FLOODING AFFECTS FRUITLET ABSCISSION IN SATSUMA MANDARIN
We tested the effect of soil hypoxia from flooding on fruit drop in a mature orchard of Satsuma mandarin (Citrus unshiu Marcow) trees on Pomeroy (Poncirus trifoliate (L.) Raf.) rootstock. Trees were flooded for 30 days with 10 cm water above the soil surface using a 60 cm high aluminum barrier which was buried to depth a 45 cm around the trees. Flooding began at flower anthesis and lasted until early fruit set. Flooding reduced the soil oxygen levels from 5 to 2 µg O2 cm-2 min-1. Relative fruit drop rate was higher in flooded trees than in non-flooded trees and the spring flush shoot numbers was reduced by flooding but not shoot length. Shoot water potential was reduced but leaf chlorophyll was not affected in leaves. Flooding immediately reduced net CO2 assimilation rate (ACO2), stomatal conductance and reduced quantum yield efficiency of the PSII after 3 weeks. There were only small changes in internal CO2 concentration in leaves and no changes in maximum quantum efficiency (Fv/Fm) or basal chlorophyll florescence (Fo). This suggested that non-stomatal factors were more important than stomatal factors in limiting ACO2. Root function was reduced and an accumulation leaf starch was related to early fruit drop. Soil hypoxia from anthesis to early fruit set induced fruitlet abscission in Satsuma mandarin and was linked to tree water relations.
Carmen Goñi, , Alvaro Otero, and James P. Syvertsen, (2015). FLOODING AFFECTS FRUITLET ABSCISSION IN SATSUMA MANDARIN . Acta Hortic. 1065, 1407-1416
hypoxia, fruit drop, leaf photosynthesis, leaf fluorescence