Behavior Modification: Root Hydrotropism and Hydropatterning in Peanut (Arachis hypogaea L.) Genotypes Exhibiting Transgenerational Stress Memory

The specific coupling of root architecture and physiological function clearly plays a significant role in the establishment, growth, and survival of seedlings, as roots are the main organs of water uptake. Hydrotropism and hydropatterning, which involve the directed growth towards and proliferation in pockets of increased water availability, are two rooting behaviors that seedlings may exhibit in response to heterogeneous soil water environments. Our prior results indicate that peanut seedlings from parent plants that experienced a water deficit during vegetative growth have altered root architecture under optimal soil moisture compared to seedlings from parent plants that were kept fully irrigated. These results lend evidence to the existence of transgenerational stress memory (TSM) in seedling root architecture. To further explore TSM, we sought to characterize rooting behaviors of peanut seeds from differing parent stress histories in a heterogeneous soil water environment and link this root architecture with water uptake patterns. To meet these objectives, seeds with differing TSM of peanut genotypes C7616 and TUFRunner ‘511’ were planted in rectangular root observation chambers kept at 30° from vertical in a greenhouse. Chambers were divided into three distinct sections using a physical barrier and a layer of fine sand to allow the imposition of soil water contents of 100 or 60% of the holding capacity of the growing medium. Root proliferation and growing angle were analyzed in each section over the course of 21 days to characterize hydropatterning and hydrotropism in peanut. Root water uptake patterns were coupled with architectural traits through the use of stable isotope labeling in chamber sections. This work will enable improved understanding of the effects of TSM in peanut on both root establishment and function related to early water uptake patterns. These two traits combined will elucidate important adaptive seedling characteristics that may be modified by TSM.