Global warming will increase root heat stress, which is already common under certain conditions. Effects of heat stress on root nutrient uptake have rarely been examined in intact plants, but the limited results indicate that heat stress will decrease it; no studies have examined heat-stress effects on the concentration of nutrient-uptake proteins. We grew Solanum lycopersicum (tomato) at 25 °C/20 °C (day/night) and then transferred some plants for six days to 35 °C /30 °C (moderate heat) or 42 °C/37 °C (severe heat) (maximum root temperature = 32 °C or 39 °C, respectively); plants were then moved back to control conditions for seven days to monitor recovery. In a second experiment, plants were grown for 15 days at 28 °C/23 °C, 32 °C/27 °C, 36 °C/31 °C, and 40 °C/35 °C (day/night). Concentrations of nutrient-uptake and -assimilation proteins in roots were determined using protein-specific antibodies and ELISA (enzyme-linked immunosorbent assay). In general, (1) roots were affected by heat more than shoots, as indicated by decreased root:shoot mass ratio, shoot vs. root %N and C, and the level of nutrient metabolism proteins vs. less sensitive photosynthesis and stomatal conductance; and (2) negative effects on roots were large and slow-to-recover only with severe heat stress (40 °C–42 °C). Thus, short-term heat stress, if severe, can decrease total protein concentration and levels of nutrient-uptake and -assimilation proteins in roots. Hence, increases in heat stress with global warming may decrease crop production, as well as nutritional quality, partly via effects on root nutrient relations.

As with above-ground tissues, plant roots can be subjected to stressful high temperatures that can limit whole-plant function and decrease crop productivity. Further, with impending climate change, the frequency, duration, and severity of root heat stress will increase. In comparison to shoot function, especially photosynthesis, much less is known regarding heat stress and roots. Most previous research on roots and heat stress has been conducted on detached roots or by heating only roots or parts of root systems (but not shoots too) in intact herbaceous plants, and most past studies on intact plants have imposed chronic heat stress, with few examining effects of abrupt heat stress (e.g., heat waves). Importantly, plant responses to heat stress often differ in detached roots or when only roots are heated, compared to plants wherein both shoots and roots (or shoots only) are heated, and responses to chronic and abrupt heat stress can differ. Hence, many past results do not inform as to how natural heat stress often impacts roots in intact plants or do not inform as to the effects of heat waves on roots. Both chronic and abrupt heat stress can decrease root growth and function, including nutrient and water uptake, and studies in which both roots and shoots were heat-stressed indicate that roots are often more sensitive to heat stress than shoots. Heat stress may affect roots both directly and indirectly, and indirect effects likely involve decreases in shoot carbon provided to roots or changes in root water relations driven by increased shoot water demand, which then affect root growth and nutrient uptake. Interactive effects between heat stress and other global environmental change factors (e.g., elevated carbon dioxide, drought) on roots are likely. We conclude that further research on roots and heat stress is strongly warranted.

Rising global CO 2 levels are a major factor that impacts not only the environment but also many plant functions including growth, productivity and nutritional quality. The study examined the impact of elevated [CO 2 ] on nutritional quality and growth characteristics of lettuce (Lactuca sativa) and spinach (Spinacia oleracea). Elevated [CO 2 ] decreased the concentration of many important nutrients including nitrogen (protein), potassium and phosphorus in the edible parts of both lettuce and spinach. The nitrogen concentration in lettuce shoots was reduced by more than 30% at elevated [CO 2 ] compared to the plants grown at ambient level of CO 2 . Similarly the concentration of a number of micronutrients including sulfur, zinc, copper and magnesium, was depressed in lettuce shoots. Although the total phenolic content and antioxidant capacity were higher in lettuce at elevated CO 2 , they were not affected in spinach. The photosynthetic activity was variable among the plant species while there was no increase in the carbon accumulation in these plants at elevated [CO 2 ]. However, there was significant reduction in the leaf stomatal conductance in both lettuce and spinach in response to higher [CO 2 ], which is likely affect both water loss from the leaves and their photosynthetic activity. The results indicate a broad adverse impact of rising [CO 2 ] on the nutritional quality of commonly consumed leafy vegetables namely, lettuce and spinach.

