Plant Nutrition
Photosynthesis
def (photosynthesis) - Is a process in which plants synthesize carbohydrates
from raw material using energy from light
Raw Materials
Water - Roots absorb water from the soil and transport it to the leaves
through the xylem tissue.
Minerals - Plants take in the minerals dissolved in water through active
transport.
Magnesium - Its a part of chlorophyll, its deficiency is called
chlorosis.
Nitrate - Helps in making protein (Growth of the plant)
Carbon dioxide - Plants take in carbon dioxide from the atmosphere
through their stomata.
Requirements
Light energy - Sunlight or artificial light provides the energy for
photosynthesis. (blue - red)
Chlorophyll - It is the green pigment in the palisade mesophyll cells of
the leaf. It traps light energy and passes it on to the raw materials.
Products of Photosynthesis
Glucose - It is the main product of photosynthesis. It is used by the plant
in the following ways:
It can be used as a substrate for respiration.
It can be converted into starch and stored in tubers and seeds.
It can be converted into cellulose and used in the formation of cell
wall.
It can be converted into fructose or sucrose and stored in sweet
fruits. It can also be used in the production of nectar.
Oxygen - It is the by product of photosynthesis. It is released into the
atmosphere through the stomata. This oxygen is used by plants and
animals for respiration.
Site of Photosynthesis
It takes place in the leaves of plants.
It can also take place in the green stems, sepals and fruits.
Leaf Structure
Epidermis - It consists of a layer of cells arranged without any intercellular
spaces. Both the upper and lower epidermis have stomata but the lower
epidermis has more stomata than the upper epidermis to prevent the loss of
water through evaporation.
Cuticle - Waxy and waterproof layer which makes the leaf waterproof and
prevents infections.
Mesophyll tissue - They are of 2 types: Palisade mesophyll and spongy
mesophyll.
Palisade mesophyll - It is the upper portion of the mesophyll tissue, it
comprises of 2-3 layers of closely packed rectangular cells which have
abundant chlorophyll.
Spongy mesophyll - It is the lower portion portion of the mesophyll
tissue, it comprises of loosely packed circular cells with a lot of air
cavities in between them.
Vascular bundle - It contains xylem and phloem which conduct water
and food.
Structure of Stomata
They are found in the epidermal layer of leaves, and other green parts of
the plant.
They help in the gaseous exchange between the plant and the
atmosphere.
Guard cells - They regulate the size of the pore. They have a thick inner
wall and a thin outer wall. When they absorb water the thin outer wall
expands pulling the inner wall along with it. This causes the stomata
pore to expand.
Subsidiary cells - They are soft allowing the guard cells to expand and
contract without any air cavities in between.