Wheat (Triticum aestivum L.) cvs. HD 2285 (relatively tolerant) and WH 542 (susceptible) were exposed to ambient and elevated temperature (3 -4 °C higher) in open top chambers during post anthesis period. The grain yield components were determined at the time of maturity. In order to elucidate the basis of differential tolerance of these cultivars, the excised developing grains (20 d after anthesis) of ambient grown plants were incubated at 15, 25, 35 and 45 °C for 2 h and then analysed for the activities of soluble starch synthase (SSS), granule bound starch synthase (GBSS), kinetic parameters of SSS and content of heat shock protein (HSP 100). The elevated temperature during grain development significantly decreased grain growth in WH 542 whereas no such decrease was observed in HD 2285. High temperature tolerance of HD 2285 was found to be associated with higher catalytic efficiency (V max /K m ) of SSS at elevated temperature and higher content of HSP 100.

In order to meet the ever rising global demand for natural rubber, cultivation of Hevea is being extended to nontraditional regions of India where extreme climatic conditions like drought and low temperature negatively influence the crop performance. In order to ensure maximum productivity, identification of drought tolerant clones of Hevea which can cope up with stress and give better crop yield is essential. Several attempts have been made previously to identify genes that are associated with drought tolerance in Hevea. In the present study, quantitative expression analysis was made using quantitative PCR for seven drought associated transcripts in four clones of Hevea with varying levels of drought tolerance. Among the seven genes studied, Mitogen Activated Protein (MAP) kinase, Myeloblastosis (Myb) transcription factor, C-repeat responsive element/Dehydration Responsive Element (CRT/DRE) binding factor and Nuclear Factor Y subunit A (NFYA) showed a positive association with drought tolerance. Transcripts of ascorbate peroxidase and heat shock protein 70 (HSP 70) did not show any correlation with drought tolerance. Interestingly, catalase gene was found down regulated in all the clones under drought condition. The possible role of these genes based on their level of gene expression in four different clones of Hevea with varying levels of drought tolerance is discussed.

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Wheat (Triticum aestivum L.) cvs DL 153‐2 and HD 2285 (relatively tolerant), HD 2329 and WH 542 (relatively susceptible), were grown under normal (27 November) and late (28 December) sown conditions. In another experiment, these cultivars were grown under normal sowing and at anthesis stage, they were transferred to control (C) and heated (H) open top chambers (OTCs). Under late sowing, wheat cultivars were exposed to a mean maximum temperature of up to 3.6 °C higher than normal sowing and in H‐OTCs, mean maximum temperature was 3.2 °C higher than C‐OTCs during grain growth period. Heat susceptibility index (S) for grain growth and grain yield was determined at maturity in both the experiments. The level of heat shock protein (HSP 18) in the developing grains was determined in C‐ and H‐OTC grown plants and in normal and late sown plants by Western blot analysis. The moderately high temperature exposure increased the accumulation of HSP 18 in the developing grains. The relatively tolerant cultivars, as also revealed from S, showed a greater increase in HSP 18 compared with susceptible types in response to moderate heat stress. An association of HSP 18 with thermotolerance for grain growth in wheat was indicated.

<div><table cellspacing="0" cellpadding="0" align="center"><tbody><tr><td align="left" valign="top"><p>The physiology of   root trainer plants in comparison to polybag plants of two popular <em>Hevea </em>clones,   RRII 105 and RRII 430 was studied. Dry matter partitioning and physiological   parameters like leaf water potential, relative water content, chlorophyll   content, PS II activity and photosynthetic efficiency were studied in root   trainer and polybag plants and compared. Root trainer plants had only 55 per   cent less biomass than polybag plants at two whorled stage. No variation was   noticed in water relations among the poly bag and root trainer plants. Total   chlorophyll content and chlorophyll <em>a/b </em>ratio were higher in polybag   plants than root trainer plants of both clones. Polybag plants showed higher   light saturation point when gas exchange was measured at different   photosynthetic photon flux densities. Though there was no variation in   effective quantum yield (Φ PSII), the root trainer plants of RRII 105 showed   more excess electrons (J*) at higher light intensities. Photosystem II   activity and photosynthetic carbon assimilation rates were less in root   trainer plants under open and shaded conditions. The results indicated that   the root confinement in root trainer plants has significant effect on the   physiology of plants. The reduction in plant biomass and other physiological   traits in root trainer plants can be attributed to the limited space in the   container, limiting further root growth, which otherwise is beneficial for   giving a priming effect as long as the plant remains in the container.   Further studies are needed to quantify this ‘stress factor’ in root trainer   plants and its implications in growth and establishment of plants in the   field.</p></td></tr></tbody></table></div>