In vitro photoautotrophic acclimatization,direct transplantation and ex vitro adaptation of rubber tree (<Emphasis Type="Italic">Hevea brasiliensis</Emphasis>)

We investigated the effect of carbon dioxide (CO₂)-ambient (350 µmol CO₂ mol^?1) and CO₂-enriched (1500 µmol CO₂ mol^?1) conditions of in vitro photoautotrophic system on two cultivars, ‘RRIM600’ and ‘RRIT413’ of rubber tree (Hevea brasiliensis) in an acclimatization process of 45 days. Survival percentage of in vitro rubber tree plantlets derived from somatic embryos under ambient CO₂ was better than those under CO₂-enriched conditions, especially in cv. ‘RRIT413’. Subsequently, the survival rate of ex vitro transplanted plantlets was similar to the in vitro plantlets and abnormal morphological characters such as light-green leaves (SPAD), small leaves in cv. ‘RRIT413’ acclimatized under CO₂-enriched conditions were demonstrated 30 days after the plantlets were transferred into the soil. Maximum quantum yield of PSII, photon yield of PSII, stomatal conductance and transpiration rate in cv. ‘RRIT413’ acclimatized under CO₂-enriched conditions were sharply declined by 39.0, 50.6, 47.1 and 45.8%, respectively as compared to those acclimatized under ambient CO₂ conditions. In contrast, the in vitro acclimatized plantlets of cv. ‘RRIM600’ were un-responsive under both ambient- and enriched-CO₂ conditions. In conclusion, genotypic dependent in response to CO₂ enriched conditions in in-vitro acclimatization of rubber tree plantlets was evidently demonstrated as a key result to regulate plant growth and development in ex vitro environments. Interestingly, soluble sugar contents (sucrose, glucose and fructose) were increased after transplanting the plantlets of cv. ‘RRIM600’ acclimatized under CO₂-enriched condition into the soil and thus, can be considered as an adaptive indicator of ex vitro adaptation.     

Isolation,expression, and functional analysis of developmentally regulated plasma membrane polypeptide 1 (DREPP1) in <Emphasis Type="Italic">Sporobolus virginicus</Emphasis> grown under alkali salt stress

The plant specific DREPP proteins have been shown to bind Ca²⁺ and regulate the N-myristoylation signaling and microtubule polymerization in Arabidopsis thaliana. The information about DREPP proteins in other plants is, however, scarce. In the present study, we isolated the DREPP gene from a halophytic grass, Sporobolus virginicus, and tested whether the gene was involved in alkaline salt stress responses. The SvDREPP1 was cloned from S. virginicus by RACE methods. The isolated gene showed high homology to DREPP homologs from C₄ grasses, Setaria italica, and Panicum hallii as well as rice (OsDREPP1). The encoded protein contained 202 amino acid residues. It was expressed in E. coli, and its biochemical properties were studied. It was observed that SvDREPP1 was not only Ca²⁺-binding protein, but also bind to calmodulin and microtubules. The SvDREPP1 mRNA expression in plants grown under alkaline salt stress was upregulated by 3.5 times over the control in leaf tissues after 48-h treatment, whereas it was increased for 6.0 times in the root tissues at 36 h. The data suggests the importance of SvDREPP1 in regulating alkali salt stress responses in the leaf tissues.     

Expression and functional analysis of putative vacuolar Ca2+-transporters (CAXs and ACAs) in roots of salt tolerant and sensitive rice cultivars

Vacuolar Ca²⁺-transporters could play an important role for salt tolerance in rice (Oryza sativa L.) root. Here, we compared the expression profiles of putative vacuolar cation/H⁺ exchanger (CAX) and calmodulin-regulated autoinhibited Ca²⁺-ATPase (ACA) in rice roots of salt tolerant cv. Pokkali and salt sensitive cv. IR29. In addition to five putative vacuolar CAX genes in the rice genome, a new CAX gene (OsCAX4) has been annotated. In the present study, we isolated the OsCAX4 gene and showed that its encoded protein possesses a unique transmembrane structure and is potentially involved in transporting not only Ca²⁺ but also Mn²⁺ and Cu²⁺. These six OsCAX genes differed in their mRNA expression pattern in roots of tolerant versus sensitive rice cultivars exposed to salt stress. For example, OsCAX4 showed abundant expression in IR29 (sensitive) upon prolonged salt stress. The mRNA expression profile of four putative vacuolar Ca²⁺-ATPases (OsACA4-7) was also examined. Under control conditions, the mRNA levels of OsACA4, OsACA5, and OsACA7 were relatively high and similar among IR29 and Pokkali. Upon salt stress, only OsACA4 showed first a decrease in its expression in Pokkali (tolerant), followed by a significant increase. Based on these results, a role of vacuolar Ca²⁺ transporter for salt tolerance in rice root was discussed.     

