![]() ![]() As in the case of bananas, triploid watermelons cannot produce functional seed, but they still develop good fruit through parthenocarpy. One way to make seedless watermelons is to produce triploid seed. Seedless watermelons are particularly interesting because they must be propagated by seed, and yet growers can still exploit parthenocarpy. Growers also propagate bananas by tissue culture. But there are side shoots or suckers at the base of the main stalk, which can be removed and replanted to continue the cultivar. After the stalk has flowered and borne fruit, it dies. Bananas, too, are parthenocarpic and produce fruit in the absence of successful fertilization. Triploids seldom produce eggs or sperm that have a balanced set of chromosomes and so successful seed set is very rare. ![]() Instead of having one set of chromosomes from each parent, it has two sets from one parent and one set from the other parent. In other words, it has three sets of chromosomes. For example, the common banana is triploid. Instead nurserymen frequently propagate fruit trees asexually, usually by grafting.Īnother frequent reason for lack of successful fertilization is chromosomal imbalance. In fact, propagation by seed would be disadvantageous because the progeny would differ from the parent. Such trees do not require seed for propagation. These plants have a high frequency of parthenocarpy, however, so they still produce fruit. Because these cultivars are self-incompatible, they fail to set seed when they are planted in orchards of identical plants (clones). This property is exploited by citrus farmers who grow seedless fruits, such as navel oranges and clementines. In many plants, self-incompatibility genes limit successful fertilization to cross-pollination between genetically different male and female parents. The most frequent reasons for lack of seed development are pollination failure, or nonfunctional eggs or sperm. SEEDLESS FRUIT such as navel oranges are propagated asexually, usually by grafting. ![]()
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