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The experiment was conducted with four levels of nitrogen (40, 80,120 and 160 kg/ha) and 3 different cultivars (Prithivi hybrid), Masuli (HYV) and Sunaulo Sugandha (Aromatic).RMSE value (747.35 kg/ha, 1.106 days, 2.58 days and 0.004 kg/ha) and D-stat value (0.793, 0.99, 0.99 and 0.633) for grain yield, anthesis days, maturity days, and individual grain weight respectively. The objective of this study was to identify whether CSM-CERES-Rice model can be used in Nepalese condition and to evaluate the sensitivity of model with impact of climate change on rice production. Eight different climate scenarios were built by perturbing maximum and minimum temperature (± 4°C), CO2 (± 20ppm), solar radiation (±1MJ/m2/day) using interactive sensitivity analysis mode in DSSAT. Among the scenario evaluated, temperature (± 40°C), CO2 concentration (+20 ppm) with change in solar radiation (±1MJ m-2 day-1) resulted maximum increase in yield (by 62, 41 and 42%) under decreasing climatic scenarios and sharp decline in yield (by 80, 46 and 40%) was observed under increasing climate change scenarios, in Prithivi, Masuli and Sunaulo Sugandha cultivars respectively.Not surprisingly, increasing yield by (48, 25 and 27 %) and decrease in yield by(77, 41 and 34) by perturbing only maximum and minimum temperature by (± 4) shows that the temperature is most sensitive for yield potentiality of cultivars than other. CERES-Riceversion 4.0 was well calibrated in Chitwan Nepal condition. The model applications show that model could be a tool for precision decision-making. There was variation in yield in response to the change in climatic scenario in the study. RMSE value (747.4 kg/ha, 1.11days, and 2.58 days), and d-stat (0.79, 0.99 and 0.99) for grain yield, anthesis, and maturity days confirm the possibility of CERESRiceuse in Nepalese agriculture. The finding showed that there was sharp decrease in rice yield due to change in temperature, CO2 and solar radiation. Climatic scenario developed by CERES-Rice model in sensitivity analysis resulted yield reduction up to 80%. Among the cultivar, hybrid rice shows more vulnerability with climate change. Decrease in yield were mainly associated with lowering growth duration along with increasing temperature, where as there is very less counter effect of increasing carbon dioxide concentration and solar radiation. Agronomy Journal of Nepal (Agron JN) Vol. 3. 2013, Page 11-22 DOI: http://dx.doi.org/10.3126/ajn.v3i0.8982

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Oxygen limiting conditions are a common occurrence in root zones of most crop plants and can adversely affect nearly all aspects of plant growth and development including its survival. The objective of this study was to determine the effectiveness of a novel redox cycling agent, vitamin K 3 , and various peroxides including hydrogen peroxide, calcium peroxide and magnesium peroxide in alleviating the effects of hypoxia in bean seedlings grown in nutrient culture. All the anti-hypoxic agents including vitamin K 3 had a positive impact on the overall growth of bean seedlings under hypoxic conditions, but their responses were variable depending on the concentration. With regard to shoot growth, vitamin K 3 (5 μM) increased the leaf area significantly, by more than 58% over the hypoxic control plants and produced the highest stem fresh weight similar to calcium peroxide (20 μM) and magnesium peroxide (10 μM). In addition, the use of vitamin K 3 resulted in the highest accumulation of chlorophyll (chla + chlb) in the leaves, an increase of nearly two-fold over the hypoxic control plants. Furthermore under hypoxia, calcium peroxide (20 μM) and magnesium peroxide (10 μM) produced the highest leaf biomass (FW) followed by vitamin K 3 . Vitamin K 3 (1 μM) also favored root growth in bean seedlings under hypoxia; it produced the largest increase in root length and root biomass (DW) similar to calcium peroxide and magnesium peroxide. Based on the overall shoot and root growth response of bean seedlings to various anti-hypoxic substances under hypoxic conditions, calcium peroxide, magnesium peroxide and vitamin K 3 performed better than hydrogen peroxide. These findings show that vitamin K 3 and peroxide salts are * Corresponding author. C. B. Rajashekar et al. 3397 effective in alleviating hypoxic stress in bean seedlings and also, further highlight their potential for dealing with hypoxia in wide ranging situations.

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