Plant physiology

Plant Physiology – Study Notes

For B.Pharm Admission – Biology (Beginner Level)

1. What is Plant Physiology?

• The study of how plants work inside.
• Think of a plant as a house that drinks, eats, and grows.

2. Core Functions of a Plant (The “House” Analogy)

3. Water Transport – “The Plumbing System”

1. Root Water Uptake

   • Roots pull water from soil.
   • Tiny “suck cups” called root hairs increase surface area.

2. Xylem (Water Pipes)

   • Vertical tubes that carry water from roots to leaves.
   • Think of them as pipes that run up the house.

3. Transpiration – Water Loss

   • Water evaporates through stomata.
   • It pulls more water upward, like a vacuum.

Mini Example
An apple tree drinks water through its roots. The water travels up the trunk (xylem) to the leaves. As leaves lose water to air, more water is pulled up, keeping the tree full and healthy.

4. Light Absorption – “The Kitchen Stove”

• Leaves have a green pigment called chlorophyll.
• Chlorophyll captures sunlight and turns it into chemical energy.
• The energy is stored as sugar (glucose).

Mini Example
A sunflower’s leaves shine green. Sunlight hits the leaves, and the plant creates sugar that feeds the whole plant—just like a stove turning sunlight into a warm meal.

5. Gas Exchange – “Windows for Fresh Air”

• Stomata are tiny pores on leaf undersides.
• They open to let CO₂ in (needed for photosynthesis).
• They close to reduce water loss when it’s hot or dry.

Mini Example
A tomato plant’s leaves open their stomata in the morning to breathe in CO₂, then close them in the afternoon to keep water inside.

6. Nutrient Uptake – “Grocery Shopping”

• Roots absorb minerals (nitrogen, potassium, etc.) from soil.
• These minerals help build proteins, flowers, and fruit.

Mini Example
A pea plant pulls nitrogen from the soil to make the green leaves it needs for growth.

7. Growth & Development – “Building New Rooms”

• Cell division adds new cells; cell elongation stretches them.
• Plant hormones (auxins, gibberellins, cytokinins, ethylene) act like construction managers, telling cells when to grow or stop.

Mini Example
A carrot grows deeper into the ground because auxins help cells in the root elongate. When the carrot is ready, ethylene signals the fruit to ripen.

8. Stress Response – “Home Security System”

• When drought, cold, or pests attack, plants produce special chemicals.
• They close stomata, produce protective sugars, or release signals to neighboring plants.

Mini Example
If a leaf gets bitten by a caterpillar, the plant releases a bitter compound that makes the caterpillar taste bad, protecting the rest of the plant.

9. Summary

Key Takeaway
Plants are like smart houses: they drink water, cook food from sunlight, breathe in CO₂, grow new rooms, and protect themselves from threats. Understanding these processes helps pharmacists know how plant medicines are produced and how they work inside the body.

Quick Quiz

1. What part of the plant acts like a plumbing system?
   Answer: Roots and xylem.

2. Which hormone is responsible for plant fruit ripening?
   Answer: Ethylene.

3. Why do stomata close in hot weather?
   Answer: To reduce water loss through transpiration.

Feel confident! You’ve covered the basics of plant physiology in a simple, everyday language.