrogen was linked to photosynthetic acclimation at the interglacial Ca , mediated via higher photosynthetic capacity combined with greater stomatal conductance. Glacial Ca further increased the biochemical acclimation and nitrogen concentrations in the C3 subspecies, but these were insufficient to maintain photosynthetic rates. In contrast, the C4 subspecies maintained photosynthetic rates, nitrogen- and water-use efficiencies and plant biomass at interglacial and glacial Ca with minimal physiological adjustment. At low Ca , the C4 carbon-concentrating mechanism therefore offered a significant advantage over the C3 type for carbon acquisition at the whole-plant scale, apparently mediated via nitrogen economy and water loss. A limiting nutrient supply damped the biomass responses to Ca and increased the C4 advantage across all Ca treatments. Findings highlight the importance of considering leaf responses in the context of the whole plant, and show that carbon limitation may be offset at the expense of greater plant demand for soil resources such as nitrogen and water. Results show that the combined effects of low CO2 and resource limitation benefit C4 plants over C3 plants in glacial-interglacial environments, but that this advantage is lessened under anthropogenic conditions.

Is the recovery of (photo) respiratory CO2 and intermediates minimal?

Is the recovery of (photo) respiratory <scp>CO</scp>₂ and intermediates minimal?

Ectomycorrhiza affect architecture and nitrogen partitioning of beech (Fagus sylvatica L.) seedlings under shade and drought

The aim of this study was to investigate the influence of ectomycorrhizal fungi (EMF) on the architecture of and nitrogen (N) partitioning in young beech (Fagus sylvatica) plants in response to different light regimes and water deprivation. We hypothesized that EMF modify biomass partitioning and architecture of young beech plants by increased N uptake in comparison with non-mycorrhizal (NM) plants and that therefore, the drought responses of EM and NM plants diverge. We anticipated that full light-exposed plants were more drought tolerant due to improved water status and nutrition, whereas shade-acclimated EM plants were more drought susceptible because of decreased mycorrhizal colonization. To test these hypotheses seedlings were grown in native or sterilized forest soil. To avoid effects of soil pretreatment NM and EM plants were transplanted into sand-peat culture systems and exposed to shade, drought or the combination of both factors. Shade resulted in reduced root biomass production decreasing the root-to-shoot ratio. Mild drought stress (pre-dawn water potential [Ψpd]=−1.3MPa) did not affect biomass partitioning. EMF colonization did not increase plant biomass, but had strong effects on root architecture: the numbers of root tips as well as the absolute and specific root lengths were increased because of formation of thin roots, especially in the diameter classes from 0.2 to 0.8mm. In contrast to our expectation N uptake of well irrigated EM plants was not increased despite their larger potential for soil exploitation. Overall, EM plants exhibited higher amounts of carbon fixed per unit of N taken up than NM plants and shifted N partitioning towards the roots. Beneficial effects of EMFs were apparent under mild drought but the responses differed depending on the light availability: shaded EM plants showed a delay in the decrease of Ψpd; light exposed EM plants showed increased N uptake compared with NM beeches. These results indicate that EMFs are involved in mediating divergent responses of beech to drought depending on the light availability.

Modeling Temperature Responses of Leaf Growth, Development, and Biomass in Maize with MAIZSIM

Mechanistic crop models capable of representing realistic temperature responses of key physiological processes are necessary for enhancing our ability to forecast crop yields and develop adaptive cropping solutions for achieving food security in a changing climate. Leaf growth and phenology are critical components of crop growth and yield that are sensitive to climate impacts. We developed a novel modeling approach that incorporates a set of nonlinear functions to augment traditional thermal time methods (e.g., growing degree days) for simulating temperature responses of leaf expansion and phenology in maize or corn (Zea mays L.). The resulting leaf expansion and phenology models have been implemented into a new crop model, MAIZSIM, that simulates crop growth based on key physiological and physical processes including C4 photosynthesis, canopy radiative transfer, C partitioning, water relations, and N dynamics for a maize plant. Coupled with a two‐dimensional soil process model, 2DSOIL, MAIZSIM was applied to simulate leaf growth, phenology, biomass partitioning, and overall growth of maize plants planted at two field sites on the Eastern Shore of Maryland and in Delaware for 3 yr of data. The model parameters were estimated using data from outdoor sunlit growth chambers and the literature. No calibration was performed using the field data. The MAIZSIM model simulated leaf area, leaf addition rate, leaf numbers, biomass partitioning and accumulation with reasonable accuracy. Our study provides a feasible method for integrating nonlinear temperature relationships into crop models that use traditional thermal time approaches without sacrificing their current structure for predicting the climate change impacts on crops.

