Biology class notes for 10th grades, or lower/higher. Covers photosynthesis, wilting, etc.
Approved and closely followed to the A-level Cambridge Examinations
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Plant Nutrition - Notes
Autotrophic and Heterotrophic Nutrition
Autotrophs vs Heterotrophs
Type Definition
Organism that synthesizes complex organic compounds from simple inorganic raw
Autotroph
materials; also called producer
Organism that ingests other organisms to obtain energy and body-building materials;
Heterotroph
also called consumer
Photosynthesis
Photosynthesis is a process whereby light energy is absorbed by the chlorophyll and
converted into chemical energy, which is then used in the synthesis of organic molecule,
simple sugar (glucose); from inorganic materials, water and carbon dioxide. Oxygen gas is
released in the process.
Word equation for photosynthesis
Water + Carbon Dioxide → Glucose + Oxygen
Chemical equation for photosynthesis (Rmb to write light energy & chlorophyll above
arrow)
6 H2O + 6 CO2 → C6H12O6 + 6 O2
Photosynthesis and cellular respirations are the reverse reactions of each other.
Products of photosynthesis are glucose (most impt), oxygen and water.
Importance of photosynthesis
Photosynthesis allows producers to convert light energy and inorganic raw materials
into chemical energy and organic molecules, which are transferred up the food chain
when they are consumed.
Photosynthesis also produces oxygen into the air for cellular respiration by most living
things.
Plant Nutrition - Notes 1
, Plants which are not eaten but have died millions of years ago can have their remains
be converted to fossil fuels; They are burned in the present to release energy stored in
them.
External features of a dicot leaf
Part Characteristics Functions
Holds lamina away
Petiole ↑ exposure to sunlight
from stem
1. Max absorption of sunlight 2. Rapid diffusion of CO2 into
1. Large flat surface
Lamina inner mesophyll cells; sunlight to penetrate into inner cells
area 2. Thin
more easily
- Net venation, mid-rib - Xylem transports water & mineral salts into cells in the
branching off to many lamina - Phloem transports manufactured sugar from leaves
Leaf veins
veins - Contains to other parts of the plant Transported as sucrose as it's in
vascular bundles a less reactive form)
Arranged in a regular
Leaf pattern around the Ensure leaves aren't blocking one another from sunlight, and
arrangement stem (e.g. opposite, each leaf receives max amt of sunlight
whorled, alternate)
Internal structures of a dicot leaf
Structure Characteristics Functions
1. Reduce water loss thru evaporation;
Cuticle 1. Waxy layer 2. Transparent prevent entry of microorganism 2. Allow
sunlight to penetrate to the mesophyll
More stomata are found on the lower
Upper & - Single layer of closely packed cells - No
epidermis to reduce rate of water loss thru
lower chloroplasts (besides guard cells) - Secretes
evaporation (temp on lower epidermis is
epidermis cuticle - Stomata: Upper < Lower
lower)
Max absorption of sunlight (main site of
- Few layers of closely packed long
Palisade photosynthesis 80% Cytoplasmic
cylindrical cells - Contains many
mesophyll streaming for efficient distribution of
chloroplasts - Cytoplasmic streaming
sunlight among chloroplasts
1. Irregularly shaped cells that is loosely
Spongy packed 2. Numerous large intercellular air 1. Rapid diffusion of gases inside the leaf
mesophyll spaces - Contains fewer chloroplasts than 2. Gaseous exchange
palisade mesophyll cells
Plant Nutrition - Notes 2
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