Students can go through AP Inter 2nd Year Botany Notes 4th Lesson Photosynthesis in Higher Plants will help students in revising the entire concepts quickly.
AP Inter 2nd Year Botany Notes 4th Lesson Photosynthesis in Higher Plants
→ Green plants carry out photosynthesis, a physiàochemical process by which they use light energy to drive the synthesis of carbohydrates.
→ It is the primary source of all food on earth. It is also responsible for the release of O2 into the atmosphere.
→ Co2 is required for photosynthesis, proved by Moll’s half leaf experiment.
→ Joseph Príestely in 1770 revealed the esssential role of air in the growth of green plants.
→ Jan Ingenhousz showed that an aquatic plant in bright sunlight releases air bubbles to be those of oxygen.
→ Julius Von Sachs provided evidence for the production of Glucose in the green parts of the plant.
→ The O2 released during photosynthesis is from water.
→ Photosynthesis occurs in all green parts of the plant.
→ The membrane system (grana) is responsible for trapping he light energy and also for the synthesis of ATP and NADPH.
→ In storma, enzymatic reactions incorporate CO2 into the plant 1eadin to synthesis of sugar.
→ The colour that we see on the leaves is due to four pigments. They are chlorophyll a, chlorophyll b, xanthophylls and carotenoids.
→ Graph showing rate of photosynthesis at different wavelengths is called action spectrum.
→ Graph showing light absorption by pigments at different wavelengths is called absorption spectrum.
→ Chlorophylla is the chief pigment associated with photosynthesis.
→ Chlorophyll b, xanthophylls and carotenoids are called accessory pigments.
→ Cyclic photophosphorylation involves only PS I.
→ In Non-cyclic photophosphorylation both PS I and PS II are involved.
→ Water molecules split in the presence of light and release electrons, protons and oxygen.
2H2O → 4H+ + O2 + 4e–
→ ATP synthesis is linked to development of a proton gradient across a membrane.
→ ATP and NADPH are used to drive the processes leading to the synthesis of food (sugar) – Biosynthetic phase.
→ The plants in which product of CO2 fixation is a C3 acid (PGA) i.e., the C3 pathway and those in which the first product is a C4 acid (OAA) i.e., the C4 pathway.
→ Calvin cycle can be described in three stages, (a) carboxylation (b) reduction (c) regeneration.
→ For every CO2 molecule entering the Calvin cycle, 3 molecules of ATP and 2 molecules of NADPH are required.
→ C4 plants have a special leaf anatomy, they tolerate higher temperatures, they show a response to high light intensities, they lack a process called photorespiration and have greater productivity of Biomass.
→ Crassulacean acid metabolism is an alternative to the C3 and C4 pathway of CO2 fixation found in plants in dry and hot climates.
Ex : Cacti.
→ Light dependent release of CO2 and uptake of O2 by the green tissue of particularly C3 plants is called Photo respiration.
→ Green plants carry out ‘Photosynthesis’.
→ During this process carbondioxide from the atmosphere is taken in by leaves through stomata.
→ During photosynthesis plants use light energy and synthesise carbohydrates.
→ Ultimately all living organisms on the earth depend on plants either directly or indirectly.
→ Photosynthesis provides food to all, as well it releases oxygen into the atmosphere.
→ Chloroplasts present in mesophyll cells of leaves-are responsible for CO2 fixation.
→ Pigments present in chloroplasts are Chi ‘a’, Chi ‘b’, xanthophylls and carotenoids.
→ There are two photosystems in Chl ‘a’, (i) PSI (ii) PSII.
→ Assimilatory power is generated in ATP and NADPH during photochemical reaction.
→ This power is utilised in dark reaction for the synthesis of carbohydrates.
→ Dark reaction occurs on stroma of chloroplast.
→ Based on the first stable product in dark reactions, two pathways are identified.
→ They are (i) Calvin cycle (C3 cycle) (ii) Hatch and Slack cycle (C4 cycle).
→ Calvin cycle includes carboxylation. reduction and regeneration.
→ First stable compound in Calvin cycle is PGA (a C3 compound).
→ C4 cycle operates in two photosynthetic cells-Mesophyll and bundle sheath cells.
→ First stable product in Hatch and Slack pathway is OAA (a C4 compound).
→ Phosphoenol pyruvate (PEP) is the primary CO2 acceptor in C4 plants. [NEET 2017]
→ The process which makes major difeence between C3 and C4 plants is glycolysis. [2016]
→ Water soluble pigments found in plant cell vacuoles are anthoeyanins. [NEET-2016]
→ In a chloroplast, the highest number of protons are found in lumen of thylokoids. [2016]
→ Chromatophores take part in photosynthesis. [NEET-2015]
→ In photosynthesis, the light-independent reactions take place at stromal matrix. [NEET-2015]
→ In light reaction, Plastoquinone facilitates the transfer of electrons from PS-II to Cytb6fcomplex. [NEET-2020]
→ Manganese is essential for photolysis of water. [2016 PMT]
→ Best defined function of manganese in green plants is photolysis of water. [2016 PMT]