Differences in grapevine rootstock sensitivity and recovery from drought are linked to fine root cortical lacunae and root tip function

Abstract

Structural changes during severe drought stress greatly modify the hydraulic properties of fine roots. Yet, the physiological basis behind the restoration of fine root water uptake capacity during water recovery remains unknown. Using neutron radiography (NR), X-ray micro-computed tomography (micro-CT), fluorescence microscopy, and fine root hydraulic conductivity measurements (Lp r), we examined how drought-induced changes in anatomy and hydraulic properties of contrasting grapevine rootstocks are coupled with fine root growth dynamics during drought and return of soil moisture. Lacunae formation in drought-stressed fine roots was associated with a significant decrease in fine root Lp r for both rootstocks. However, lacunae formation occurred under milder stress in the drought-resistant rootstock, 110R. Suberin was deposited at an earlier developmental stage in fine roots of 101-14Mgt (i.e. drought susceptible), probably limiting cortical lacunae formation during mild stress. During recovery, we found that only 110R fine roots showed rapid re-establishment of elongation and water uptake capacity and we found that soil water status surrounding root tips differed between rootstocks as imaged with NR. These data suggest that drought resistance in grapevine rootstocks is associated with rapid re-establishment of growth and Lp r near the root tip upon re-watering by limiting competing sites along the root cylinder.

Drought‐induced lacuna formation in the stem causes hydraulic conductance to decline before xylem embolism in Selaginella

“…We suggest that the formation of this airfilled lacuna during dehydration is the primary cause for the 80% reduction in K shoot before the onset of embolism in these two species of Selaginella. This is similar to the separation and collapse of the cortex in Vitis roots leading to substantial declines in root hydraulic conductance in the early stages of drought (Cuneo et al, 2016(Cuneo et al, , 2020. We also suggest that the limited connection through trabeculae between the vasculature and the cortical tissues probably accounts for the observed lack of complete decline in K shoot until embolism formation.…”

“…The difference in K shoot between both species corresponded to species differences in maximum rates of leaf gas exchange, with S. pulcherrima having the highest K shoot and g s . In most seed plant species, declines in K shoot are associated with the formation of embolism in the xylem (Brodribb et al, 2016b), but declines in hydraulic conductance driven by changes to the pathways of water outside the xylem have also been reported to occur at high Ψ in angiosperm leaves (Scoffoni et al, 2017) and roots (Cuneo et al, 2016(Cuneo et al, , 2020). Here we demonstrate that considerable (up to 80%) reductions in K shoot in two Selaginella species precede embolism formation.…”

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

“…In the present study, the trend toward greater resource investment in existing roots in 110R than in 101-14Mgt could relate to robustness of the respective root systems over time, as well as the likelihood of retaining an overall root structure poised to resume growth and resource acquisition after periods of scarcity [29].…”

Drought-Induced Xylem Embolism Limits the Recovery of Leaf Gas Exchange in Scots Pine

“…Furthermore, storing of NSC in the bark might be important to fuel longitudinal growth and basal area increment of stems in the following year, as has been observed previously for branches (Kagawa et al, 2006), presumably to restore hydraulic conductivity in the long term. By contrast, the observed consumption of root NSC in drought-recovery seedlings might suggest an immediate upregulation of repair and regrowth of root tissues, indicating the preference of resource investments to restore water and nutrient uptake (Hagedorn et al, 2016;Galiano et al, 2017;Cuneo et al, 2020). To transport assimilates to source organs, functional phloem loading and transport are needed.…”