Drought and water excess

Few quantitative studies of the effects of drought on fruit development were found. E. Malézieux (1992, unpublished results) found that the expected fruitlet number was reduced by drought, and Chapman et al. (1983) reported that prolonged drought of pineapple grown in pots reduced fruit weight to the extent that it was commercially unacceptable. If stress occurs during fruit development, the peduncle can become shrivelled and the fruit may lodge or break off (Swete Kelly and Bartholomew, 1993).

In Côte d'Ivoire, the fruit weight of plants grown in the field was related to the percent

Irradiance (MJ m-2 day-1)

Fig. 8.6. Effect of mean irradiance from planting to harvest on average fruit weight of 'Smooth Cayenne' pineapple. Data are means of 60 fruits harvested from 72 monthly plantings in Côte d'Ivoire during a 6-year period. All plants were forced 8 months after planting. (Redrawn from Bartholomew and Malézieux, 1994.)

Irradiance (MJ m-2 day-1)

Fig. 8.6. Effect of mean irradiance from planting to harvest on average fruit weight of 'Smooth Cayenne' pineapple. Data are means of 60 fruits harvested from 72 monthly plantings in Côte d'Ivoire during a 6-year period. All plants were forced 8 months after planting. (Redrawn from Bartholomew and Malézieux, 1994.)

age of water requirement provided by irrigation between flowering and harvest (Combres, 1980). A 17% decrease in fruit weight occurred when only 20% of the plant water requirement was provided during this period. In Côte d'Ivoire, a dry period that occurs during the month after forcing can reduce the number of fruitlets and a drought that occurs at the end of fruit development reduces fruitlet weight (E. Malézieux, 1992, unpublished results). Average fruit-weight differences at harvest between irrigated and unirrigated plots can reach 750 g when the dry season is severe (Combres, 1983). Yield increases of 30% due to biweekly irrigation during fruit development were obtained in Taiwan (Huang and Lee, 1969). In Côte d'Ivoire, yields were 12-15 Mt ha-1 greater with irrigation in a normal year (Combres, 1979; Malézieux and Sébillotte, 1990b) and 25-30 Mt ha-1 greater when drought was severe (Combres, 1979). While Huang and Lee (1969) reported that irrigation had no effect on fruit quality, Linford and Magistad (1933) found translucence was greater and acidity was decreased in fruit from irrigated plots. Beyond the effects on vegetative growth and fruit development, drought can also reduce sucker production (Medcalf, 1950), and reductions of up to 50% were observed at the end of the dry season (Combres, 1979).

While few quantitative data on the effects of water excess on growth under field conditions were found, yields were reduced by 15% (about 10 Mt of exportable fruits) in Côte d'Ivoire when plants were irrigated at 140% of the water requirement for the period between flowering and harvest (Combres, 1983). Until recently, when good fungicides became available to control Phytophthora spp., loss of plants to root and plant rots was a greater concern than reduced growth due to waterlogging (Rohrbach and Apt, 1986; Rohrbach and Johnson, Chapter 9, this volume).

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