RBSE Class 11 Biology Notes Chapter 13 Photosynthesis in Higher Plants

These comprehensive RBSE Class 11 Biology Notes Chapter 13 Photosynthesis in Higher Plants will give a brief overview of all the concepts.

RBSE Class 11 Biology Chapter 13 Notes Photosynthesis in Higher Plants

→ All green plants synthesize their own food and they are called producers.

→ Photosynthesis is a process in which all green parts of the plant prepare carbohydrates with the help of CO₂ and water in the presence of sun light. Oxygen is released as by product.

→ Von Helmont was explain first to that plants obtain their food only from water.

→ Joseph Priestley demonstrated that plants purify the foul air.

→ Jean Senebier proved that plants absorb carbon dioxide from air and release O₂.

→ Julius Robert Mayer in 1845 discovered that green plants store light energy in the form of chemical energy.

 

→ The oxygen released from photosynthesis comes from water not from CO₂.

→ According to modern concept, the photosynthesis is a oxidation-reduction process in which water oxidises to form O₂ and CO₂ reduces to form sugar.

→ In higher plant, there are two phases of photosynthesis:

• Light dependent reaction or Hill reaction.
• Dark reaction or Blackman reaction.

→ Photochemical reaction takes place in grana of chloroplast in the presence of sunlight, here photolysis of water takes place and ATP and NADPH2 are formed. In this process O₂ is released.

→ Photosynthetic plants have pigments to absorb light energy. These pigments are found in chloroplasts. The pigments which are present outside do not take part in photosynthesis. Photosynthetic pigments are mainly of three types:

• Chlorophyll,
• Carotenoids and
• Phycobillins.

→ In light reaction of photosynthesis, two photo acts are worked photo act-I which has pigment system-I and photo act-II which has pigment system-II.

→ The process of ATP formation from ADP and inorganic phosphate in the presence of sunlight is called photophosphorylation. It is of two types: cyclic photophosphorylation and non-cyclic photophosphorylation.

→ The dark reaction of photosynthesis does not require light, i.e., it takes place both in presence and absence of light. In this process ATP and NADPH2 obtained from light reaction are used in the synthesis of carbohydrates after reducing CO₂.

→ Three forms of dark reaction are known, they are:

1. Calyin cycle
2. Hatch and Slack cycle and
3. CAM cycle.

→ Calvin-Benson cycle is also called C₃ cycle. The plants in which this cycle is found are called C₃ plant because in these plants first stable compound of CO₂ fixation is phosphoglyceric acid (PGA) a three carbon compound.

→ Hatch and Slack cycle is also called C₄ cycle. The plants in which it found are called C₄ plants because in these plant the first stable compound of CO₂ fixation is formed 4-C compound oxaloacetic acid (OAA).

→ The leaves of C₄ plants such as sugarcane, maize etc., possess special anatomy called Kranz anatomy.

→ The CAM cycle of photosynthesis is found in various types of succulent plants such as Kalanchoe, Sedum etc. In these plants stomata open at night and close during the day. These plants accumulate CO₂ in sufficient amount as carbonic acid at night and during day time they reduce CO₂ to carbohydrates.

→ The process of photosynthesis is affected by various external (environmental) and internal factors.

→ Photosynthesis: An anabolic process in which solar energy is converted into chemical energy in the form of food.

→ Chloroplast: A cell organelle of green plants. Plastid with chlorophyll.

→ Grana: Structure found in chloroplast made of lamellae. The site of photosynthesis.

→ Stroma: Extra lamellar space of chloroplast. The site of dark reaction of photosynthesis.

→ Carbon assimilation: Use of CO₂ to form carbohydrates.

→ Photolysis: The spliting of water molecule into H⁺ and OH^- by sunlight.

→ Quantasome: The unit of absorbed light by chlorophyll molecules.

→ Spectrometer: Light measurement device.

→ Kranz Anatomy: Internal structure of leaves of C₄ plants.

→ Photorespiration: The process of releasing CO₂ under high concentration of O₂.

→ RUBISCO: An enzyme which acts as carboxylase and oxygenase.