Multiple impacts of the plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2 on nutrient and ABA relations of Pisum sativum.

Resolving the physiological mechanisms by which rhizobacteria enhance plant growth is difficult, since many such bacteria contain multiple plant growth-promoting properties. To understand further how the 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCd)-containing rhizobacterium Variovorax paradoxus 5C-2 affects plant growth, the flows and partitioning of mineral nutrients and abscisic acid (ABA) and ABA metabolism were studied in pea (Pisum sativum) plants following rhizosphere bacterial inoculation. Although root architecture was not affected, inoculation increased root and shoot biomass, and stomatal conductance, by 20, 15, and 24%, respectively, and increased N, P, K, Ca, and Mg uptake by 16, 81, 50, 46, and 58%, respectively. P deposition in inoculated plant roots was 4.9 times higher than that in uninoculated controls. Rhizobacterial inoculation increased root to shoot xylem flows and shoot to root phloem flows of K by 1.8- and 2.1-fold, respectively. In control plants, major sinks for K deposition were the roots and upper shoot (43% and 49% of total uptake, respectively), while rhizobacterial inoculation increased K distribution to the lower shoot at the expense of other compartments (xylem, phloem, and upper shoot). Despite being unable to metabolize ABA in vitro, V. paradoxus 5C-2 decreased root ABA concentrations and accumulation by 40–60%. Although inoculation decreased xylem ABA flows, phloem ABA flows increased. Whether bacterial ACCd attenuates root to shoot ABA signalling requires further investigation, since ABA is critical to maintain growth of droughted plants, and ACCd-containing organisms have been advocated as a means of minimizing growth inhibition of plants in drying soil.

Pre and post-severance effects of light quality on carbohydrate dynamics and microcutting adventitious rooting of two Eucalyptus species of contrasting recalcitrance

Adventitious rooting is a complex developmental response affected by genetic and environmental factors. Radiation quality effects on adventitious rooting depend on characteristics such as species, growth stage, irradiance, spectral quality, and time of exposure. Eucalyptus is an essential genus for the paper industry, and high yield plantations depend on adventitious rooting of selected genotypes. This work addressed two hypotheses: (1) radiation quality equally affects adventitious rooting in Eucalyptus species of different recalcitrance; (2) adventitious rooting outcome depends on both donor plant and cutting radiation quality treatments. To that end, the easy-to-root Eucalyptus grandis and the recalcitrant Eucalyptus globulus were evaluated. The effect of white, blue, red and far-red radiation enrichment on microcuttings and donor plants of both species was evaluated in relation to rooting. There was no effect of radiation quality on adventitious rooting of E. grandis or when radiation treatments were applied to E. globulus microcuttings. In contrast, donor plants of E. globulus, grown in medium devoid of sucrose and exposed to far-red radiation, yielded microcuttings showing higher rooting percentage, even in the absence of exogenous auxin in the rooting medium. Sucrose in donor plant medium abolished the positive effect of far-red radiation. An increase in endogenous soluble sugars and starch contents in basal microcuttings was associated with far-red radiation treatment of donor plants. These results underline the importance of appropriate carbohydrate partitioning in donor plants for adventitious rooting of cuttings and provide a basis for understanding and overcoming rooting recalcitrance in E. globulus clones.

Reuteran and levan as carbohydrate sinks in transgenic sugarcane

The present study reports the effect of high molecular weight bacterial fructan (levan) and glucan (reuteran) on growth and carbohydrate partitioning in transgenic sugarcane plants. These biopolymers are products of bacterial glycosyltransferases, enzymes that catalyze the polymerization of glucose or fructose residues from sucrose. Constructs, targeted to different subcellular compartments (cell wall and cytosol) and driven by the Cauliflower mosaic virus-35S: maize-ubiquitin promoter, were introduced into sugarcane by biolistic transformation. Polysaccharide accumulation severely affected growth of callus suspension cultures. Regeneration of embryonic callus tissue into plants proved problematic for cell wall-targeted lines. When targeted to the cytosol, only plants with relative low levels of biopolymer accumulation survived. In internodal stalk tissue that accumulate reuteran (max 0.03mg/g FW), sucrose content (ca 60mg/g FW) was not affected, while starch content (<0.4mg/g FW) was increased up to four times. Total carbohydrate content was not significantly altered. On the other hand, starch and sucrose levels were significantly reduced in plants accumulating levan (max 0.01mg/g FW). Heterologous expression resulted in a reduction in total carbohydrate assimilation rather than a simple diversion by competition for substrate.

