Species-specific bindin receptors present on the egg vitelline envelope.

TLS Online TPP Program

#Id: 7530

#Unit 6. System Physiology – Plant

Phototropism Is Mediated by the Lateral Redistribution of Auxin

In response to a directional light stimulus, the auxin produced at the tip, instead of being transported basipetally, is transported laterally toward the shaded side. Two flavoproteins, phototropins 1 and 2, are the photoreceptors for the blue-light signaling pathway that induces phototropic bending in Arabidopsis

TLS Online TPP Program

#Id: 7531

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7532

#Unit 6. System Physiology – Plant

According to the current hypothesis, the gradient in phototropin phosphorylation induces the movement of auxin to the shaded side of the coleoptile. Once the auxin reaches the shaded side of the tip, it is transported basipetally to the elongation zone, where it stimulates cell elongation. The acceleration of growth on the shaded side and the slowing of growth on the illuminated side (differential growth) give rise to the curvature toward light.

TLS Online TPP Program

#Id: 7533

#Unit 6. System Physiology – Plant

Dense plastids serve as gravity sensors

Gravity does not form gradient.

The only way of sensing gravity is through the motion of a sedimenting body.

In plants intracellular gravity sensors are large, dense amyloplast.

Statoliths –amyloplasts that function as gravity sensors.

Statocytes-specialized gravity sensing cells in which statoliths are present.

TLS Online TPP Program

#Id: 7534

#Unit 6. System Physiology – Plant

Strigolactones as signal that interact with auxin in regulating apical dominance Strigolactone is a group of trepenoids that produced in both shoots and roots and is transported through xylem

TLS Online TPP Program

#Id: 7535

#Unit 6. System Physiology – Plant

GA levels in plants are correlated with stem length, internode elongation and seed germination. Play role in seed germination, transition to flowering, and pollen development.