Root respiratory components of Prunus spp. rootstocks under low oxygen: Regulation of growth, maintenance, and ion uptake respiration

Hypoxia in the root zone activates several mechanisms to cope with the energetic imbalance that triggers hypoxia. Prunus is a hypoxia-sensitive species, and there is not information about the relationship between components of the root respiration and the hypoxia tolerance. We investigated whether adjusting root respiratory components plays a role in the hypoxia tolerance in Prunus rootstocks genotypes. Three Prunus rootstocks genotypes, 'Mariana 2624' (tolerant), 'CAB6P' (moderately sensitive) and 'Mazzard F12/1' (sensitive), were exposed to normoxia and hypoxia in a hydroponic system for 30 days. During the first 10 days of the experiment, the hypoxia-tolerant genotype under hypoxia exhibited a higher root relative growth rate, maintained net nitrogen uptake rate, and had lower protein turnover and electrolyte leakage, as well as increased root porosity (aerenchyma formation from 0.3 to 6.0 cm from the root tip at 30 days of experiment) compared to hypoxia-sensitive genotypes. 'Mariana 2624' roots exhibited tolerance to hypoxia by reducing maintenance respiration by 50% compared to normoxia, while growth respiration increased. Control of root respiratory components, early response of ion uptake favors root relative growth rate, and change of the root anatomy are associated with the ability to tolerate hypoxia by reducing maintenance costs.