No abstract

Drought severely limits crop yield of peanut. Yet cultivars with enhanced root development enable the exploration of a greater volume of soil for water and nutrients, helping the plant survive. Root distribution patterns of three genotypes (ICGV 98305, ICGV 98324 and Tifton‐8) were compared when grown in well‐watered rhizoboxes and when grown in rhizoboxes where an early‐season drought was imposed using rain‐exclusion shelters. The treatments were arranged in a completely randomized design with three replications, and the experiment was conducted during two seasons at the Field Crop Research Station of Khon Kaen University, in Khon Kaen, Thailand. The root system of ICGV 98305, when grown under drought, had a significantly higher root length in the 30–110 cm deep soil layers and less roots in the 0–30 cm soil layers when under drought than when grown under well‐watered conditions. Roots of Tifton‐8 had the largest reductions in root length in upper soil layer and reduced in most soil layers. Tifton‐8 grown under drought was smaller than under well‐watered control for all root traits, showing negative response to drought. The peanut genotypes with high root traits in deeper soil layer under early‐season drought might contribute to drought avoidance mechanism.

No abstract

Changes in the anatomical structure of peanut roots due to early season drought will likely affect the water acquiring capacity of the root system. Yet, as important as these changes are likely to be in conferring drought resistance, they have not been thoroughly investigated. The objective of this study was to investigate the effects of different durations of drought on the root anatomy of peanut in response to early season drought. Plants of peanut genotype ICGV 98305 were grown in rhizoboxes with an internal dimension of 50 cm in width, 10 cm in thickness and 120 cm in height. Fourteen days after emergence, water was withheld for periods of 0, 7, 14 or 21 days. After these drought periods, the first and second order roots from 0–20 cm below soil surface were sampled for anatomical observation. The mean xylem vessel diameter of first- order lateral roots was higher than that of second- order lateral roots. Under early season drought stress root anatomy changes were more pronounced in the longer drought period treatments. Twenty-one days after imposing water stress, the drought treatment and irrigated treatment were clearly different in diameter, number and area of xylem vessels of first- and second-order lateral roots. Plants under drought conditions had a smaller diameter and area of xylem vessels than did the plants under irrigated control. The ability of plants to change root anatomy likely improves water uptake and transport and this may be an important mechanism for drought tolerance. The information will be useful for the selection of drought durations for evaluation of root anatomy related to drought resistance and the selection of key traits for drought resistance.

Root morphology and anatomy are important plant traits that could potentially influence seedling vigour, resource acquisition and susceptibility to early‐season stress. Therefore, the objective of the current experiment was to evaluate the effects of cultivar and growth temperature on seedling root growth and anatomical characteristics in cotton. To address this objective, experiments were conducted with six modern cotton cultivars, expected to have differences in seedling vigour, grown under optimal (30/20°C) and suboptimal (20/15°C) day/night temperature regimes. Root morphology and taproot cross‐sectional anatomy were evaluated two weeks after planting. Cultivars with the most vigorously growing root systems produced 73% more secondary roots, 68% more total root length, 74% more surface area and 72% higher total root volume than the least vigorous cultivars. The cultivar with the greatest production of secondary roots also exhibited a somewhat uncommon hexarch arrangement of vascular bundles in taproot cross sections. Thus, we suggest that this difference in root anatomy may be a determinant of genotypic differences in lateral root development. In response to low temperature, taproot length, total root length, secondary root formation, root surface area and root volume declined substantially relative to optimal temperature conditions (35%–75% declines). This reinforces the need to ensure optimal temperature conditions at planting or to identify cultivars with improved performance under suboptimal early‐season conditions. Conversely, root diameter responded positively to low growth temperatures, and cold‐induced increases in root thickness were associated with increases in the number and cross‐sectional area of root cells.