Photosynthesis (part-4) - photosynthesis in higher plants, Biology, Class 11 PDF Download

​HETEROTROPHIC PLANTS NUTRITION - photosynthesis in higher plants, Biology, Class 11

HETEROTROPHIC PLANTS NUTRITION

•  Heterotrophs – Heterorophic plants are of following types –

[A] Parasites –

(1) Total stem parasites – Cuscuta or dodar (totally depend)

(2) Partial stem parasites – Loranthus, Viscum (depend on host for H₂O & minerals)

(3) Total root parasites – Members of Rafflesiaceae, Balanophoraceae & Orobanchaceae (totally depends on host)

(4) Partial root parasites – Santalum album & Striga.

[B] Insectivorous plants – These are green plants but of insectivorous habits which develop, due to deficiency of nitrogen, because they grow on N₂–deficient places (Swampy places).

(1) Nepenthes or pitcher plant – Found in north eastern parts of India (Endangerd).

(2) Utricularia or bladderwort – hydrophyte and pollution Indicator.

(3) Drosera or Sundew

(4) Pinguicula or butterwort.

(5) Dionaea or venus fly trap.

(6) Saracenia or pitcher plant with symbiotic bacteria.

(7) Aldrovanda (Water flea trap)

(8) Genlisea (Lobster pot trap) [C] Saprophytes – Non green plants, which depend on dead organic matter – Monotrapa (Indian Pipe) Neottia (Birds eye nest) (Dischidia is a pitcher plant but not insectivorous).

SPECIAL POINTS

•  "Photosynthesis is a photo–biochemical process, in which organic compounds are synthesized from the inorganic raw materials (H₂O & CO₂) in presence of light energy and pigments (chl.) gas–oxygen evolved as byproduct."

•  First true & oxygenic photosynthesis started in cyanobacteria (BGA).

•  Roots of Tinospora and Trapa are photosynthetic.

•  Modern view about photosynthesis is conversion of light/radiant energy into biochemical or potential energy.

•  Absorption spectrum for photosynthesis in visible light is blue & red wavelength.

•  Action spectrum is red & blue light in which rate of photosynthesis is higher. (But rate of photosynthesis is highest in white light than monochromatic light).

•  Function of accessory pigment carotene is – . Converts elementary or nasent oxygen to molecular/gaseous O₂.

1. 

2. . Protects photooxidation (photodamaging) of pigment system. . Precursor of vit.–A.

3. . Oxidation to form ABA hormone in guard cells.

•  Chlorophyll pigment soluble in organic solvents like acetone, ether etc. (anthocyanin is non photosynthetic water soluble pigment, which present in vacuole).

• Chloroplast in bundle sheath of Burmuda grass is also granal type.

•  Photolysis of water occurs at +0.8 E°

•  In cyanobacteria (BGA), photosynthesis occurs on chlorosomes or lamellisome or carboxysome.

•  PS–I is strong reductant as PS–I has good ability to reduce NADP+, while PS-II is a strong oxidant, because it has extreme power of oxidation & photolysis of water molecule.

•  264 gm. CO₂ and 216 gm. water produced, 108 gm. water, 192 gm. O₂ and 180 gm. glucose.

•  Annual production of photosynthesis is 170 billion tones of carbohydrate.

•  Wilmott’s bubbler apparatus proves that oxygen is evolved during photosynthesis.

•  Cytochromes are Iron – porphyrin protein discoverd by MacMunn (termed by Keilin).

•  Pigments except chlorophyll, presents in Quantasomes are called as accessory or antenna pigment of light harvesting complex (LHC).

•  Electroosmotic theory - By Spanner and Jones for translocation of sugars.

•  Chollet and Ogren (1975) - Recognised 3 categories of C₄ plants.

(i) Maize and Sugarcane type : In this category malate transported to bundle sheath cells and its decarboxylation gives CO₂ for C₃ cycle.

(ii) Panicum and Chloris type :- In this category malate transported into bundle sheath cells, but this changes into oxaloacetate, which gives CO₂ for C₃ cycle.

(iii) Atriplex type :- In this category the aspartate transported into bundle sheath cells, where it changes into malate, which provides CO₂ for C₃ cycle.

•  Mg++ required for Rubisco & PEPcase

•  Ist formed unstable 6-C compound during Calvin cycle is carboxy ketoribitol biphosphate.

•  Significance of photosynthesis – Photosynthesis is vital process for life on planet earth as it is the only process, that links the physical and biological world by conversation of solar energy into organic matter, which make bulk of the dry matter of any organism.

Presence of O₂ in the atmosphere is also an outcome of photosynthesis. This oxygen is helpful to living organisms in two ways :

1. Oxidative break down of organic food matter (respiration)

2. Making ozone (O₃), in outer layer of atmosphere, which helps in stopping the highly destructive U.V. rays.

•  Efficiency of photosynthesis – One quantum of red light = 47.6 Kcal (One red photon or quantum = 47.6 Kcal) One glucose = 686 Kcal. (1 CH2O = 114.3 Kcal) 8 Quantum × 47.6 Kcal = 381 Kcal energy require for fixation of one CO2