Rice root growth and physiological responses to SRI water management and implications for crop productivity

Abstract

This paper reports on several research findings on rice root responses, in terms of growth and physiology, manifested when applying System of Rice Intensification water management principles under semi-field and field conditions, in conjunction with variations in plant density and microbial density in the soil. The research aimed to learn about causal relationships, if any, between rice root and shoot growth at different growth stages of the rice plant's development and their cumulative effect on yield, which is affected by both biotic and abiotic influences. It was seen that greater root length density and a higher rate of root activity affected the yield-contributing parameters in all of the trials, whether conducted under semi-field or field conditions. At the same time, both root parameters were significantly affected by the water regime, soil microbial density, and planting pattern, the three main factors considered. The most important finding observed under semi-field conditions was that enhanced microbial density in the soil improved the sink capacity of the rice plants under all water regimes evaluated. Positive correlations were found between the chlorophyll content of the flag leaf and the duration of grain filling, between the chlorophyll content of plants' lower leaves and their roots' oxidizing activity rate, and the roots' oxidizing activity rate at later growth stage and the available soil nitrogen. These relationships can significantly improve rice plants' physiological efficiency and hence grain yield, provided that soil nutrients are not a limiting factor and when source-sink demand is maintained simultaneously. To realize the highest crop yield per hectare, both planting pattern and spacing are factors that need to be optimized. This paper in its conclusion considers the relevance of exploiting roots' potential for plasticity to enhance crop productivity in the context of impending water constraints and climate-change effects.

Physiological responses of crop plants against Trichoderma harzianum in saline environment

“…There was a maximum amount of photosynthetic pigments present in Th-treated plants in maize and rice crops as compared to untreated plants under NaCl condition. Further, these results are in accordance with the results of Mishra and Salokhe (2011) who reported that inoculation of seed by Trichoderma enhanced pigment system PSII performance and produced a higher rate of transpiration in plants under salt stress conditions. In plants subjected to salinity stress, photosynthetic rate and stomatal conductance might be disturbed due to the higher amount of Na + ions accumulation which disturb the electron transport chain during photosynthesis (Kanwal et al 2011).…”

Review of SRI modifications in rice crop and water management and research issues for making further improvements in agricultural and water productivity

“…The trials reported by Mishra and Salokhe (2011) showed the importance of maintaining sufficient water available in the soil for plants during their reproductive phase. Some SRI practitioners, however, have reported good results from extending alternate wetting and drying (AWD) throughout the whole crop cycle (see also ).…”

“…An additional important benefit of aerobic soil conditions is the development of larger root systems, as reported by Barison and Uphoff (2011), Mishra and Salokhe (2011) and Thakur et al (2011). This gives rice plants larger exploitable root zones in the soil, which under anaerobic conditions are further restricted by the hard pan needed to hold water for maintaining flooding.…”

Induction of water stress tolerance of mustard plants using Trichoderma as biological seed treatment

“…Drought tolerance in mustard plants using Trichoderma is justified by the fact that enhanced rooting provides increased surface area for absorption and long roots penetrate deeper in soil which can absorb the deep seated water and increase plant stand in water stress conditions. In addition of biocontrol ability of Trichoderma spp., the activity that contributes to the enhancement of root growth and distribution was also considered as a key factor to the prolonged photosynthetic activity and the delayed senescence in rice plants (Mishra and Salokhe, 2011). Ghahfarokhy et al (2011) reported that colonization of roots with VAM fungi and Trichoderma spp.…”