Search Results

You are looking at 11 - 13 of 13 items for

  • Author or Editor: Avinoam Nerd x
Clear All Modify Search

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 pear) 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 continued to gain water and to develop; at ripening such fruit had only 16% less water than fruit of watered plants. Maturation indicated by the decrease in fractional peel content and increases in pulp weight and in pulp soluble sugar content was hastened by water stress, leading to ripening ≈88 days after anthesis for water-stressed plants, which was 10 days earlier than for watered plants. Fruit had a lower stomatal frequency than the cladodes but both exhibited Crassulacean acid metabolism behavior. Transpiration occurred mainly at night, and the daily amount of water transpired per unit fruit surface area decreased with time, especially for fruit of water-stressed plants. This decrease was related to fruit expansion (leading to decreased stomatal frequency) for watered plants and to both fruit expansion and water stress for water-stressed plants. At 75 days after anthesis, daily diameter changes of fruit were correlated with transpiration, contraction occurring at night and expansion during the daytime, and changes were greater for watered plants for which daily transpiration was higher.

Free access

Hylocereus is a night-flowering cactus, whose hermaphrodite flowers reach a diameter of 22 cm. It was found in early studies that both self-fertility and self-sterility occur among the 14 species introduced to Israel. Flowers of all species behaved similarly concerning the phenology of flower opening and closing. Flowers opened about 1 hr. before sunset and were completely closed at approximately 6 hrs. after sunrise. Handcross-pollination led to 100% fruit set until 24 hrs. after flower opening, after which time both stigma receptivity and pollen germinability declined. Crossings between species bearing red fruits led to a higher fruit weight (424±134 g) in comparison to crossings between red-fruited species and species with yellow spiny fruits (146±64 g). Pollen germination in vitro for red-fruited species ranged from 23 to 59% but was only 0.7% for yellow-fruited species. To test the effectiveness of the honey bee as a pollinator a beehive was placed inside a nethouse. The flowers were visited by bees mainly in the morning; the bees foraged on pollen and eventually touched the stigmata of the flowers. Both the regularity of bee visits and the percentage of fruit set after bee visitation was very low (19%). This might be due to the fact that flowers were not constantly available; therefore the bees did not accept them as a constant and reliable pollen source.

Free access

Twenty-four genotypes of marula (Sclerocarya birrea subsp. caffra) were characterized using randomly amplified polymorphic DNA (RAPD) analysis. A distinct band pattern was obtained for each of the trees, using as few as four arbitrary 10-mer primers. Trees propagated vegetatively by grafting showed identical fingerprints. These results suggest that RAPD markers provide a useful system for documenting the identity of marula genotypes.

Free access