Date Published: July 7, 2017
Publisher: Public Library of Science
Author(s): Sen Li, Qiang Zuo, Xiaoyu Wang, Wenwen Ma, Xinxin Jin, Jianchu Shi, Alon Ben-Gal, Khawar Jabran.
Water-saving ground cover rice production systems (GCRPS) are gaining popularity in many parts of the world. We aimed to describe the characteristics of root growth, morphology, distribution, and water uptake for a GCRPS.
A traditional paddy rice production system (TPRPS) was compared with GCRPS in greenhouse and field experiments. In the greenhouse, GCRPS where root zone average soil water content was kept near saturation (GCRPSsat), field capacity (GCRPSfwc) and 80% field capacity (GCRPS80%), were evaluated. In a two-year field experiment, GCRPSsat and GCRPS80% were applied.
Similar results were found in greenhouse and field experiments. Before mid-tillering the upper soil temperature was higher for GCRPS, leading to enhanced root dry weight, length, surface area, specific root length, and smaller diameter of roots but lower water uptake rate per root length compared to TPRPS. In subsequent growth stages, the reduced soil water content under GCRPS caused that the preponderance of root growth under GCRPSsat disappeared in comparison to TPRPS. Under other GCRPS treatments (GCRPSfwc and GCRPS80%), significant limitation on root growth, bigger root diameter and higher water uptake rate per root length were found.
Discrepancies in soil water and temperature between TPRPS and GCRPS caused adjustments to root growth, morphology, distribution and function. Even though drought stress was inevitable after mid-tillering under GCRPS, especially GCRPS80%, similar or even enhanced root water uptake capacity in comparison to TPRPS might promote allocation of photosynthetic products to shoots and increase water productivity.
Rice (Oryza sativa L.) is one of the most important grain crops for more than 50% of the world’s population, accounting for approximately 20% of total energy intake, and an annual increase of 8–10 million tons is estimated necessary to meet future needs . China is the largest rice producer and consumer in the world, and the area under rice accounts for about 30% of the country’s total farmland while consuming approximately 70% of water resources directed to agriculture . Cultivation in a traditional paddy rice production system (TPRPS) is typically characterized by luxurious water consumption and low efficiency . Rapidly increasing population and global water shortage make development of water-saving rice production technologies inevitable, especially in China [4, 5].
In comparison to TPRPS, enhanced surface soil temperature before mid-tillering and limited root zone soil water content at later growth stages led to significant adjustments to the root system under GCRPS. Before mid-tillering, roots under GCRPS grew and branched faster but water uptake rates per root length were limited. The subsequent situation was completely reversed, with root growth and branching limited while water uptake rates per root length improved under GCRPS, especially GCRPS80%. The adjustments in the root system allowed plants to allocate more photosynthetic products to shoots (e.g. lower root-to-shoot ratio) and ultimately to increase yield while saving water. However, further study is required to understand the physiological mechanism for this finding.