Abstract
Drought leads to greater yield loss in crops than any other abiotic stress. Roots form a plant’s first line of defense against water deficit, and in this issue Gao and Lynch (pages 4533–4546) report that fewer but longer crown roots facilitate water acquisition from subsoil and thus improve drought tolerance in maize. Roots are the first organ to sense water deficit, and at the same time they extract virtually all those mineral nutrients from soil that are consumed by humans. Soil resource acquisition under challenging conditions such as drought is a primary limitation on plant productivity, resulting in low yields and thus food insecurity in the poorest countries. Indeed, in overall global agriculture, drought accounts for more loss in plant productivity than any other abiotic factor. Thus the development of crop cultivars with enhanced traits for soil resource acquisition is a key goal for feeding the growing world population (Lynch, 2007). However, so far the potential of root traits for crop improvement remains largely unexploited, largely because of the limited accessibility of roots in their belowground soil habitat.
Highlights
Untapping root system architecture for crop improvementDrought leads to greater yield loss in crops than any other abiotic stress. Roots form a plant’s first line of defense against water deficit, and in this issue Gao and Lynch (pages 4533–4546) report that fewer but longer crown roots facilitate water acquisition from subsoil and improve drought tolerance in maize
Elongation (Xu et al, 2015)
Anatomical and physiological experiments have been conducted to define hypothetical maize ideotypes optimized for resource acquisition
Summary
Drought leads to greater yield loss in crops than any other abiotic stress. Roots form a plant’s first line of defense against water deficit, and in this issue Gao and Lynch (pages 4533–4546) report that fewer but longer crown roots facilitate water acquisition from subsoil and improve drought tolerance in maize. Soil resource acquisition under challenging conditions such as drought is a primary limitation on plant productivity, resulting in low yields and food insecurity in the poorest countries. Elongation (Xu et al, 2015) Both genes encode LOB-domain proteins, which belong to a wider family whose members act as central regulators of auxin signal transduction (Taramino et al, 2007). While these genes are master regulators for the initiation and elongation of individual shoot-borne roots, the number of these roots is highly variable and ranges from five to >70 (see references in Gao and Lynch, 2016) between different genotypes, suggesting that the overall total is controlled by multiple genes. ‘Steep’ and ‘deep’ refer to morphological adjustments by steep root-growth angles and extended elongation of shootborne roots to access water in deeper soil layers; ‘cheap’ refers to cellular adjustments to reduce the metabolic costs of soil exploration, such as a decreased number of cortical cell files, increased cortical cell size and the formation of root cortical aerenchyma (Lynch, 2015)
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