Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 218

When a flower has all the four major parts, it is said to be a complete flower (e.g. soybean, tomato, cotton, tobacco). However, if a flower lacks certain parts (often petals or sepals) as is the case in many grasses (e.g. rice, corn, wheat), it is said to be an incomplete flower. Some flowers either have only stamens or a pistil, but not both. When both stamens and a pistil occur in the same flower, the flower is said to be a perfect flower (bisexual), as in wheat, tomato, and soybean. Some flowers are unisexual (either stamens or pistil may be absent) and are called imperfect flowers. If imperfect flowers have stamens, they are called staminate flowers. When only a pistil occurs, the flower is a pistillate flower. A plant such as corn bears both staminate (tassel) and pistillate (silk) flowers on the same plant and is said to be a monoecious plant. However, in species such as asparagus, and papaya, plants may either be pistilliate (female plant) or staminate (male plant) and are said to be dioecious plants. Flowers may either be solitary (occur singly or alone) or may be grouped together to form an inflorescence. An inflorescence has a primary stalk (peduncle) and numerous secondary smaller stalks (pedicels). The most common inflorescence types in crop plants are the cyme and raceme. A branched raceme is called a panicle (e.g. oats) while a raceme with sessile (short pedicels) is called a spike (e.g. wheat). From the foregoing, it is clear that a plant breeder should know the specific characteristics of the flower in order to select the appropriate techniques for crossing.