Mechanism of Transport Test - 1

• Vitamin A (Retinol) is the fat-soluble vitamin which is essential for vision, growth, differentiation of epithelial tissue. Its deficiency causes Night Blindness, Xerophthalmia, and abnormal epithelial growth.
• Xerophthalmia is abnormal dryness of the conjunctiva and cornea of the eye, with inflammation and ridge formation, typically associated with vitamin A deficiency.
• Vitamin K is fat soluble vitamin which helps in blood clotting, prevention of excessive bleeding. Its deficiency causes faulty blood clotting.
• Vitamin B₁ or thiamine is water soluble vitamin which is essential for repair and growth of tissues. It acts as thiamine pyrophosphate in Krebs cycle. Its deficiency causes Beri-beri.
• Vitamin B₃ or Niacin is water-soluble vitamin and its deficiency causes pellagra.

As per “Active K⁺ transport mechanism” accumulation of K⁺ ions occurs in the guard cell during the day in response to light. It increases the turgidity of guard cells consequently stomata open. During night, ions move out of the guard cells into surrounding epidermal cells consequently guard cell becomes flaccid and stomata close.

Cells of phloem contain large quantities of organic solutes in soluble form.

Munch mass flow: This theory is based on difference in osmotic pressure in leaf mesophyll cells and root cells.

Linsbauer (1916) suggested that the removal of CO₂ by photosynthesis causes opening of stomata by changing the permeability of the guard cells to different kinds of solutes and guard cells are more permeable when the stomata are closed.

K⁺ are balanced by organic anions i.e., malate and some Cl^– ions are also taken in to neutralize a small percentage of K⁺, this mechanism is controlled the turgidity of guard cells.

According to Yin and Tung (1948), enzyme phosphorylase in guard cells is responsible for starch glucose interconversion.

The stomata in succulent plant of CAM plants (like Opunita, Bryophyllum etc.) open during night and remain closed during the day time and found in lower surface. This type of stomatal opening is called scotoactive type.