Understanding Plant Tissues, Reproduction, and More
Plant Tissues
Plant tissues are groups of similar cells performing specific functions in plants. They are broadly classified into dermal, ground, vascular, and meristematic tissues.
1. Dermal Tissue
Dermal tissue forms the outer protective covering of the plant. It consists of:
- Epidermis: Covers the external parts of herbaceous plants. Epidermal cells secrete a waxy cuticle, protecting against water loss. It is the outermost layer of the primary plant body, covering roots, stems, leaves, floral parts, fruits, and seeds. Typically one layer thick with a cuticle, composed mostly of unspecialized parenchyma and sclerenchyma cells.
- Periderm: The outermost layer of stems and roots in woody plants, such as trees. It replaces the epidermis in plants undergoing secondary growth. It is a multilayered structure that protects the plant from injuries.
2. Ground Tissue
Ground tissue comprises the bulk of the plant and is composed of parenchyma cells. It synthesizes organic compounds and supports the plant by storing produced products.
3. Vascular Tissue
Vascular tissue is responsible for the transport of water, hormones, and minerals throughout the plant. It contains transfer cells and fibers, in addition to xylem, phloem, cambium, and other conducting cells. These tissues are located in the veins of the leaves.
- Xylem: Also known as water-conducting cells. These are dead, hollow cells that transport water and dissolved nutrients from the roots to all parts of the plant in an upward direction.
- Phloem: Transports dissolved organic food materials (sugars) from the leaves to all parts of the plant. These are live cells, lacking a nucleus and other organelles. They transport nutrients in a downward direction and are also called sugar-conducting cells.
4. Meristematic Tissues
Meristematic tissues are groups of cells with the ability to divide. Characteristics include:
- Small cells with thin cell walls.
- Cells with large nuclei.
- Cells with very small vacuoles and lacking intercellular spaces.
They have tiny pores, which allow essential carbon dioxide in and waste gases out, important for nutrition and excretion.
Roots
Roots provide anchorage for the plant, preventing it from blowing away or falling over. They are important for nutrition, providing a large surface area to help take in water and minerals from the soil.
Plant Reproduction
1. Sexual Reproduction in Plants
The flower is the reproductive part of a plant, where male and female gametes are produced.
Pollination and Fertilization
To form a zygote, male gametes in pollen grains must fuse with the egg in the ovule.
Pollination is of two types:
- Self-Pollination: Pollen transfer takes place between the anther and stigma of the same flower.
- Cross-Pollination: Pollen transfer takes place between the anther and stigma of different flowers of the same plant or different plants of the same species.
Pollination takes place with the help of pollinators such as wind, water, insects, and birds.
Pollination is the transfer of pollen to the plant’s stigma, while fertilization is the joining of sperm and egg.
2. Asexual Reproduction in Plants
Asexual reproduction is the process through which an organism produces other organisms without the participation of more than one parent.
- Runner or Stolon: Produces buds that develop into new plants that are clones.
- Fragmentation: Small parts of the plant fall off onto the soil and grow into a new plant.
- Budding: Each bud grows up like a clone of the original plant.
- Gemmation: These are shed and dispersed to other areas, where they grow to produce new individuals.
- Vegetative Propagation: A part of the plant is taken and replanted in another place.