Water relations during ripening for fruit of well-watered versus water-stressed Opuntia ficus-indica

Water relations and fruit development were studied for up to 100 days after anthesis for potted plants of Opuntia ficus-indica (L.) Mill. (a prickly p ear) that were either well-watered or water-stressed, each plant consisting of a medium-sized cladode bearing two or three fruit. Even though cladodes of water-stressed plants lost up to 50% Of their thickness, their fruit co ntinued to gain water and to develop at ripening such fruit had only 16% le ss water than fruit of watered plants. Maturation indicated by the decrease in fractional peel content and increases in pulp weight and in pulp solubl e sugar content was hastened by water stress,leading to ripening approximat e to 88 days after anthesis for water-stressed plants, which was 10 days ea rlier than for watered plants. Fruit had a lower stomatal frequency than th e cladodes but both exhibited Crassulacean acid metabolism behavior. Transp iration occurred mainly at night, and the daily amount of water transpired per unit fruit surface area decreased with time, especially for fruit of wa ter-stressed plants. This decrease was related to fruit expansion (leading to decreased stomatal frequency) for watered plants and to both fruit expan sion and water stress for water-stressed plants, At 75 days after anthesis, daily diameter changes of fruit mere correlated with transpiration, contra ction occurring at night and expansion during the daytime, and changes were greater for watered plants for which daily transpiration was higher.