(a)State four modes of nutrition in plants. (b)Outline the process involved in the light and dark reactions of photosynthesis

Autotrophic or holophytic nutrition is a mode of nutrition by which green leaves or plants manufacture their food using atmospheric carbon dioxide and soil water as raw materials with sunlight as the source of energy. This type of autotrophic nutrition is the photosynthetic autotrophic nutrition.

Autotrophs are organisms that can manufacture their own food from the substances present in their surroundings with the help of light (photosynthesis) or chemical energy (chemosynthesis).

Producers are green plants that make use of sunlight to manufacture food from nutrients obtained from the soil. Strictly, the definition implies that autotrophs acquire carbon from inorganic sources such as carbon dioxide (CO2. Autotrophs are normally plants; they are as well known as "self feeders" or "primary producers".

The second type of autotrophic nutrition in plant is chemosynthetic nutrition or chemosynthesis: This is type of autotrophic nutrition where the energy required for the synthesis of food is derived from chemicals or inorganic compound instead of from light energy from the sun.

(ii) Parasitic nutrition: This is the type of plant nutrition by which a few plants derive their organic substance from other plants. Such plants are referred to as parasite while the plants from which they derive their nourishment and protection is referred to as host.

Parasites causes harm to their host and can sometimes leads to the death of the host. This is type of relationship in which the parasite gains while its host is at loss.

(iii) Mutualism (symbiosis) — This is a mode of feeding relationship whereby two organisms are living together for the common benefit of each other. The relationship may be between organisms that belong to the same group or different groups.

Example is seen in the relationship between nitrogen fixing bacteria, rhizobium and root noodles of leguminous plants as well as fungi and algae in lichens.

(iv) Epiphytic nutrition — This is the mode of plant of nutrition that occurs when plants attach themselves to other plants for support. They acquire minerals and water from the position of attachment to the host plants but produce their own food through photosynthesis because they have green leaves and chlorophyl.

(b) (I) Light reaction takes place in the grana of the chloroplast which contains chlorophyll, a pigment that traps light energy during the process of photosynthesis. The absorption of light energy by chlorophyll assists in the splitting of water molecule into hydrogen and hydroxyl ions as shown in the equation below:

4H20 ? Light energy ? 4H+ ? OH- - 40H .

The hydroxyl components obtained again react with each other to give rise to water and oxygen as shown in the equation below: 20H + 20H ? 2H20 + O2 . The overall reactions = 4H20 radiant energy 4H+ + 2H20 + O2 + 4e.

In the process of light reaction, electrons are transferred to photosystem I, two molecules of ATP are produced from ADP and inorganic phosphate. ADP + P1 ? ATP (photophosphory — lotion) electrons move further to another photosystem

1. NADP is reduced to NADPH and two molecules of NADPH are synthesized.

(ii) Dark reaction takes place in the stoma of the chloroplast in the presence of NADPH and ATP. The Hydrogen (H) produced in the light reaction passes through series of reactions in which they reduce carbon dioxide to form sugar(glucose) as represented in the following equation: CO2 + 4H ? CH2O + H20. The reactions are catalysed by enzymes.

(c) (i) Explanation of filter feeding in mosquito: The head of a mosquito has brushes, mandible and maxillae. Ventral surface of the head is upward and this allows the pair of brushes at the sides of the Mouth to sweep through water and enmesh small food particles which are combed into the mouth by the maxilla and mandibles.

(ii) Explanation of parasitic feeding in tape worm: The head or (scolex) of a tape worm has hooks, rostellum and suckers. The hooks and the suckers allow them to attach themselves to the walls of the intestine of its host. The whole body surface is adapted for absorption of digested food from its host.

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adhixbelly answered the question on April 10, 2018 at 16:27