Abstract
ABSTRACTThe root system architecture (RSA) has been reported to be determined by several root traits such as branching, elongation, and growth angle. This study aimed to evaluate the genotypic variation of plasticity in RSA in response to different soil water distributions in a soil profile. IR64 (shallow root system), YTH183 (adapted to rainfed lowland conditions due to high plasticity in root elongation), and Kinandang Patong (KP – deep root system) were grown in PVC root boxes for 34 days under continuously waterlogged conditions and with soil moisture fluctuations (SMF). For SMF, watering was done from the top of the root box (TI-SMF) or from the bottom of the root box (BI-SMF). A water gradient was observed more clearly in BI-SMF than in TI-SMF, while mean soil moisture content in the root box was kept at around 23% (v/v) after first irrigation in both SMF treatments. RSA changed drastically with SMF in all cultivars, all of which tended to shift root distribution to deeper soil layers in response to SMF. Such changes in RSA resulted from different degrees of plasticity exhibited mainly in nodal root and L-type lateral root development. YTH183 showed a greater ability to change its root growth angle and thus its root distribution in the deeper soil layer compared to IR64 and KP under SMF, indicating that YTH183 could help to improve RSA in cultivars adapted to SMF.
Highlights
Soil water is rarely constant but changeable as a result of rainfall, watering and water uptake by plants
To evaluate the Root system architecture (RSA), we focused on three rice cultivars; IR64, YTH183, and Kinandang Patong (KP), which have different RSAs
The seedlings were first grown under 20% (w/w) soil moisture contents (SMC) and the seedlings were thinned to one seedling per box at 5 days after sowing (DAS)
Summary
Soil water is rarely constant but changeable as a result of rainfall, watering and water uptake by plants. Understanding root development in response to soil moisture heterogeneity is important for maintaining plant growth under water-stressed conditions, which is a major limiting factor for plant growth. Root system architecture (RSA) is spatially affected by soil water distribution. The position of water supply in soil profile may affect the soil water distribution, and RSA and plant growth (Kono et al, 1987a). Water is supplied from the soil surface by rainfall and irrigation. In the case of a rice ecosystem that is distributed on a toposequence such as a slope hill, water is supplied from the subsoil through groundwater as well as from the topsoil (Boling et al, 2008)
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