Tesis Doctorado
Physiological and Anatomical Responses of Grapevine Roots to Drought Stress and Recovery after Re-watering
Physiólogical and anatomical responses of grapevine roots to drought stress and recovery after re-watering
Autor
Cuneo-Arratia, Italo
Institución
Resumen
In this dissertation, root systems of different grapevine rootstocks have been examined in their response to drought and re-watering and in their ability to take up water through woody roots. Fine roots are commonly thought to be a weak link in the soil-plant-atmosphere continuum, capable of breaking the water transport pathway in conditions of drought stress. However, the exact site and the sequence of this dysfunction is not known. In the first chapter, we utilized x-ray microtomography (microCT) to explore in vivo changes in structure and embolism formation, and we complemented these studies with hydraulic experiments to test how the hydraulic properties of the radial pathway were affected by drought. We found that lacunae formation in fine root cortical cells, and not embolism formation, is the initial and primary driver of reduced fine root hydraulic conductivity (Lpr). After re-watering, we found no recovery of Lpr, even though the stem water potentials (stem) and stomatal conductance did recover. In the third chapter, we hypothesized that when root systems have limited amounts of fine roots, some water uptake must happen through suberized woody roots. Using microCT and hydraulic measurements, we found that when water is delivered to suberized woody roots, hydration of the bark occurs first and is then followed by water absorption in the xylem and embolism removal (~20% of vessels refilling completely within 15 h). Hydraulic experiments showed that while Lpr of suberized woody roots is 0.7% of the Lpr found in fine roots, woody roots are still conductive and water uptake can occur when fine roots are absent. For the fourth chapter, two commonly used grapevine rootstocks were tested for their physiological performance under mild to severe drought stress and subsequent recovery. We used neutron radiography (NR), microCT, fluorescent microcopy and hydraulic measurements to get a detailed picture of the physiological mechanisms that might contribute to drought tolerance/susceptibility in grapevine rootstocks. We found that the drought resistant rootstock examined (i.e. 110R) showed a faster decline in Lpr during mild drought stress and a rapid recovery of root elongation and Lpr after re-watering. The observed changes in hydraulic properties coincide with lacunae formation during mild drought stress and with the recovery in root elongation after re-watering. The integration of response to drought and hydraulic recovery after re-watering is important for understanding drought tolerance in grapevine rootstocks. PFCHA-Becas PFCHA-Becas