Inactivation of thioredoxin f1 leads to decreased light activation of ADP‐glucose pyrophosphorylase and altered diurnal starch turnover in leaves of Arabidopsis plants

Chloroplast thioredoxin f (Trx f) is an important regulator of primary metabolic enzymes. However, genetic evidence for its physiological importance is largely lacking. To test the functional significance of Trx f in vivo, Arabidopsis mutants with insertions in the trx f1 gene were studied, showing a drastic decrease in Trx f leaf content. Knockout of Trx f1 led to strong attenuation in reductive light activation of ADP-glucose pyrophosphorylase (AGPase), the key enzyme of starch synthesis, in leaves during the day and in isolated chloroplasts, while sucrose-dependent redox activation of AGPase in darkened leaves was not affected. The decrease in light-activation of AGPase in leaves was accompanied by a decrease in starch accumulation, an increase in sucrose levels and a decrease in starch-to-sucrose ratio. Analysis of metabolite levels at the end of day shows that inhibition of starch synthesis was unlikely due to shortage of substrates or changes in allosteric effectors. Metabolite profiling by gas chromatography-mass spectrometry pinpoints only a small number of metabolites affected, including sugars, organic acids and ethanolamine. Interestingly, metabolite data indicate carbon shortage in trx f1 mutant leaves at the end of night. Overall, results provide in planta evidence for the role played by Trx f in the light activation of AGPase and photosynthetic carbon partitioning in plants.

Salt marsh macrophyte Phragmites australis strategies assessment for its dominance in mercury-contaminated coastal lagoon (Ria de Aveiro, Portugal)

The dominance of a plant species in highly metal-contaminated areas reflects its tolerance or adaptability potential to these scenarios. Hence, plants with high adaptability and/or tolerance to exceptionally high metal-contaminated scenarios may help protect environmental degradation. The present study aimed to assess the strategies adopted by common reed, Phragmites australis for its dominance in highly mercury-contaminated Ria de Aveiro coastal lagoon (Portugal). Both plant samples and the sediments vegetated by monospecific stand of Phragmites australis were collected in five replicates from mercury-free (reference) and contaminated sites during low tide between March 2006 and January 2007. The sediments’ physico-chemical traits, plant dry mass, uptake, partitioning, and transfer of mercury were evaluated during growing season (spring, summer, autumn, and winter) of P. australis. Redox potential and pH of the sediment around roots were measured in situ using a WTW-pH 330i meter. Dried sediments were incinerated for 4 h at 500°C for the estimation of organic matter whereas plant samples were oven-dried at 60°C till constant weight for plant dry mass determination. Mercury concentrations in sediments and plant parts were determined by atomic absorption spectrometry with thermal decomposition, using an advanced mercury analyzer (LECO 254) and maintaining the accuracy and precision of the analytical methodologies. In addition, mercury bioaccumulation and translocation factors were also determined to differentiate the accumulation of mercury and its subsequent translocation to plant parts in P. australis. P. australis root exhibited the highest mercury accumulation followed by rhizome and leaves during the reproductive phase (autumn). During the same phase, P. australis exhibited ≈5 times less mercury-translocation factor (0.03 in leaf) when compared with the highest mercury bioaccumulation factor for root (0.14). Moreover, seasonal variations differentially impacted the studied parameters. P. australis’ extraordinary ability to (a) pool the maximum mercury in its roots and rhizomes, (b) protect its leaf against mercury toxicity by adopting the mercury exclusion, and (c) adjust the rhizosphere-sediment environment during the seasonal changes significantly helps to withstand the highly mercury-contaminated Ria de Aveiro lagoon. The current study implies that P. australis has enough potential to be used for mercury stabilization and restoration of sediments/soils rich in mercury as well.

