Seed structure dicotyledon

The seeds of dicotyledonous plants have two cotyledons, or seed leaves, which are part of the embryo. The cotyledons usually are the main storage tissue, although in some plants (such as castor bean) the endosperm also has a storage function. During development in the field, seeds gradually accumulate storage oils, proteins and carbohydrates (Table 3.1). In the seed, the cotyledon structure is relatively simple. The remainder of the embryo, the embryonic axis, consists mostly of undifferentiated cells, but provascular tissue can be detected that develops into vascular tissue in the seedling. 

Potato type II (Potll) inhibitors are disulfide-rich peptides of approximately 50 amino acids in size. They were first discovered in leaves, seeds, and other organs of Solanaceae and are a source of much interest as plant defense proteins. Recently, Barta et analyzed expressed sequence tag (EST) and genomic data and discovered 11 genes that code for Potll inhibitors in various monocotyledonous and dicotyledonous plants. Potll inhibitors are expressed as large precursor proteins that contain up to eight sequence repeats of the inhibitor precursor. In one particularly fascinating case from the ornamental tobacco (N. data), the precursor adopts a circular permuted structure.Barta et al. observed that genes outside the Solanaceae family seem... 

Occurrence. Probably 10-20% of all higher plants contain A., and they are particularly numerous and abundant in certain dicotyledonous families. Qosely related families often produce similar A. Usually several structurally related A. are present as hydrophilic salts dissolved in the vacuolar sap. The predominant members of such mixtures are known as primary A., while those present in lower concentrations are secondary A. All parts of the plant may contain A., but they are particularly abundant in seeds, bark and roots. Heterocyclic compounds similar to A. are found in many microorganisms and a few animals (e.g. salamander A.). 

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