Cell<Tissues---Animal Tissues and Plant Tissues~

Plant Tissues—-Meristematic and Permanent~

Meristematic Tissues~ The growth tissue. Cells divide continuously. Thin cell walls(made of cellulose). Nucleus(large). Dense cytoplasm. No vacuoles. No intercellular space.

  1. Apical Meristem- For height increase. At tips of root and shoots.

  2. Lateral Meristem-For girth(thickness). At around the stems and roots beneath them in vascular form. The cambium.

  3. Intercalary Meristem-For regrowth. At internodes and bases of leaves.

Mature Meristematic cells which have been dividing and lose their ability to divide further, take up a permanent role or function, and turn into Permanent Tissues, this process is called differentiation.

Permanent Tissues~ Inability to divide.

  • Protective tissue- Epidermis-

Outermost layer of plants. Tightly packed cells. Rectangular cells. ‘Skin’. Single layer, flat cells. Covered with waxy layer-Cuticle- thick in dry habitations. For water loss. Made of cutin(secreted by epidermal cells). No intercellular space.

  1. In roots: arised projections from epidermal cells are called root hairs(for absorbing water, minerals from soil).

How do root hairs arise?

The parts of plant exposed to air-have cutinised hair(of cuticle. waxy tiny outgrowths. On the epidermis)- trichomes-reduce the rate of transpiration(reduce water loss)

But in roots, tips of roots don’t have cutinised hairs-layer is Epiblema(give rise to root hairs)-only on tips.

In older parts of roots, epiblema is replaced by a protective tissue(it wears off) -Exodermis(underneath the epiblema).

  1. In leaves: epidermis has pores-Stomata-transfer of gases and help in tranpiration.