Mechanism Of Stomatal Movement

 

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 ↓ Increases in accessory cells↑ Decreases in guard cells↓
Stomata = opens	Stomata = closes
Starch is converted in to potassium malate	potassium malate is converted in to malic acid