Nutrition in Plants

Life is identified via the

• ability carry out the life processes

• exhibiton of growth and response to stimuli

Processes like Respiration, Reproduction, Excertion, Nutrition, Control and Coordination, transportation, which are vital for sustenance of life are called life processes

• Life processes are susatined through the series of anabolic and catabolic reactions happening within our body i.e, metabolism

Nutrition refers to the process via which carbon based raw materials (food) present in the enviroment are acted upon either via anabolic or catabolic pathways to produce an absorbable form through which energy and nutrients (components of food reuqired for growth and maintanence) are derived/the proces via which living organisms ingest food to obtain energy snd nutrients from it.

Why nutrition?

→ Organisms need food to obtain nutrients (for growth and maintenance) and energy (for carrying out life processes). Yet, as the enviornment is not under control of an individual it is often that organisms aren’t able to obtain energy from the source as it is, hence it needs to be broken down

Nutrition varies in organsims

• based on no.of cells ;

  • In unicellular organisms diffusion is the primary mode of obtaining raw materials while in case of multicellular organisms specialised organs perform the function

• based on complexity of carbon;

  • use of simple (inroganic) carbon molecules as raw materials or complex (organic) carbon molecules

Autotrophic mode of nutrition:

• The mode of nutrition via which organisms such as green plants synthesise their own (organic) food using inorganic raw materials.

• It’s an anabolic process that can be carried out in two ways;

  • Photosynthesis :: anabolic process through which cholorphyll containing, autotrophic organisms such as green plants, euglena or cyanobacteria synthesise food with sunlight as the source of energy (which is converted into chemical energy). It is heavily dependant on redox reactions (reduction-oxidation) and occurs within the chloroplasts present in mesophyll of leaves (in plants)

  • Chemosynthesis :: anabolic process through which autotrophic organisms such as chemosynthetic bacteria synthesise food in presence of chemical energy

Mechanism of photsynthesis

• Light Phase;

  • Occurs in the thylakoid in presence of sunlight. Steps involved;

    • Absorbtion of light energy; Chlorphyll absorbs sunlight, gets excited to release electrons

    • The released electron(s) combine(s) prexisting ADPs and inorganic phosphate to form ATP moleclues

    • Photolysis of water occurs simaltaneously. Oxygen is directly released into the atmosphere while Hydrogen ions cause pre-exisiting NADP molecules to reduce into NADPH molecules

• Dark Phase;

  • Occurs in stoma in absence of sunlight

  • ATP and NADP formed in first step reduce CO2 to form carbohydartes (glucose)

  • The carbohydrates are stored in form of a polymer of glucose; starch

• Raw materials required;

  • Water

  • Co2 → taken in through stomata

  • Sunlight

  • Minerals

  • Chlorophyll

• Exception: Desert Plants (xerophytes)

  • Can’t keep pores open during day time (transpiration → excess water loss)

  • Thus, gaseous exchange happens at night time and

  • the carbon dioxide that’s taken in is stored in form of an intermideate molecule (b/w CO2 and H2O)

  • Sunlight acts upon the molecule during day