Carpel development

M-H. Yung, R. Schaffer, J. Putterill. Identification of genes expressed during early Arabidopsis carpel development by mRNA differential display Characterization of ATCEL2, a novel endo-... 

Simon It is just because in the species that I have discussed the carpels are the last organs to develop in the centre of the flower. There are a few exceptions in other plants where the carpels are not so central. We can introduce homeotic mutants that replace carpels with sepals or petals, and the same effects are seen. 

The cotton fibers used in textile commerce are the dried cell walls of formerly living cells. Botanically, cotton fibers are trichomes or seed coat hairs that differentiate from epidermal cells of the developing cottonseed. The cotton flower blooms only for one day and quickly becomes senescent thereafter. On the day of full bloom, or anthesis, the flower petals are pure white in most G. hirsutum varieties. By the day after anthesis, the petals turn bright pink in color and, usually by the second day after anthesis, the petals fall off the developing carpel (boll). The day of anthesis serves as a reference point for all subsequent events in the seed and fiber development. 

In both the flowers develop at least two sets of leaves (either on one or two plants of the same species) called sporophylla or sporophyll leaves, the stamens and carpels. The stamens or stam-inal leaves are also termed microsporophylls. The carpels or carpellate leaves are alscx known as megasporophylls. 

Connation and Adnation.—In the development of the flowers of primitive species of flowering plants, the parts of each whorl are disjoined or separate from each other. In many higher types, however, the parts of the same whorl frequently become partly or completely united laterally. This condition is termed connation, coalescence, cohesion or s)mgenesis. Illustrations of this ihay be seen in Belladonna, Stramonium and Uva Ursi flowers, where the petals have joined laterally to form gamopetalous corollas. When the one or more parts of different whorls are united, as of stamens with petals Rhammus) or stamens with carpels Apocynum) the union is called adnation or adhesion. 

Development of the Anther.—Each stamen originates as a knoblike swelling from the receptacle between the petals and carpels. This swelling represents mainly future soral (anther) tissue. The filament develops later. When such a young sorus or anther is cut... 

Fruits may also be classified into a number of structural types. The individual seed-bearing structures of the flower called carpels constitute the gynoecium. The seed-containing cavity of a carpel is called the ovary, and its wall develops into the pericarp of the fruit. The edible fleshy part of a fruit most commonly develops from the ovary wall, but it may be also derived from the enlarged tip of stem from which floral organs arise, and sometimes leaf-like structures protecting the flowers may also become fleshy, e.g., in pineapple. 

The calyx and corolla show abundant alkaloids in the epidermis. The anthers possess them in the epidermis, the tapetal layers around the developing pollen sacs, and in the bundle sheath of the filament, but not in the vascular elements themselves. Carpels and ovules contain abundant alkaloids in all parts. During the development of the ovule into a seed, its alkaloids diminish and at the resting stage are confined to a single layer of crushed cells on the inside of the testa. The embryo itself and the endosperm are both devoid of alkaloid. The ripe berry has abundant alkaloid in the epidermis, mesocarp, and placenta. 

Leaves show considerable variation in size, shape, arrangement of veins, type of attachment to the stem, and texture. They may be simple or divided into leaflets, i,e, compound (see illustration), Types of leaf include cotyledons (seed leaves) scale leaves, which lack chlorophyll and develop on rhizomes or protect the inner leaves of a bud foliage leaves, which are the main organs for photosynthesis and transpiration and bracts and floral leaves, such as sepals, petals, stamens, and carpels, which are specialized for reproduction. 

Following pollination by wind or insect, the petals are shed and the pistil elongates to form a pod (silique) with two carpels separated by a false septum. A single row of seeds develops within each of the two loculi (Fig. 6). The number of seeds per pod varies with the species, form, and environment, but normally a pod contains between 15 and 40 seeds. At maturity the... 

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