ABSTRACT
Papaya is a tropical plant and very sensitive to frost, limited to the region between 32° north and 32° south of the Equator. It is grown up to an elevation of 1200 m above the mean sea level. It needs plentiful rainfall or irrigation, but must have good drainage. Flooding for 48 h is fatal to it. Brief exposure to 32°F is damaging; prolonged cold without overhead sprinkling can kill the plant (DAIS 2009). Although a mature papaya tree can withstand a temperature of −2°C, production is only recommended in areas where the average daily minimum temperature during mid-winter never drops below 5°C. Ideally, night temperatures should not drop below 12°C. The optimum temperature range for papayas is between 25°C and 30°C. Temperatures higher than 36°C and lower than 16°C for extended periods can adversely affect the growth of the trees. It grows well in regions where summer temperature ranges from 35°C to 38°C. It requires 23°C average daily temperature and 6 months for flowering to fruit maturity. Although papayas are considered sun-loving plants, morphological plasticity in the shade is high and involves changes in many characteristics such as leaf mass per area, chlorophyll a and b ratio, stomata density, internode length and degree of blade lobbing (Buisson and Lee 1993). This plasticity is evidenced by the morphology adopted by papayas growing in multi-storied agro-ecosystems and in high-density orchards as well (Iyer and Kurian 2006). The lower the temperature, the longer the time it will take for fruit maturity with round fruit shape. After the winter, trees are in a recovering stage and produce few flowers. In subtropical conditions, however, growth and flower production cease when the night temperature drops below 12°C.