Responses of Nipa palm (Nypa fruticans) seedlings,a mangrove species,to salt stress in pot culture

Nipa palm (Nypa fruticans) is the only palm that grows in mangrove vegetation. We investigated the effect of salt stress on the growth and physiology of 6-month-old seedlings of Nipa palm exposed to different degrees of salt stress (as NaCl) in pot culture. The overall growth performance of Nipa palm was unaffected by mild salt stress (8.9−16.6 dS m⁻¹), whereas seedlings grown under severe salt stress (EC = 57.2 dS m⁻¹) had lower chlorophyll content and fluorescence, reduced net photosynthesis and transpiration, which resulted in reduced growth of the plants. Na⁺ contents in leaf, petiole, and root tissues increased considerably under salt stress, depending upon the NaCl levels in the soil solution. Under salt-stress K⁺ content declined, whereas Ca²⁺ content increased somewhat, in parallel to Na⁺. Free proline accumulated in plants growing under high salt stress (EC = 57.2 dS m⁻¹). In contrast, soluble sugars were enriched under intermediate levels of salt stress (EC = 16.6 dS m⁻¹). The results obtained in the present study suggest that, based on ecophysiological data, N. fruticans is a species best adapted to grow in mangrove coastal areas with moderate only salt load, and circumscribing quite well the actual areas of occurrence of this palm in the gradient from seawater habitats to inland sites. © 2014 Elsevier GmbH     

Physio-morphological traits and osmoregulation strategies of hybrid maize (Zea mays) at the seedling stage in response to water-deficit stress

Drought has been identified as a major factor restricting maize productivity worldwide, especially in the rainfed areas. The objective of the present study was to investigate the physiological adaptation strategies and sugar-related gene expression levels in three maize (Zea mays L.) genotypes with different drought tolerance abilities (Suwan4452, drought tolerant as a positive check; S7328, drought susceptible as a negative check; Pac339, drought susceptible) at the seedling stage. Ten-day old seedlings of maize genotypes were subjected to (i) well-watered (WW) or control and (ii) water-deficit (WD) conditions. Leaf osmotic potential of cv. S7328 under WD was significantly decreased by 1.35–1.45 folds compared with cv. Pac339 under WW, whereas it was retained in cv. Suwan4452, which utilized total soluble sugars as the major osmolytes for maintaining leaf greenness, F_v/F_m, Φ_PSII, and stomatal function (P_n, net photosynthetic rate; g_s, stomatal conductance; and E, transpiration rate). Interestingly, sucrose degradation (65% over the control) in cv. Pac339 under WD was evident in relation to the downregulation of the ZmSPS1 level, whereas glucose enrichment (1.65 folds over the control) was observed in relation to the upregulation of ZmSPS1 and ZmSUS1. Moreover, CWSI (crop water stress index), calculated from leaf temperature of stressed plants, was negatively correlated with E, g_s, and P_n. Overall, growth characteristics, aboveground and belowground parts, in the drought-susceptible cv. Pac339 and cv. S7328, were significantly decreased (> 25% over the control), whereas these parameters in the drought-tolerant cv. Suwan4452 were unaffected. The study validates the use of leaf temperature, CWSI, P_n, g_s, and E as sensitive parameters and overall growth characters as effective indices for drought tolerance screening in maize genotypes at the seedling stage. However, further experiments are required to validate the results observed in this study under field conditions.

     

Expression levels of vacuolar ion homeostasis-related genes,Na+ enrichment,and their physiological responses to salt stress in sugarcane genotypes

Protoplasma - Sugarcane is a sugar-producing crop widely grown in tropical regions in over 120 countries of the world. Salt-affected soil is one of the most significant abiotic constraints that...     

3D Porous Cu–Zn Alloys as Alternative Anode Materials for Li‐Ion Batteries with Superior Low T Performance

Zinc is recently gaining interest in the battery community as potential alternative anode material, because of its large natural abundance and potentially larger volumetric density than graphite. Nevertheless, pure Zn anodes have shown so far very poor cycling performance. Here, the electrochemical performance of Zn‐rich porous Cu–Zn alloys electrodeposited by an environmentally friendly (aqueous) dynamic hydrogen bubble template method is reported. The lithiation/delithiation mechanism is studied in detail by both in situ and ex situ X‐ray diffraction, indicating the reversible displacement of Zn from the Cu–Zn alloy upon reaction with Li. The influence of the alloy composition on the performance of carbon‐ and binder‐free electrodes is also investigated. The optimal Cu:Zn atomic ratio is found to be 18:82, which provides impressive rate capability up to 10 A g^?1 (≈30C), and promising capacity retention upon more than 500 cycles. The high electronic conductivity provided by Cu, and the porous electrode morphology also enable superior lithium storage capability at low temperature. Cu₁₈Zn₈₂ can indeed steadily deliver ≈200 mAh g^?1 at ?20 °C, whereas an analogous commercial graphite electrode rapidly fades to only 12 mAh g^?1.