Inherent and Stress-Induced Responses of Fine Root Morphology and Anatomy in Commercial Grapevine Rootstocks with Contrasting Drought Resistance

Abstract

Some grapevine rootstocks perform better than others during and after drought events, yet it is not clear how inherent and stress-induced differences in root morphology and anatomy along the length of fine roots are involved in these responses. Using a variety of growing conditions and plant materials, we observed significant differences in root diameter, specific root length (SRL) and root diameter distribution between two commonly used commercial grapevine rootstocks: Richter 110 (110R; drought resistant) and Millardet et de Grasset 101-14 (101-14Mgt; drought sensitive). The 110R consistently showed greater root diameters with smaller SRL and proportion of root length comprised of fine lateral roots. The 110R also exhibited significantly greater distance from tip to nearest lateral, longer white root length, and larger proportion of root length that is white under drought stress. Mapping of fine root cortical lacunae showed similar patterns between the rootstocks; mechanical failure of cortical cells was common in the maturation zone, limited near the root tip, and increased with drought stress for both genotypes; however, lacuna formed under wetter soil conditions in 110R. Results suggest that drought resistance in grapevine rootstocks is associated with thick, limitedly branched roots with a larger proportion of white-functional roots that tend to form lacuna under more mild water deficit, all of which likely favor continued resource acquisition at depth.

Physiological and Transcriptomic Evaluation of Drought Effect on Own-Rooted and Grafted Grapevine Rootstock (1103P and 101-14MGt)

“…A similar response of 1103P to drought was reported in the literature in comparison to M4 rootstock: under mild to severe water deficit 1103P reduced gs, resulting in lower E, Pn, WUE, and water potential than M4 [36]. Due to its ability to sense and avoid water stress, 1103P was generally considered to be tolerant to drought [27,28]. Nevertheless, the avoidance strategy can limit both vegetative growth and grape ripening during the drought period, due to the inhibition of carbon assimilation.…”

“…Based on the increase of arid and semi-arid conditions in several viticultural areas, the selection of new rootstocks with high water use efficiency, plant growth capacity, and scion adaptability represents an important strategy to face the negative effects of drought [21][22][23]. The rootstock genotype affects the response of the scion to drought in several ways: controlling the gas exchange and the water use efficiency at the leaf level [9,21,24,25]; determining the size and the depth of the root system, impacting water uptake during water deficit [26]; and sensing and responding to water deficit signals [27][28][29]. For example, rootstock 1103P induces stomatal closure to reduce water loss during dry periods and increases water uptake, thus growing a wider and deeper root system than rootstock 101-14MGt [26].…”

Anatomical structure interpretation of the effect of soil environment on fine root function

“…The absorption of water by the root first involves the radial water transport from the soil solution to the root column, and then flows upward into the shoot through the xylem catheter ( Ouyang et al, 2020 ). The response of fine roots to drought involves the complex relationship between anatomical structure and function ( Barrios-Masias et al, 2015 ; Reingwirtz et al, 2021 ). Studies have shown that plants in arid environments will carry out drought avoidance strategies ( Freschet et al, 2017 ).…”

Biomechanics and hydraulics of Opuntia ficus-indica roots exposed to extreme drought

“…One of the most evident changes is the increase in suberization in cell layers outside the stele (e.g., pericycle and cortex; North and Nobel, 1991;Karahara et al, 2004), that increase the hydraulic resistance within roots, negatively affecting water storage (i.e., capacitance) that is necessary to endure under extreme drought periods (Niklas, 1992;Kramer and Boyer, 1995). Root hydraulic conductivity (Lp r ) decreases both by the reduction of cell walls permeability caused by suberization, but also by cell wall mechanical failure known as cortical lacunae, hydraulically disconnecting the water flow at the soil-root interface (Zimmermann, 1983;North and Nobel, 1992;Cuneo et al, 2016;Cuneo et al, 2021).…”