BSC 314 Lecture Notes - Lecture 18: Germination, Flowering Plant, Stamen
26 Jun 2018
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Features of Flowers
Flowers arise from apical meristems similar to vegetative shoots but, unlike them, have
determinate growth. The floral primordia develop into four different kinds of specialized
leaves that are borne in whorls at the tip of the stem (see Figure ). The two outer whorls
are sterile, the inner two fertile. The first formed outer whorl—the calyx— is the most
leaflike and its individual parts, the sepals, often are green. The petals of the next
whorl, the corolla, frequently are brightly colored and in a majority of flowers retain
some semblance to leaves. (Together the calyx and the corolla are called the perianth.)
The next two whorls, the androeciumand the gynoecium, are composed of highly
modified reproductive structures that have lost their leaf like appearance. The ‐
androecium is composed of stamens and the gynoecium of carpels. ( Pistil is
sometimes used as the term for a single carpel or a group of fused carpels.) The
stamens are microsporophylls and have a stalk, the filament, at the top of which
the pollenbearing‐ anthers are located. A carpel is a megasporophyll and has as its
base an enlarged ovary from which the style bearing a stigma arises. The whorls are
attached to the receptacle area at the end of the flower stalk or pedicel. Some flowers
arise singly, but more are produced and arranged in groups called inflorescences. The
stalk of an inflorescence is the peduncle and the extension of the axis in the
inflorescence is the rachis, to which the pedicels of the individual flowers are attached.
Seed and Fruits
Seeds develop from ovules in the ovary, and at maturity consist of an embryo and a
reserve food supply surrounded by a protective covering, the seed coat. The diversity
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Document Summary
Flowers arise from apical meristems similar to vegetative shoots but, unlike them, have determinate growth. The floral primordia develop into four different kinds of specialized leaves that are borne in whorls at the tip of the stem (see figure ). The two outer whorls are sterile, the inner two fertile. The first formed outer whorl the calyx is the most leaflike and its individual parts, the sepals, often are green. The petals of the next whorl, the corolla, frequently are brightly colored and in a majority of flowers retain some semblance to leaves. (together the calyx and the corolla are called the perianth. ) The next two whorls, the androeciumand the gynoecium, are composed of highly modified reproductive structures that have lost their leaf like appearance. The androecium is composed of stamens and the gynoecium of carpels. ( pistil is sometimes used as the term for a single carpel or a group of fused carpels. )
