Mechanism Of Stomatal Movement

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MECHANISM OF STOMATAL MOVEMENTS

 

1) STARCH- SUGAR HYPOTHESIS:

It is proposed by sayer in 1923

IN LIGHT:

IN DARK:

Photosynthesis occurs

Respiration occurs

pH increases↑

pH decreases ↓

Carbon dioxide Co₂↓

Carbon dioxide Co₂ ↑

Enzyme: phosphorylase is used

Enzyme: phosphorylase is used

Sugar increases ↑ so endosmosis take place

Starch increases ↑ so exosmosis take place

Turgor pressure increases ↑

Turgor pressure decreases ↓

Diffusion pressure deficit (DPD) increases ↑

Diffusion pressure deficit (DPD) decreases ↓

Stomata = opens

Stomata = closes

Starch is converted in to glucose -1- phosphate

glucose -1- phosphate is converted in to Starch

 

 

 


2) STEWARD HYPOTHESIS:

It is proposed by steward in 1964

IN LIGHT:

IN DARK:

Photosynthesis occurs

Respiration occurs

pH increases↑

pH decreases ↓

Carbon dioxide Co₂↓

Carbon dioxide Co₂ ↑

Enzyme: phosphorylase is used

Enzyme: Heterokinase is used

Turgor pressure increases ↑

Turgor pressure decreases ↓

Diffusion pressure deficit (DPD) increases ↑

Diffusion pressure deficit (DPD) decreases ↓

Stomata = opens

Stomata = closes

Starch is converted in to glucose + phosphate

glucose - 6 - phosphate is converted in to Starch

 

 

 


3) THEORY OF K^ + TRANSPORT:

It is proposed by Levit in 1974

IN LIGHT:

IN DARK:

K^+ started entering into guard cell

K^+ stops entering into guard cell

pH increases↑

pH decreases ↓

Guard cell becomes turgid

Guard cell becomes flaccid

Turgor pressure increases ↑

Turgor pressure decreases ↓

Diffusion pressure deficit (DPD) increases ↑

Diffusion pressure deficit (DPD) decreases ↓

  1. Increases in accessory cells↑
  2. Decreases in guard cells↓

Stomata = opens

Stomata = closes

Starch is converted in to potassium malate

potassium malate is converted in to malic acid


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