Growth, Leaf Chlorophyll Concentration, and Morphological Adaptation of Selected Wax Apple Cultivars in Response to Flooding

Abstract

Growth, leaf chlorophyll concentration and morphological adaptation of young wax apple (Syzygium samarangense (Blume) Merrill & Perry) cvs. Plastic (PT), Thunklao (TK), Phetnamphueng (PP) and Thapthimchan (TC) and Malay apple (Syzygium malaccense) (MA) plants under flooding
conditions were investigated. Potted wax apple and Malay apple plants were flooded to 5 cm above the soil surface for 70 days continuously. MA, TK, PP and TC plants survived under this flooding duration while PT plants had gradually died after flooding for 30 days. Vertical splitting of the outer bark was observed immediately above and below the flood level in all cultivars after flooding for 12 – 21 days followed by a development of adventitious roots at stem base below the flood level in most cultivars except for MA plants. Flooded PT plants formed adventitious roots faster than other cultivars while flooded TC plants had greatest mass of adventitious roots. Flooding significantly decreased shoot length, leaf number, leaf area, leaf chlorophyll concentration and dry weight of leaves and roots but increased shoot to root ratio. Severe growth restriction was observed in flooded MA and PT plants. Based on the ability to maintain growth under flooding conditions, PP was the most flood tolerance cultivar with profuse adventitious roots followed by TK and TC, respectively, while PT was the least flood tolerance in this study. MA plants restricted their growth and maintained leaf chlorophyll level to survive flooding without adventitious root formation. The results suggested that these selected wax apple cultivars and Malay apple tolerated to flooding differently and flooding tolerance was not generally associated with the ability to form adventitious roots under flooding conditions.