Question

Describe the stages in embryo development in a dicot plant.

Answer 1

Dicot plants are plants that have seeds with two cotyledons. Some examples of dicot plants are roses, beans, pea, peanuts, and oak. The embryogenesis of the dicot seed is a multi-stage process where a zygote develops to a proembryo stage, to the quadrant stage, to the octant stage, to a pre-embryo, and finally into a mature embryo.

Complete answer:
Angiosperms or flowering plants are commonly divided into two categories, dicot and monocots. Dicots are plants that produce seeds that have two cotyledons in them, and monocots have one. The embryogenesis of dicots is much more complex and different from that of monocot plants. The embryogenesis begins with the germinated zygote. The zygote divides into a two-cell structure called a proembryo. One end of the cell is known as the basal cell and the other end is known as the terminal cell. The basal cell is divided continuously to form a long slender structure known as a suspensor, whereas the terminal cell divides into a four-cell structure known as the quadrant stage. These cells again divide and form an eight-cell structure, arranged as two four-cell structures and are known as the octant stage. The upper four-cell structure gives rise to the hypocotyl, whereas the lower four-cell structure forms cotyledons and stem tips. Beneath the long suspensor formed by the basal cell is the developing embryo, where the octant cells undergo rapid division, where the outermost cells are called the dermatogen and the inner cell mass is called the periblem and plerome. The dermatogen forms the epidermis whereas the periblem and plerome form the cortex. As the cells keep growing the stem tip, ceases to divide and causes the two cotyledons to grow on each side, giving the characteristic two cotyledon structures. The stem tip is also called the plumule. The cells keep dividing and enlargement of the cotyledons cause it to curve and appear as a horseshoe-like structure

Note: The basal cell along with the four-cell structure which forms the hypocotyl together form the root system of the germinating seed The plumule or stem tip forms the shoot system of the germinating seed.