UNIT 4: PLANT TISSUE

MERISTEMATIC TISSUE A flowering plant has the ability to grow its entire life because it possesses meristematic (embryonic) tissue. The apical meristem are located at or near the tips of stems and roots, where they increase the length of their structures by means of mitosis. This increase in length is called primary growth. Monocots also have an intercalary meristem, this allows them to regrow lost parts. (It is found between mature tissues). EXAMPLE: GRASS CUT - GROW

Organization of a plant body MERISTEMATIC TISSUE AT TIP OF STEM MERISTEMATIC TISSUE AT TIP OF ROOTS

SPECIALIZED PRIMARY TISSUES: APICAL MERISTEM Produces three types of meristems, and these develop into the three types of specialized primary tissues in the body of the plant: SPECIALIZED PRIMARY TISSUES:  Protoderm gives rise to the epidermis Ground meristem produced ground tissue Procambium produces vascular tissue

FUNCTIONS OF SPECIALIZED TISSUES Epidermal tissue: forms the outer protective covering of a plant. Ground tissue fills the interior of a plant. Vascular tissue transports water and nutrients in a plant and provides support.

EPIDERMAL TISSUE

EPIDERMAL TISSUE Single layer of closely packed, flat, brick shaped cells, with a large vacuole. The aerial parts of the plant are covered with a cuticle. Functions: - Cuticle minimizes water loss (because it has cutin) - Protects the plant against bacteria. Longitudinal section Cross section

Leaf contain upper and lower epidermal cells

SPECIALIZE EPIDERMAL CELLS TRICHOMES ROOT HAIR TRICHOMES STOMA OF LEAF CORK OF OLDER STEMS ROOT HAIRS STOMATA CORK CELLS

ROOT HAIRS They are specialized epidermal cells of roots. Unicellular outgrowth of the epidermal cell. Functions: Increase the surface area of the root for absorption of water and minerals. Anchor the plant.

TRICHOMES Specialized epidermal cell of stems and leaves. Multicellular outgrowths of the epidermis of stems and leaves. Functions: Protect the plant from sun Conserve moisture. Protect plant from herbivores, produce toxic substance. CUTICLE MULTICELLULAR

STOMATA Specialized epidermal cells called guard cells, which are bean shaped, enclose an opening called the stoma or pore. The guard cells contain a nucleus and chloroplasts. It has a thick inner membrane and a thin outer membrane. Woody plants have lenticels. FUNCTIONS: Transpiration Gaseous exchange take place through the stomata. Thick inner membrane Thin outer membrane

CLOSED- NIGHT OPEN - DAY

PARENCHYMA COLLENCHYMA SCLERENCHYMA GROUND TISSUE PARENCHYMA COLLENCHYMA SCLERENCHYMA

GROUND TISSUES

PARENCHYMA TISSUE FUNCTIONS: Occur in roots, stems and leaves. If they have chloroplasts – photosynthesis. If they have leucoplasts – they store products of photosynthesis. They can divide to form more specialized cells Occur in roots, stems and leaves. Spherical, loosely packed, big, thin-walled cells with large vacuoles. Intercellular airspaces between cells.

INTERCELLULAR AIR SPACES PARENCHYMA CELLS

COLLENCHYMA TISSUE FUNCTIONS: Mechanical strengthening and support to plant organs It is composed of unevenly thickened primary walls with additional cellulose and pectin deposits especially in the corners. Found just beneath the epidermis of young stems. The cells are slightly elongated, tightly packed and overlap each other.

SCLERENCHYMA TISSUE Cell walls have been thickened by impregnation with lignin. The cell wall is evenly thickened and forms a waterproof barrier impermeable to water. In the cell walls are pit canals that serve as channels between cells and to the outside world. The lumen is small. Two types of Sclerenchyma: Stone cells and fibers FUNCTIONS: Strengthening, support and protection. Found in shell of nuts and hard parts of fruits Fibers give rigidity and flexibility to the plant.

Vascular tissue XYLEM PHLOEM

XYLEM Contains 2 types of conducting cells: tracheids and vessel elements (VE). Both cells are hollow and non-living but the VE is larger and has perforated plates in their end walls and are arranged to form a continuous vessel. Tracheids have tapered ends with pits. It also has other tissue: Xylem fibers, and Xylem parenchyma. FUNCTION: Transports water and minerals from the roots to the leaves. Support and strengthening.

XYLEM

PHLOEM Consist of sieve-tubes and companion cells. The sieve-tubes form a continuous tube, they have cytoplasm but no nuclei. They have sieve plates between cells. The companion cell has a nucleus that controls both cells because they are connected by plasmodesmata. It also has other tissue: Phloem fibers and phloem parenchyma FUNCTIONS: Transports sucrose and other organic substances, including hormones, from the leaves to the roots. Support and strengthening.

METHODS TO STUDY CELLS The microscope is an instrument designed to observe objects too small to be seen with the naked eye. The human eye cannot distinguish objects much smaller than 0.1mm. The microscope act as an extension of the eye, allowing one to see smaller objects.

ELECTRON MICROSCOPE The electron microscope was developed in the late 1940’s and soon used in the study of cells. Much more detail can be seen under an electron microscope. It can magnify parts of cells at least 300 000 times.

SCANNING ELECTRON MICROGRAPH TRANSMISSION ELECTRON MICROGRAPH