EFFECTS OF FLOODING AND DROUGHT ON ETHYLENE METABOLISM, TITRATABLE ACIDITY AND FRUITING OF PINEAPPLE

Pineapple can be induced to flower with ethylene but no data was found on the effects of stress due to flooding or drought (which increase ethylene production in some plants) on pineapple flowering. The effects of intermittent (three times daily) and continuous flooding and drought on tissue ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity, leaf relative water content (RWC), leaf titratable acidity (TA), and fruiting of pineapple [Ananas comosus (L.) Merr.] were studied using pot-grown plants. With intermittent flooding, ethylene production and ACC oxidase activity of leaf basal, white tissue increased while that for stem tissue decreased. With continuous flooding, ethylene production by leaf and stem tissue was not different from the control, but ACC oxidase activity decreased. Drought stressed plants produced significantly less ethylene and had lower ACC oxidase activity in leaf and stem tissues than control plants had. RWC and TA measured at dawn decreased significantly as the duration of flooding or drought increased. On relief of the stress, leaf TA and RWC increased more rapidly for drought-stressed than for flooded plants. No treatment induced pineapple plants to flower. Plants induced to flower with 2-chloroethylphosphonic acid (ethephon) after continuous flooding or drought stress had significantly smaller fruits than control plants. Under the conditions of these studies, flooding and drought stress had no effect on flower induction, but significantly reduced pineapple fruit mass.