apical Cytokinin mitosis leaf node Auxin cell elongation

gibberellin elongation of internodal regions

Apical meristem Zone of elongation Leaf node Internodal region Tip of root or shoot where cell division occurs cytokinin Zone of elongation Area behind the apical meristem where cells enlarge auxin Leaf node Area on stem from which a lateral leaf grows Internodal region Length affected by gibberellin node Internodal region Area of the stem between leaf nodes gibberellin

promotes cell division at the meristems cytokinins

causes cells elongation AUXIN Small new cell from mitosis Large elongated cell causes cells elongation in zone of elongation auxin

stem elongation gibberellin

Summary table page 39 CCEA A2 text QUESTION 3 PAGE 45

Light is perceived by the tip of the coleoptile. darwin The coleoptile is positively phototropic. It bends towards the light by unequal elongation of the region just behind the tip. Light is perceived by the tip of the coleoptile.

boysen - jensen Mica prevents movement of auxin from the tip to the shaded side of the coleoptile.

Auxin diffused into the agar block. went Auxin diffused into the agar block. Auxin from the block diffused down one side of the shoot, causing cells to elongate and the shoot to bend. Auxin is produced in the tip but the cells behind the tip respond to its affect. Tip on gelatine block exposed to light. Tip replaced by off centre block and placed in dark. Shoot grew bent

PHYTOCHROME: controls flowering RED light in daylight P660 P730 FAR RED light Slow conversion in dark

short day plants

long day plants