MULBERRY CULTIVATION (CONT...4) - ANATOMY AND EMBRYOLOGY

Anatomy of the Root: Mulberry is a deep rooted perennial plant. Its root system is very well developed though the growth and spread of the root depend upon the texture of the soil.

Internal structure of a root: There is a single layered epidermis which consists of tubular shaped cells, closely arranged without inter‑cellular space, Its outer walls are not cutinized and a few of the epidermal cells enlarge into root hairs.

Structure of a secondary root: The knowledge of anatomy of a root is of primary importance in the vegetative propagation such as selecting a proper plant for preparation of cutting and stock for grafting.

Anatomy of stem: The anatomy of the stem is similar to that of any dicotyledonous stem. The primary stem consists of a single‑layered epidermis with tubular shaped cells closely arranged without inter‑cellular space.

Secondary stem: The secondary stem of mulberry shows the union of the cambial strips of the vascular bundles, a continuous ring of cambium is devel­oped which cuts off secondary xylem towards inside and secondary phloem towards outside.

Anatomy of leaf:

Anatomy of the Petiole: The internal structure of the petiole of mulberry is like the primary tissues of the stem. The epidermis is single layered. Some of the cells are drawn into epidermal hairs in certain species.

Anatomy of leaf blade: The leaves are dorsiventral with reticulate venation. The upper epidermis consists of a single layer of tabular shaped cells closely arranged without intercellular space.

Embryology:

Microsporogenesis: Anther to begin with, is a mass of meristematic cells. A row of three hypodermal cells forms the Archesporial cells. These cells on pericinal division give rise to primary parietal cells and primary sporogenous cells.

Mega sporangium:The mega sporangium or the ovule arises as an out­ growth of thematic cells on placenta. This soon differentiates into funicle and nucellus.

Male Gametophyte: Each pollen grain divides asymmetrically into a large or tube cell and‑a small generative cell. Pollen grains are bicelled at the time of shedding.

Female Gametophyte: The functional megaspore undergoes three successive mitotic divisions forming eight nucleate embryo sac. The embryo sac is pear‑shaped.

Fertilization: After pollination is effected, the pollen grains germinate on the stigma. The rate of growth of pollen tube is generally influenced by environmental con­ditions, especially temperature.

Fruit: The fruit of mulberry is a multiple one, as all the flowers of the inflor­escence give rise to a single fruit.