Suresh K. Sinha

Effects of climate change on rice production in the tropical humid climate of Kerala, India.

The CERES-Rice v3. crop simulation model, calibrated and validated for its suitability to simulate rice production in the tropical humid climate Kerala State of India, is used for analysing the effect of climate change on rice productivity in the state. The plausible climate change scenario for the Indian subcontinent as expected by the middle of the next century, taking into account the projected emissions of greenhouse gases and sulphate aerosols, in a coupled atmosphere-ocean model experiment performed at Deutsches Klimarechenzentrum, Germany, is adopted for the study. The adopted scenario represented an increase in monsoon seasonal mean surface temperature of the order of about 1.5°C, and an increase in rainfall of the order of 2 mm per day, over the state of Kerala in the decade 2040–2049 with respect to the 1980s. The IPCC Business-as-usual scenario projection of plant usable concentration of CO2 about 460 PPM by the middle of the next century are also used in the crop model simulation. On an average over the state with the climate change scenario studied, the rice maturity period is projected to shorten by 8% and yield increase by 12%. When temperature elevations only are taken into consideration, the crop simulations show a decrease of 8% in crop maturity period and 6% in yield. This shows that the increase in yield due to fertilisation effect of elevated CO2 and increased rainfall over the state as projected in the climate change scenario nearly makes up for the negative impact on rice yield due to temperature rise. The sensitivity experiments of the rice model to CO2 concentration changes indicated that over the state, an increase in CO2 concentration leads to yield increase due to its fertilisation effect and also enhance the water use efficiency of the paddy. The temperature sensitivity experiments have shown that for a positive change in temperature up to 5°C, there is a continuous decline in the yield. For every one degree increment the decline in yield is about 6%. Also, in another experiment it is observed that the physiological effect of ambient CO2 at 425 ppm concentration compensated for the yield losses due to increase in temperature up to 2°C. Rainfall sensitivity experiments have shown that increase in rice yield due to increase in rainfall above the observed values is near exponential. But decrease in rainfall results in yield loss at a constant rate of about 8% per 2 mm/day, up to about 16 mm/day.

Physiological, Biochemical, and Genetic Basis of Heterosis

Publisher Summary This chapter describes the basic mechanism of heterosis, along with the physiological and genetic basis for this phenomenon. Heterosis is a phenomenon through which the yields of crop plants can be improved and explains the way this mechanism can be exploited more effectively and profitably. Heterosis in plants has usually been identified with hybrid vigor as a major component. Hybrid vigor is defined as the heterosis manifest, and is thus the phenotypic expression of heterosis, which is a genetic phenomenon. Heterosis can be obtained in plants, animals, and microorganisms for various economically important characters. In plants, the phenomenon is common both in cross as well as in self-pollinated crops. The crops in which heterosis has been commercially exploited or will be exploited in the near future are listed. The chapter discusses the heterosis in heterotrophs and autotrophs along with the various theories of heterosis: (1) dominance hypothesis, (2) overdominance hypothesis, (3) physiological stimulus and initial capital, (3) complementation at cellular and subcellular level, (4) balanced metabolism, and (5) hormonal and other factors.

Methane emissions from rice fields amended with biogas slurry and farm yard manure

In an experiment on methane-emission measurements from rice fields amended with urea, biogas spent slurry (BSS) + urea, and farm yard manure (FYM) + urea, three distinctive peaks in the methane emissions were observed at 15, 46, and 69 days after transplanting (DAT) due to the availability of readily degradable C-sources. In all cases, the highest peak was at 69 DAT. The steepest Eh drop to a minimum of -320 mV was reached within two weeks of submergence. pH ranged between 7.5 and 8.5. The combined fertilization (FYM + urea) plot showed the maximum emission rate of 4.86 mg m−2 h−1 with a total load of 49.44 kg ha−1 and was 2.3 times higher than (BSS + urea)-treated plot (22.08 kg ha−1). Grain yields in urea, (BSS + urea) and (FYM + urea) plots were 3.34, 2.94, and 2.85 t ha−1 respectively, suggesting that biogas slurry is a preferred source over FYM causing lesser environmental pollution without any significant reduction in grain yield.

Deforestation, Climate Change and Sustainable Nutrition Security: A Case Study of India

Wheat and rice are the most important crops from the point of view of maintaining a sustainable nutrition security system for India, a country whose population may reach one billion by the year 2000. The implications of climate change deriving from tropical deforestation, particularly as concerns temperature and precipitation, with reference to the yield of wheat and rice in different parts of India are hence being studied carefully. Any possible positive gain arising from increased CO2 concentration is likely to be offset by the yield decline induced by higher temperature and shorter growing period.