Grafting cucumber plants enhance tolerance to sodium chloride and sulfate salinization

The aim of the current work was to determine whether grafting could improve salinity tolerance of cucumber using two different salt stressors such as NaCl and Na2SO4 with equimolar concentrations, and to study the changes induced by the rootstock in the shoot growth at agronomical and physiological levels. A greenhouse experiment was carried out to determine yield, growth, fruit quality, leaf gas exchange, electrolyte leakage, SPAD, and mineral composition and assimilate partitioning of cucumber plants (Cucumis sativus L. cv. ‘Akito’), either ungrafted or grafted onto the commercial rootstock ‘PS1313’ (Cucurbita maxima Duch.×Cucurbita moschata Duch.) and cultured in quartziferous sand. Plants were supplied with three nutrient solutions: non-salt control, 27mM Na2SO4, or 40mM NaCl. Significant depression of yield, shoot and root biomass production in response to an increase of salinity concentration in the nutrient solution was observed with more detrimental effects with NaCl treatment. The two salt treatments, especially NaCl, inhibited photosynthesis, pigment synthesis, and membrane integrity. Salinity with NaCl and Na2SO4 improved fruit quality in both grafting combinations by increasing fruit dry matter and total soluble solids content. Moreover, at the two salt treatments the percentage of yield and biomass reduction in comparison to control was significantly lower in the plants grafted onto ‘PS1313’ than ungrafted plants, with the highest yield, shoot and root reduction recorded with NaCl in comparison to those recorded with Na2SO4 treatment. Grafted cucumber plants exposed to Na2SO4 were capable of maintaining higher net assimilation rates, higher chlorophyll content (SPAD index), a better nutritional status (higher K, Ca and Mg and lower Na) in the shoot tissues and higher membrane selectivity in comparison with ungrafted ones. The higher crop performance of grafted cucumber recorded with Na2SO4 than with NaCl, was attributed to the inability of the rootstock to restrict Cl− shoot uptake, thus Cl−, which continues passing to the leaves, becomes the more significant toxic component of the saline solution.

Influence of NaCl Salinity and Different Substracts on Plant Growth, Mineral Nutrient Assimilation and Fruit Yield of Strawberry

A hydroponic culture was carried out with strawberry cv. Camarosa to investigate the effects of four salinity levels and four different substrates on plant growth, mineral nutrient assimilation and fruit yield of strawberry. Total dry weight accumulation of plants was not inhibited at low salinities, but it was significantly inhibited at 60 mM NaCl. Dry mass (DM) partitioning in NaCl-stressed plants was in favor of crown and petioles and at the expense of root, stem and leaf, whereas leaf, stem and root DM progressively declined with an increase in salinity. Specific leaf area (SLA) and leaf area ratio (LAR) significantly decreased in cv. Camarosa at 60 and 90 mM. Results also showed that the presence of NaCl in the root medium induced an increase in total Na+ content of the plants in the shoot and root. Despite Na+ and K+, the increase in total inorganic ions resulted from increasing salinity, with Ca2+ and Mg2+ concentrations decreasing in shoot and increasing in roots with an increase in salinity. For all micro- and macroelements however, significant concentration changes related to different substrates were not detected in the present experiments. Results also showed a significant decline of Fe content of 40% and 49% in shoot and root, respectively.

A Novel Arabidopsis Vacuolar Glucose Exporter Is Involved in Cellular Sugar Homeostasis and Affects the Composition of Seed Storage Compounds

Subcellular sugar partitioning in plants is strongly regulated in response to developmental cues and changes in external conditions. Besides transitory starch, the vacuolar sugars represent a highly dynamic pool of instantly accessible metabolites that serve as energy source and osmoprotectant. Here, we present the molecular identification and functional characterization of the vacuolar glucose (Glc) exporter Arabidopsis (Arabidopsis thaliana) Early Responsive to Dehydration-Like6 (AtERDL6). We demonstrate tonoplast localization of AtERDL6 in plants. In Arabidopsis, AtERDL6 expression is induced in response to factors that activate vacuolar Glc pools, like darkness, heat stress, and wounding. On the other hand, AtERDL6 transcript levels drop during conditions that trigger Glc accumulation in the vacuole, like cold stress and external sugar supply. Accordingly, sugar analyses revealed that Aterdl6 mutants have elevated vacuolar Glc levels and that Glc flux across the tonoplast is impaired under stress conditions. Interestingly, overexpressor lines indicated a very similar function for the ERDL6 ortholog Integral Membrane Protein from sugar beet (Beta vulgaris). Aterdl6 mutant plants display increased sensitivity against external Glc, and mutant seeds exhibit a 10% increase in seed weight due to enhanced levels of seed sugars, proteins, and lipids. Our findings underline the importance of vacuolar Glc export during the regulation of cellular Glc homeostasis and the composition of seed reserves.

