Physiological Effects of Environmental Factors and Growth Regulators on Floral Initiation and Development of Pineapple [Anans comosus (L.) Merr.]

Abstract

To improve the understanding of environmental control of pineapple flowering and the ability to manipulate this process, the effects of temperature, water stress, and growth regulators on natural flowering or ethephon-induced flowering of ’Smooth Cayenne’ pineapple were studied. A night temperature of 30 °C reduced pineapple CO2 dark fixation relative to that 20 °C. Plants grown at a 30 °C night temperature tended to produce less ethylene and had lower 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCOase) activity. Plants transferred from a 30/20 to a 30/30 °C day/night temperature regime immediately after treatment with ethephon were not induced to flower. Plants grown in the constant 30/30 °C regime were forced but produced fruits with significantly fewer fruitlets per fruit than did plants grown in a 30/20 °C environment. Both water excess and water deficit stress significantly reduced dark CO2 fixation. Water excess stress imposed by flooding pots three times per day promoted ethylene production and ACCOase activity of leaf basal-white (basal) tissue, but has no effect on ethylene production and ACCOase activity of stem apical (stem) tissue. Water deficit stress significantly decreased ethylene production by leaf basal tissue and ACCOase activity of leaf basal and stem tissues, but had no effect on ethylene production by stem tissue. Neither water excess nor water deficit stimulated natural flowering. However, both water excess and water deficit imposed after forcing with ethephon reduced fruitlet number and fruit size relative to the control. Fruitone, paclobutrazol and uniconazole delayed or inhibited flowering, while aminooxyacetic acid, aminoethoxyvinylglycine, daminozide, and silver thiosulfate had no effect. Uniconazole and paclobutrazol inhibited ethylene production and ACCOase activity of leaf basal tissue, which may account for their effect on flowering. Fruitone stimulated ethylene production and increased ACCOase activity and malonyl-ACC (MACC) content in stem tissue, but the mechanism by which it delayed or inhibited flowering is not known. It is concluded that a 30 °C night temperature decreased CO2 fixation and reduced the flower induction response and fruitlet numbers. Water stress clearly is not a main factor in controlling flower induction. Fruitone, uniconazole and paclobutrazol delay or inhibit flowering of pineapple.