Plant Tissues: Structure, Functions, and Types
1. Dermal Tissue
– Consists of epidermis and periderm – Covers the external part of herbaceous plants – Composed of epidermal cells that secrete a waxy cuticle – Waxy cuticles protect plants against water loss
Epidermis
– Outermost layer of the primary plant body – Covers roots, stems, leaves, floral parts, fruits, and seeds – One layer thick with cuticle – Composed mostly of unspecialized cells (parenchyma and sclerenchyma)
Periderm
– Outermost layer of stems and roots of woody plants – Replaces epidermis in plants that undergo secondary growth – Multilayered structures – Protects the plant from injuries
2. Ground Tissue
– Composed of parenchyma cells – Synthesizes organic compounds and supports plants by storing produced products
3. Vascular Tissues
– Contain transfer cells, fibers, xylem, phloem, cambium, and other conducting cells – Specialized cells for transport of water, hormones, and minerals throughout the plant – Located in the veins of leaves
Xylem
– Water-conducting cells – Dead with hollow cells – Transport water and dissolved nutrients from roots to all parts of a plant – Transport nutrients upwards, from root to stem, leaves, and flower
Phloem
– Live cells that lack nucleus and other organelles – Transport dissolved organic food materials (sugars) from leaves to all parts of a plant – Transport nutrients downwards, from leaves to different parts of the plant – Also called sugar-conducting cells
4. Meristematic Tissues
– Group of cells with the ability to divide
Characteristics
– Very small cells with thin cell walls – Large nuclei – Very small vacuoles and lack intercellular spaces
Types of Meristems
– Apical meristems
Flower
The Female Reproductive Organs
– Pistil: Collective term for carpel(s) – Carpel includes: – Ovary (where ovules are produced) – Style (tube on top of the ovary) – Stigma (receives pollen during fertilization)
The Male Reproductive Organs
– Stamens: Male reproductive parts of flowers – Stamen consists of: – Anther (produces pollen) – Filament – Pollen contains male reproductive cells that fertilize ovules
1. Sexual Reproduction in Plants
– Flower is the reproductive part of a plant – Male and female gametes are produced by flowers
Pollination and Fertilization
– Male gametes in pollen grains must fuse with egg in the ovule to form a zygote – Pollination: Transfer of pollen grains from anther to stigma of a flower
Types of Pollination
– Self-Pollination: Pollen transfer between anther and stigma of the same flower – Cross-Pollination: Pollen transfer between anther and stigma of different flowers of the same plant or different plants of the same species
– Pollination agents: Wind, water, insects, birds – Pollination is a process only flowering plants undergo – Fertilization: Joining of sperm and egg
2. Asexual Reproduction in Plants
– Process through which an organism produces other organisms without participation of more than one parent
Types of Asexual Reproduction
– Runner or stolon: Stem portion that grows horizontally – Fragmentation: Small part of plant falls off and grows into a new plant – Budding: New plant develops from an outgrowth (bud) in the plant body – Gemmation: Small clumps of undifferentiated cells (gemmae) develop on the surface of a plant – Vegetative Propagation: Part of the plant is taken and replanted in another place – Reproduction takes place through vegetative buds of the plant