BayCEER Workshop 2019

The effect of maize root hairs on transpiration and leaf water potential during soil and atmospheric drying

Limited water supply is one of the largest impediments to food production worldwide. Therefore, improving crops management of soil water depletion will be important to sustain the increasing food demand. Maize is the world’s most important crop and appropriate for food production in semi-arid regions with low-input agriculture. Hence, exploring its root functionality will provide valuable knowledge about the potential to use maize with different root and rhizosphere traits in crop improvement programs. The overall objective of this study was to investigate the role of root hairs for soil-plant water relations in drying soils. Although the importance of root hairs in the uptake of immobile elements is well accepted, their role in water uptake remains controversial. We hypothesize that root hairs improve plant resistance to drought stress, as: 1) root hairs are able to transport water; 2) they maintain the continuity of the water flow at the root-soil interface and thus, 3) they facilitate plant root water uptake, especially in dry soil. We tested the emerging role of root hairs on two plant-scale variables: transpiration and leaf water potential. We compared maize (Zea mays L.) plants with (rth3 wild-type) and without root hairs (rth3-mutant) in three different soils (Alfisol, Vertisol and Sandy Soil). We studied whether and in what conditions there are differences between genotypes, or whether there are compensation mechanisms (i.e. high root length or stomatal conductance) by the mutant to overcome the lack of root hairs. Transpiration response was monitored in two experiments under conditions of atmospheric drying as well as under conditions of soil drying. The hairless mutant has shown a higher transpiration in wet soils but declined transpiration earlier in drying soils as compared to the wild-type. Under well-watered conditions, both genotypes had the highest transpiration rates in Vertisol. In Vertisol, both genotypes closed their stomata at higher water contents.