The effects of flooding on water relations and growth ofTheobroma cacaovar.catongoseedlings

Abstract

SummarySoil flooding induced stomatal closure and lowered the transpiration rate of Theobroma cacao var. catongo seedlings within 2 h. The early stomatal closure was not associated with leaf dehydration. Subsequent responses to flooding included inhibition of leaf formation and expansion, reduction in dry weight increment and in relative growth rates of leaves, stems and roots (with root growth reduced most), height growth and stem diameter growth. In addition, flooding was followed by leaf epinasty, extensive decay of roots, and formation of hypertrophied lenticels and adventitious roots on submerged stems. The effects of flooding differed quantitatively on dry weight increment and on the relative growth rates of leaves, stems and roots. Flooding the soil in a controlled-environment chamber inhibited seedling growth more than flooding in a greenhouse. The greatly lowered root:shoot ratio of flooded seedlings indicated that drought tolerance of seedlings will be reduced after the flood waters recede because the absorption of water by the small root systems will be too low to meet transpiration requirements. Inhibition of vegetative growth by flooding will probably reduce the yield of T. cacao by prolonging the time to first flowering and by suppressing vegetative growth.