UL REDOX POTENTIAL AND LEAF STOMATAL CONDUCTANCE OF TWO S ROOTSTOCKS SUBJECTED TO FLOODING AND ROOT WEEVIL FEEDING

摘要

In 2002, a greenhouse study was conducted to determine the effects of different flooding durations on soil redox potential, and to compare the interaction of flooding and larval mot weevil (Diaprepes abbreviates L.) feeding on citrus seeding leaf stomatal conductance and root damage. The experimental design was completely randomized with two rootstocks (Swingle citrumelo (SWI) and Smooth Flat Seville (SFS)}, four flooding durations (0,10,20, and 30 days), and larval feeding for 42 days. Plants were flooded, drained for a week, and then five neonate larvae per seedling were introduced onto the soils. Flooding significantly reduced soil redox potential (P< 0.001); and flooding, rootstock variety, and their interaction significantly affected leaf stomatal conductance (P < Q.0G1). After flooding, soil redox potential dropped from ..;200mV to below -100 mV within 1-3 days, and plant leaf stomatal' conductance declined from 260 mmol nr2s-1 to 60 mmol nr2s-1 after 30 days for SWI. Swingle appeared to be more tolerant of water stress by flooding than SFS. Survival of Diaprepes larvae was higher in flooded treatments than non-flooded treatments (P < 0.05). Flood damaged seedlings were more susceptible to root injury by larval feeding than non-flooded seedlings. Treatments flooded for 10 days had higher stomatal conductance and lower root injury from larval feeding than those flooded for 30 days. We conclude that negative soU redox potential and a decrease of leaf stomatal conductance might be useful as early indicators of plant water stress iv&vi Hooding and root damage from weevil larval feeding.