Growth and Development of Horticultural Crops (1+1)

Introduction

• The embryo, or embryonic plant, is the beginning of a new generation. A reserve of stored food, either as cotyledons attached to the embryonic axis or as endosperm tissue, functions as an initial source of nourishment for the embryonic plant until it attains an independent autotrophic existence. The seed coat serves to protect the embryo against adverse environmental conditions and, in some cases, is adapted as a means of seed dispersal. The early developmental stages of the embryo sac are nourished by the cells of the surrounding ovulary tissue. These cells are originally rich in starch, lipids, and proteins, which are subsequently hydrolyzed to form soluble sugars, amino acids, organic acids, and other metabolically active materials. The ovule is also connected to the main transport system of the plant by a vascular strand through which water, ions, and the other solutes are supplied to the developing seed.
  
• The diploid nucleus of the zygote receives one chromosome complement from the female parent (Egg) and one from the male parent (sperm). Thus the zygote contains all the genetic information necessary for development of a mature plant. It is obvious, however, that the cells in a seedling or mature plant are not alike and that these differences arise very early in the life of the plant. The first division of the zygote forms two cells, which are generally different in size. Further divisions of these cells lead to embryonic development and the differentiation of tissues and organ systems characteristic of the plant.