Physiological responses of apricot plants grafted on two different rootstocks to flooding conditions

The effects of soil flooding on plant water relations and vegetative growth was studied in potted two-year-old apricot plants (Prunus armeniaca L., cv. Búlida) grafted on two different rootstocks: Pollizo prune (P. insititia L.) (P) and Real Fino apricot (RF). Plants were submitted to three outdoor treatments: T0, not flooded (control), and two flooded treatments for 3 (T1) and 6 (T2) days. Apricot water relations were seen to be adversely affected from the first day of the flooding onwards. These effects were more pronounced in Búlida/RF than in Búlida/P plants. The T1 plants developed an early stomatal regulation [decrease in leaf conductance (gl)], which prevented leaf tissue dehydration, together with a decrease in net photosynthesis (Pn) and an increase in resistance to water flow (R(p+s)). This early gl and Pn response suggests that porometric and/or photosynthetic changes are reliable bio-indicators of the altered behaviour caused by flooding in apricot plants. The lowest gl and Pn, and highest R(p+s) values occurred with more prolonged flooding (6 days), when a decrease in leaf water potential (ψl) and leaf turgor was noted, together with epinasty, which in Búlida/RF plants led to a decrease in ψl to -6.0 MPa, and the death of all plants. These results indicate Búlida apricot plants grafted onto Pollizo prune rootstock is a more appropriate combination than Búlida/Real Fino to resist occasional soil flooding situations.