Effect of temperature on inflorescence and floral development in four mango (Mangifera indica L.) cultivars

Abstract

To study the effect of low temperature on inflorescence and floral development of mango (Mangifera indica L.), `Nam Dok Mai', `Kensington', `Irwin' and `Sensation' trees were exposed to natural winter temperatures to induce flowering, and then transferred to controlled-environment glasshouse rooms where day/night temperature regimes of 15/5°, 20/10°, 25/15° and 30/20°C were maintained for 20 weeks. Day/night temperatures of 15/5°C severely inhibited the emergence and elongation of inflorescences of all cultivars with inflorescence development only occurring on trees that were maintained at the warmer temperatures (20/10°, 25/15° and 30/20°C). The time taken for inflorescences to reach maximum length was 15–20 days on trees held at 25/15° or 30/20°C but extended to 54 days on trees kept at 20/10°C. Warmer temperatures generally increased the inflorescence size of all cultivars. At 20/10°C, pollen viability of `Sensation' was significantly lower than the other cultivars, but there was no significant difference between cultivars held at 25/15° and 30/20°C. Low temperatures caused morphological changes in styles, stigmas, ovaries and anther size in all cultivars, and changes were especially pronounced in `Kensington'. Style length and stigma width of all cultivars were reduced when trees were held at 20/10°C compared to trees held at either 25/15° or 30/20°C. Trees of `Kensington' grown at 20/10°C mainly produced flowers that had short styles (0.62 mm) and small stigmas (0.09 mm) while `Nam Dok Mai' and `Irwin' trees produced some flowers with deformed or fused ovaries. Scanning electron microscopic studies indicated that normal `Kensington' flowers had non-symmetrical stigmas that were covered with undeveloped papillae cells. The short-styled `Kensington' flowers (produced at 20/10°C) had a much smaller receptive stigmatic area compared to normal flowers produced at 30/20°C. Low temperature-induced (20/10°C) changes in ovary size in `Nam Dok Mai' and style length in `Kensington' flowers may contribute to low fruit set in these two cultivars when grown in subtropical climates.