BOTANY WITH BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

VIII. BASICS OF PLANT MORPHOLOGY AND ANATOMY

Features of angiosperm reproduction

Adaptations in bisexual flowers that prevent self-pollination

About 75% of plant species have bisexual flowers, yet self-pollination does not occur in them; through evolution, they have developed special morphological and physiological adaptations to prevent it. In particular, these include unisexual (male and female) flowers, dioecious plants, dichogamy, heterostyly, and self-incompatibility.

Unisexuality of flowers, and especially plant dioecy, is a reliable adaptation against self-pollination. In monoecious plants, unisexual flowers exclude autogamy, but do not prevent geitonogamy, i.e., neighboring Fertilization.

The asynchronous maturation of stamens and pistils (dichogamy) is a functional unisexuality caused by the non-simultaneous

maturation of stamens and pistils within the same flower. It manifests as protandry, where anthers mature earlier than pistil stigmas (raspberry, strawberry), and protogyny, where stigmas mature before anthers (apple, pear, plum). The simultaneous maturation of pollen and stigmas in a bisexual flower is called homogamy, which enables self-pollination.

Heterostyly is the unequal length of styles and stamen filaments within an individual flower (lungwort, buckwheat, primrose, forget-me-not). In this case, pollen from long stamens cannot germinate on short styles, nor can pollen from short stamens germinate on long styles, meaning fertilization within the same flower cannot occur. For fertilization to take place, pollen from long stamens must reach long styles, or pollen from short stamens must reach short styles, originating from other flowers.

Self-sterility (auto-sterility, self-incompatibility) is the inability of pollen to germinate on the stigma of a bisexual flower of the same plant (rye, carrot, beet).

In apples, pears, sweet cherries, sour cherries, and plums, self-pollination does not occur not only with pollen from its own flower or another flower on the same tree, but even with pollen from a different tree of the same cultivar. This phenomenon is termed self-sterility, and it is particularly pronounced in apples and pears.

Scientists have identified three groups of apple cultivars regarding their self-pollination capacity: self-fertile cultivars capable of self-pollination, such as 'White Astrarakhan', 'Suislepp', 'Malynivka' (V.V. Pashkevych, 1931), 'Osinnie Krymske' (A.N. UsoV and A.A. Lyapikhova, 1984); partially self-fertile cultivars such as 'Renet Symyrenko', 'Sary Sinap', 'Renet Champagne', 'Kandil Sinap' (I.N. Ryabov, 1930, 1934), 'Salgirske', 'Golden Delicious', 'Krymske', 'Tavriya', 'Suvenir', 'Salyut' (A.N. Usov and A.A. Lyapikhova, 1984); and cultivars with low self-fertility, such as 'Obilne', 'Sevastopolske', 'Evryka', 'Avrora Krymska' (A.N. Usov and A.A. Lyapikhova, 1984).

When establishing commercial orchards with cultivars that have low or partial self-fertility, to prevent its effects, one row of a pollinizer cultivar is planted for every five to six rows of the main cultivar.