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plants
🌱 Plant Tissues and Organs
Plants are made up of tissues that work together to perform specific functions.
Tissue | Function |
|---|---|
Epidermal tissue | Covers the surface; protects the plant. Transparent to let light through (especially upper epidermis). May have a waxy cuticle to reduce water loss. |
Palisade mesophyll | Carries out photosynthesis. Lots of chloroplasts. |
Spongy mesophyll | Contains air spaces to allow gases to diffuse (CO₂ and O₂). |
Xylem | Transports water and mineral ions from roots to leaves. Made of dead cells. |
Phloem | Transports dissolved sugars from leaves to rest of the plant. Made of living cells. |
Meristem tissue | Found at growing tips (roots and shoots). Can differentiate into any type of plant cell. |
🍃 The Leaf – Structure and Adaptations
Part | Adaptation |
|---|---|
Broad surface | Large surface area to absorb more light. |
Thin | Short diffusion path for gases. |
Chloroplasts in palisade cells | Absorb sunlight efficiently. |
Stomata | Allow gas exchange – CO₂ in, O₂ out. |
Guard cells | Control the opening and closing of stomata. |
💧 Transport in Plants
🔹 Xylem – Water Transport (Transpiration Stream)
Water and minerals travel up from roots to leaves.
Water evaporates from leaves via stomata (called transpiration).
This pulls more water up through the plant.
🔹 Phloem – Sugar Transport (Translocation)
Sugars made in the leaves (photosynthesis) are moved to the rest of the plant for energy or storage.
This process is called translocation.
Transport goes up and down the plant.
🌬 Transpiration
🔹 What is it?
The loss of water vapour from the leaves through stomata.
🔹 Steps:
Water evaporates from cells inside leaf.
Water vapour diffuses out through stomata.
More water is pulled up from xylem (transpiration stream).
🔹 Factors That Increase Transpiration:
Factor | Why it increases transpiration |
|---|---|
Light | More photosynthesis → stomata open. |
Temperature | More evaporation. |
Wind | Removes water vapour, increasing diffusion. |
Low humidity | Dry air increases evaporation rate. |
🧪 Required Practical: Measuring Transpiration (Potometer)
Measures water uptake by a plant.
Use a capillary tube and air bubble to measure how far the bubble moves.
Conditions like light, heat, humidity, and wind can be changed to test effects.
NoteStudied by 22 peopleNoteStudied by 19 peopleNoteStudied by 161 peopleNoteStudied by 60 peopleNoteStudied by 9 peopleNoteStudied by 257 people