Analyzing the limitations set by climatic factors, genotype, water and nitrogen availability on productivity of wheat I. The model description, parametrization and validation

Abstract A mechanistic crop growth simulation model, wtgrows , is developed for use in analyzing effects of climatic variables and crop management on productivity of wheat in tropical and sub-tropical wheat regions of India. The model, written in csmp and fse , simulates daily dry matter production as a function of radiation and temperature, and water and nitrogen availability. Crop aspects of the model are arranged in submodels covering development, photosynthesis, respiration, carbohydrate partitioning, dry matter production, leaf area, grain growth and transpiration. A soil water balance model is attached to simulate water uptake and to determine water stress. Another submodel determines nitrogen uptake, distribution and N stress. Water and nitrogen stresses, depending upon their severity, affect various physiological processes. The model requires inputs relating to site, daily weather, soil physical characteristics and crop management. Switches allow water and/or nitrogen stresses to be terminated to establish climatically determined potential grain yield. Various aspects of the model were validated using a large number of independent experiments. Comparison of simulated and measured quantities indicated satisfactory performance of the model in reference to water and nitrogen uptake, dry matter growth and grain yield in potential as well as Water- and N-limited environments. The model appears useful as a tool for optimizing use of water and nitrogen.

Performance of wheat and triticale cultivars in a variable soil—water environment II. Evapotranspiration, water use efficiency, harvest index and grain yield

Abstract This communication, based on a 3-year field study, describes the drought susceptibility of 17 cultivars of wheat and triticale, expressed in terms of grain yield, harvest index, pre- and post-anthesis evapotranspiration (ET) and water use efficiency (WUE). At the time of sowing, the available water (between−0.02 MPa and −1.5 MPa) in the soil profile varied between 12.7 and 17.6 cm depending upon the year. A large proportion of this water was consumed by the plants before anthesis, in the unirrigated treatment, leaving on average only 4.2 cm water in the initial 150-cm soil profile. However, precipitation in the post-anthesis phase increased the amount of available water. At crop maturity the soil profile had almost no available water. There were no differences in ET or WUE among the varieties studied. Grain yield and harvest index increased with increase in ET up to a certain level. Whereas the proportion of water used in the post-anthesis phase was important in irrigated plants, both pre- and post-anthesis water use were important in unirrigated wheat. Increase in ET decreased WUE but increased the harvest index. No relationship could be deduced between drought susceptibility and pre- and post-anthesis water use.

Cyanide-resistant respiration is involved in temperature rise in ripening mangoes.

Thermogenesis is attributed to the cyanide resistant respiration in the inflorescence of Arum lilies. Although cyanide resistant respiration is ubiquitously operative in the plant systems, it has never been correlated with thermogenesis except for the above example. Internal temperature of the ripening mango increased from 29.0 degrees C to 38.9 degrees C during its ripening process. Concomitantly, it was coupled with the increase in total respiration and cyanide resistant respiration as well. Implication of cyanide resistant respiration in thermogenesis has been discussed in relation to the ripening fruit.

A comparison of physiological and yield characters in old and new wheat varieties

The Indian subcontinent has witnessed a spectacular improvement in yield of wheat during the past decade (Rao, 1978). This is reflected in the improvement of the average national yields as well as of those regions where wheat is grown as an irrigated crop (Sinha & Aggarwal, 1981). However, after the release of the double dwarf variety Kalyansona, only marginal improvement in yield has occurred in recent years. Despite this, the semi-dwarf character continues to be considered a major factor for improvement of wheat. Asana & Chattopadhyay (1970), Konar & Asana (1975), and Wattal & Asana (1976) observed no significant difference in yield between tall and semi-dwarf (medium tall) varieties in pot culture experiments where lodging was prevented and competition was partly reduced. They ascribed prevention from lodging and improvement in the ratio of grain to total above-ground dry matter as major advantages in the modern varieties. Somewhat similar conclusions have recently been drawn by Austin et al. (1980). However, a detailed comparison of various physiological and biochemical characters lias not been made to determine whether any advance has occurred in basic processes such as photosynthesis and nitrogen assimilation. The present study was an effort in this direction.

Change in the predominance from C4 to C3 pathway following anthesis in Sorghum

Abstract Sorghum and Pennisetum species are known to have predominantly C4 pathway. This pathway is associated with several other characteristics. These conclusions are based on studies confined largely to seedlings. A developmental study of PEP carboxylase and RuDP carboxylase in Sorghum bicolor and Pennisetum typhoides confirmed in seedlings the predominance of PEP carboxylase, high malate: 3-phorophoglycerate ratio and ‘Krantz’ anatomy. However, after flowering, RuDP carboxylase was predominant in the leaves of both Sorghum and Pennisetum. This observation was associated with higher 3-phosphoglycerate:malate ratio following 14CO2 fixation. The anatomy of the leaf remained unchanged and so was the chlorophyll a:b ratio. This change in system coincided with a slight fall in mean daily temperature. But in wheat RuDP carboxylase remained the predominant enzyme in spite of the rising mean daily temperature. Therefore, the change from C4 to C3 appears to be related more to the developmental stages.

Performance of wheat and triticale cultivars in a variable soil—water environment I. Grain yield stability

Seventeen cultivars of Triticum aestivum, T. durum and triticale were grown for 5 years in irrigated and unirrigated conditions to investigate yield stability and its association with various morpho-physiological characters. Differences in rainfall and irrigation provided environments with variable water availability. Grain yield of all cultivars was reduced by drought stress and cultivars differed in their yield stability. The drought susceptibility index (S) was positively related to the regression slope of mean grain yield (Y) on the environmental index (X). On an average, T. aestivum cultivars were more drought resistant than triticales. Cultivars of T. durum were most drought susceptible. The drought resistance was not always associated with plant height. Cultivars were classified into four groups based on their yield potential and drought resistance.