Evaluation of Irrigation Practices for Growth, Biomass Production, and Nutrient Partitioning in Eucalyptus camaldulensis Plants in Indian Dry Zone

Supplemental irrigation is essential to increase tree productivity in dry areas to fulfill the local needs. One-year-old Eucalyptus camaldulensis Dehnh plants were planted in July 1998 and supplemental irrigation was provided at 36.2 mm (I1), 26.5 mm (I2), 20.2 mm (I3), 18.1 mm (I4), and live saving (I5). Frequency and quantity of irrigation increased with an increase in irrigation level enhancing plant height, collar diameter, and biomass. These variables were highest at I1, but water use efficiency (WUE) was highest at I2. Dry biomass production increased from 1.18 kg plant−1 at I5 to 13.75 kg plant−1 at I1 at 24-month age. Biomass allocation to root increased from I1 to I5 but it was at the expense of leaf and branches. Height, collar diameter, dry biomass, and nutrient uptake indicated a non-linear increase with total quantity of water. Partitioning of N, Mg, Fe, Mn, Cu, and Zn was greater to stem; and those of P, K, and Ca was greater to leaf than to the other parts. Conclusively, I3 and I4 levels supported establishment whereas I2 level was best for growth and productivity of E. camaldulensis plants in dry areas. The I1 level could be tried to increase water use and reduce salinity buildup.

Complexation and detoxification of Zn and Cd in metal accumulating plants

Metal accumulating plants exposed to toxic levels of zinc (Zn) and cadmium (Cd) uptake metals through extracellular and intracellular complexation with inorganic and organic ligand formation. However, little is known about the nature and formation mechanism of these metal–ligand complexes. Though, Zn and Cd have many similar chemical properties, yet their complexation and compartmentalization in plants vary with plant species. In principal, the question arises what factors govern Zn and Cd partitioning in plants? What form of the metal is taken up by the root, and is further distributed and accumulated in both vegetative and reproductive tissues? Therefore, the aim of present study is to address several questions concerning the mechanisms of Zn and Cd coordination and compartmentalization in plants using X-ray absorption spectroscopy (XAS) technique. XAS allows direct determination of elemental oxidation states and coordination environments in different plant tissues. This review article briefly explains some other important techniques of XAS; EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure), which are employed for determining Zn and Cd complexation within the plant. Therefore, In present review, the predominant as well as the minor chemical forms of Zn and Cd present in particular plant tissue have been discussed which could give better insight towards metal accumulation and detoxification mechanisms operated in plants. This information could assist in employing suitable hyperaccumulator plants for metal phytoextraction and reclamation of metal contaminated sites.

Validation of a Crop Yield and CO2 Fixation Model over Southeast Asia by Carbon Partitioning in Grain Plants

A photosynthetic-sterility model for grain production monitoring has been developed and validated under the background of climate change and Asian economic growth in developing countries. This paper presents an application of the model to evaluate carbon-fixation rates in yields of paddy rice, winter wheat, and maize in Asia. The validation of the model is based on carbon partitioning in grain plants. The carbon hydrate in grains has the same chemical formula as that of cellulose in grain vegetation. The partitioning of carbon in plants can validate fixation amounts of computed carbon using a satellite-based photosynthesis model. The model estimates the photosynthesis fixation of rice reasonably in Japan and China. Results were validated through examination of carbon in grains, but the model tends to underestimate results for winter wheat and maize. This study also provides daily distributions of the PSN, which is the CO2 fixation in Asian areas combined with a land-cover distribution classified from MODIS data, NDVI from SPOT VEGETATION, and meteorological re-analysis data by European Centre for Medium-Range Forecasts (ECMWF). The mean CO2 and carbon fixation rates in paddy areas were 25.92 (t CO2/ha) and 5.28 (t C/ha) in Japan, respectively. Comparisons between the model’s values and MODIS seasonal PSNs show similar trends. The writers are preparing to compare computed photosynthesis rates with observed AsiaFlux data for the validation of this model at field sites of paddy, grassland and forests in Japan and Asian countries.