Lamina = 🌱Section of a leaf which is wide and flat with large surface area for absorption of sunlight.

Petiole = 🌱Section of a leaf that joins lamina to the stem of a plant.

☘️ Cuticle

🟢it's a waxy and waterproof. Its transparent which allows sunlight to pass through it.

☘️Upper Epidermis

🟢located at the upper surface of the leaf "under the cuticle".

🟢It's transparent so the light can pass through it

🟢this layer does not contain chloroplast.

☘️Lower Epidermis

🟢located at the lower surface of the plant.

🟢this layer consists of stomata

🟢each stomata is guarded by a pair of guard cells

☘️Palisade Mesophyll

🟢arranged vertically and closely packed to receive max light exposure.

🟢the cells are the sites for photosynthesis

🟢contains a lot of chloroplasts

☘️Spongy Mesophyll

🟢Irregular shaped of cells which contains chloroplasts.

🟢Loosely arrangement of spongy mesophyll cells

🟢has less number of chloroplasts than palisade mesophyll

☘️Vascular Bundle

🟢Xylem = -transports water and mineral salts -xylem walls are lignified and thickened to provide mechanical support to the plants.

🟢Phloem = -transports organic substances

📗In the presence of light during daytime, photosynthesis ✅ occurs in guard cells.

📗glucose is produced and energy is generated for active transport

📗potassium ion is pumped into guard cells from the surrounding epidermal cells by active transport

📗this causes a reduction of water potential in the guard cells

📗water diffuses into guard cells by osmosis

📗guard cells become turgid

📗the guard cells curve outwards

📗the stoma opens

📕at night, photosynthesis does ❌ not occur in guard cells

📕glucose is not ❌ produced and active transport does not occur in guard cells

📕potassium ions diffuses out from guard cells into the surrounding epidermal cells

📕water potential in the guard cells increases

📕water diffuses out from guard cells by via osmosis

📕guard cells becomes more flaccid

📕guard cells are less curvy

📕the stoma closes

plants obtain essential gasses through leaves

plants need oxygen for respiration

plants need carbon dioxide for photosynthesis

🧪transpiration is a process which water is lost from plant to the environment

🧪water is lost in the form of water vapour through the stoma and lenticels of plants

🦠Why does Transpiration rate increases ?

it increases when...

🧪increases in light intensity

🧪increases in temperature

🧪increases in air movement

🧪decreases in air humidity

🦠Why is Transpiration required in Plants?

🧪plant roots absorb water and mineral salts from soil

🧪water absorbs heat energy from leaves

🧪then evaporates as water vapour to give a cooling effect

🏝roots absorb water from the soil

🏝The xylem transports water upwards in the plant stem

🏝leaf veins transport water to the leaves

🏝water evaporates to the atmosphere through stomata

💜the relative air humidity is inversely proportional to the transpiration rate

💜the lower the air humidity of the surrounding atmosphere, the faster the water vapour escapes from the stomata

💜thus, the rate of transpiration becomes higher

💙increase in temperature, will increase the kinetic energy of water molecules

💙thus, increasing the rate of transpiration

💚the faster the air movement, the faster the rate of transpiration

💚the wind speed is directly proportional to the transpiration rate

💚the movement of air carries away water molecules that have been diffused out from the leaves

🍃this is the first stage called the light-dependent where it produces oxygen and water molecules

🍃the light-dependant reactions occurs in the thylakoid

🍃thylakoid is a membrane

🍃During the light-dependant reactions, photosynthetic pigments on the surface of thylakoid absorb light energy

🍃Light energy is used to excite electrons in the chlorophyll pigment to a higher level

🍃the excited electrons will finally be accepted by the final electron carrier, namely NADP+

🍃simultaneously, light energy will also be used to breakdown water molecule to hygrogen ions (H+) and hydroxyl ions (OH-) by photolysis of water

🍃NADP+ combines with hydrogen ions to form NADPH

🍃hydroxyl ion loses an electron to form oxygen and water

🍃the products of light-independent reactions are ATP, NADPH, and oxygen.

🍃ATP and NADPH then enter the light-independant reactions, whereas oxygen is released to the atmosphere.

🍃the second stage is called light-independent reactions

🍃The light-independent reactions occur in stroma

🍃during the light-independent reactions, carbon dioxide binds to the 5-carbon organic compound

🍃NADPH and ATP produced from the light-dependent reactions reduce the 6-carbon organic compound to a glucose monomer

🍃glucose monomer is then condensed to form starch molecule which is kept in the stroma as granules

🌙Both occur in chloroplast

🌙Both are catalysed by enzymes

💌carbon dioxide is needed to synthesize glucose in light-independent reactions

💌as the carbon dioxide increases, the photosynthesis rate increases until it reaches saturation point

💌after the saturation point, increases in the concentration of carbon dioxide no longer increase the rate of photosynthesis

💌limiting factors such as light intensity and temperature limit the increase in photosynthesis rate after the saturation point

💌photosynthesis rate can be increased by increasing light intensity

💌however, if the light intensity is too high, the stomata will close to reduce the water loss through transpiration. This prevents carbon dioxide from entering the leaf, which subsequently decreases photosynthesis rate

💌Light energy is needed for light photolysis and to activate chlorophyll in light-dependent reactions

💌as light intensity increases, the photosynthesis rate increases until it reaches the saturation level at point P (Graph (i))

💌after point P, the increase in light intensity no longer causes the increase in the photosynthesis rate

💌limiting factors such as carbon dioxide and temperature had limited the increase of photosynthesis rate

💌photosynthesis rate can be increased by increasing concentration of carbon dioxide or temperature (graph (ii))

💌when light intensity is too high, photosynthesis rate slows down because chlorophyll pigments are damaged by ultraviolet rays

💌any changes in temperature will affect the photosynthesis rate because light-independent reactions are catalysed by enzymes

💌as the temperature increases, the rate of photosynthesis will also increase until the optimum temperature. The optimum temperature of most plants is between 25°C to 30°C

💌at higher temperature than the optimum temperature, photosynthesis rate decreases because the enzymes are denatured

🌈light colours play and important role in photosynthesis

🌈Light spectrum consist of seven colours in a certain sequence which is violet, indigo, blue, green, yellow, orange and red.

🌈each colour has a different wavelength

🌈Plants only use a few types of light colours in photosynthesis

🌈photosynthesis rate is highest in blue light, followed by red light

🌈all of red light is absorbed by chlorophyll

🌈the blue light is absorbed by carotenoid pigments before being transferred to the chlorophyll

🌈these two lights have enough amount of energy to excite electrons in the light-dependent reaction

🌈green light is not absorbed by plants, therefore green light is not used in photosynthesis

💐Both processes take place in living organisms

💐Both processes involve the uptake and release of gases