Roots are the underground parts of a flowering plant. In dicotyledonous plants, the primary root grows directly from the radicle and gives rise to lateral roots, forming a tap root system, as seen in mustard plants. In monocotyledonous plants, the primary root is short-lived and replaced by numerous roots originating from the stem base, forming a fibrous root system, like in wheat. Adventitious roots arise from parts other than the radicle, as seen in grass and banyan trees. The root system's main functions include water and mineral absorption, plant anchorage, food storage, and synthesis of growth regulators.
Did You Know?
Some plants, like mangroves, have specialized roots called pneumatophores that help in gas exchange.
Mnemonic:
Remember root functions with "AIMS": Absorption, Anchorage, Storage, Synthesis.
The root tip is covered by a root cap, protecting it as it grows through the soil. Just above the root cap is the region of meristematic activity, where cells divide rapidly. Above this is the region of elongation, where cells grow in length. The region of maturation, where cells differentiate, is proximal to the elongation zone. Root hairs in this region absorb water and minerals.
The stem is the ascending part of the plant axis, bearing branches, leaves, flowers, and fruits. It develops from the plumule of the embryo and consists of nodes and internodes. Stems perform multiple functions, including support, transport of water and nutrients, storage, and vegetative propagation.
Real-life Application:
The stems of plants like sugarcane and bamboo are economically significant for producing sugar and building materials, respectively.
NEET Tip:
Understand the difference between tap roots (dicots) and fibrous roots (monocots) for NEET questions.
Leaves are the primary sites of photosynthesis. A typical leaf consists of three parts: the leaf base, petiole, and lamina. The leaf base attaches the leaf to the stem and may have stipules. The petiole holds the blade to light, and the lamina is the expanded part with veins and veinlets.
Venation is the arrangement of veins in a leaf. Dicot leaves usually have reticulate venation, where veins form a network. Monocot leaves typically exhibit parallel venation, where veins run parallel.
Common Misconception:
Not all monocots have parallel venation; some, like certain types of grass, show reticulate venation.
Mnemonic:
"Simple leaves, single lamina; compound leaves, cut into leaflets."
Phyllotaxy is the arrangement of leaves on the stem. Types include:
Inflorescence is the arrangement of flowers on a floral axis. Major types are:
NEET Tip:
Recognize racemose (unlimited growth) vs. cymose (limited growth) inflorescences.
Real-life Application:
Inflorescence type can affect crop yield and harvesting techniques in agriculture.
Flowers are the reproductive units of angiosperms. A typical flower has four whorls: calyx, corolla, androecium, and gynoecium.
Common Misconception:
Not all flowers have all four whorls; some may lack one or more.
Mnemonic:
"Actino-radial, Zygo-bilateral."
Placentation refers to the arrangement of ovules within the ovary. Types include:
Real-life Application:
Understanding placentation helps in hybridization and breeding programs.
Link to Chemistry:
Photosynthesis involves chemical reactions converting light energy into chemical energy, connecting biology with biochemistry.