Types of Plant Organs • Vegetative organs: • Roots • Leaves • Stems • Reproductive organs: • Flowers • Fruit
Plant Body Systems • The plant body is organized into a root system and a shoot system: • Root system is generally below ground. • Shoot system consists of vertical stems, leaves, flowers, & fruit that contain seeds.
Roots • Absorb water & minerals • Anchor the plant • Storage (Some Roots)
Types of Roots Taproot Prop Root Fibrous Root
TAP ROOT • Seen in dicots. • The direct elongation of the radicle leads to the formation of primary root which grows inside the soil. • It bears lateral roots of several orders that are referred to as secondary, tertiary, etc. roots. • The primary roots and its branches constitute the tap root system
FIBROUS ROOT • In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots. • These roots originate from the base of the stem and constitute the fibrous root system
ADVENTITIOUS ROOTS • In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious roots.
Regions of the Root • The root is covered at the apex by a thimble-like structure called the root cap. It protects the tender apex of the root as it makes its way through the soil. • A few millimetres above the root cap is the region of meristematic activity. The cells of this region are very small, thin-walled and with dense protoplasm. They divide repeatedly. • The cells proximal to this region undergo rapid elongation and enlargement and are responsible for the growth of the root in length. This region is called the region of elongation. The cells of the elongation zone gradually differentiate and mature. • The zone proximal to region of elongation, is called the region of maturation. From this region some of the epidermal cells form very fine and delicate, thread-like structures called root hairs. These root hairs absorb water and minerals from the soil.
Modifications of Root 1.STORAGE ROOTS: i) Adventitious roots become tuberous in sweet potato. ii)Tap root modified for storage become swollen with food material and depending on the shape of the storage roots , they are described as follows: a)CONICAL –Eg. Carrot b)FUSIFORM: Eg. Raddish c)NAPIFORM- Eg.Beetroot,turnip D)TUBROUUS-Eg. Mirabilis
Fleshy Tap Roots • Carrots, beets, and radishes are examples of plants forming fleshy tap roots. Carrots
Tuberous Roots • Sweet potato is an example of a tuberous root. A sweet potato is a tuberous root
Tuberous Roots • Dahlias are perennial bedding plants that form tuberous roots. Dahlia
2. STILT ROOT • These are adventitious roots which arise in cluster from the basal nodes just above the ground Eg. Maize, sugar cane, pandanus. Pandanus
Prop roots such as these inspired flying buttresses. Pandanus utilis - screw pine
Prop Roots • Massive pillar like outgrowths of aerial branches , which grow downwards and become large and woody. • Banyan
Pneumatophore • Rhizophora plants have pneumatophores. • They are negatively geotrophic. Grow upwards • Does respiration Mangrove plants
Stems • Stems are the part of the plant from which the shoots and buds arise. • Arises from plumule. • Stems (and leaves) are the most conspicuous and diverse organs of plants: • Trunk of a tree • Stem of a flower
Structure of Stems • A stem is a collection of integrated tissues arranged as nodes and internodes. • Nodes: regions where leaves attach to stems • Internodes: parts of stems between nodes
Functions of Stems • Stems perform important functions: • Support leaves, flowers, & fruits • Produce carbohydrates • Store materials • Transport water and minerals • Protection/Defense • Anchorage
DIVERSE FORMS OF STEMS • UNDERGROUND STEMS • RHIZOME • BULB • CORM • TUBER • SUB-AERIAL STEMS • RUNNER,SUCKER,STOLON, OFFSET • AERIAL STEM • TENDRIL,THORN,PHYLLOCADE,CLADODE.
Tubers • A tuber is an underground stem that stores food. • potato is a tuber because it has nodes (eyes) which produce new shoots. Potato is a tuber
Corms • A corm is a swollen, vertical stem with a papery covering. • Gladiolus and Crocus are examples of plants that form corms. Crocus corms
Bulbs • A shortened underground bud in which fleshy storage leaves are attached to a short stem. • Bulbs are rounded and are covered with paper-like bud scales, which are actually modified leaves! • Examples: • Onions • Garlic • Tulips • Daffodils
Rhizomes • Rhizomes are: • underground stems. • horizontally-growing. • produce shoots and adventitious roots. Iris rhizome
Runners • Horizontal, above ground stems that grow along the ground’s surface and are characterized by long internodes. • Buds develop along the stolon and give rise to new plants that root in the ground. • Examples: • Strawberry • Nut grass
SUCKER • It is a branch arising from the basal ans underground part of main stem • Grows horizontally for a short distance under the soil and emerges obliquely above the ground and bears a leafy shoot.
STOLON • It is a slender , lateral branch that arises from the base of the main stem. • Aerial branch arches downwards to touch the ground. • Eg. Jasmine.
OFFSET • A lateral branch with short internodes and each node bearing a rosette of leaves and a tuft of roots is found. • Eg. in aquatic plants like Pistia and Eichhornia
Tendrils • Stem tendrils which develop from axillary buds, are slender and spirally coiled and help plants to climb . • Examples: • gourds (cucumber, pumpkins, watermelon) • grapevines.
Thorns • Modified stems that protect plants from grazing animals. • Example Citrus, Bougainvillea
Phylloclade • Phylloclade are: • Above ground stems. • Grow horizontally or vertically. • Do not have leaves • Leaves are modified to form spine • They store water and are succulent. • Are green and perform photosynthesis. • Cactus, opuntia .
Leaves A plant’s “solar panels” …
Leaves • The leaf is a lateral, generally flattened structure borne on the stem.
It develops at the node and bears a bud in its axil. The axillary bud later develops into a branch. • Leaves originate from shoot apical meristems and are arranged in an acropetal order.
Basic Leaf Structure • Most leaves are flat with a transparent epidermis. • Most leaves are composed of two parts: • Blade: the broad, flat portion of the leaf • Vein • Midrib • Petiole: the stalk that attaches the blade to the stem. • Stipule (leaf outgrowths)
Leaves Vary Greatly in Form • Leaves are the most variable plant organ—so much that botanists developed terminology to describe their shapes, margins, vein patterns, and attachment methods. • Leaves may be round, needle-like, scale-like, cylindrical, heart-shaped, fan-shaped, or thin and narrow. • Vary in size from >20 meters (Raffia palm) to microscopic (duckweed).