Principles & practices of seed production ( Photoperiod and Temperature Requirements )

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 Photoperiod and Temperature Requirements 

Flowering is a prerequisite for seed production. 

Internal & external signals affecting the flower production

 Plant age or size and more specifically endogenous level of certain hormones are considered as internal cues; while, length of day/night and low temperature are external signals

 usually 0-5°c is required for vernalization

 seeds of some crops if exposed to low temperature during imbibition can be vernalized e.g

lettuce, turnip, spinach, chinese cabbage, red beet, white mustard

Vernalization temperature          Developmental stages                                                                                                      No of leaves
Crops	Cauliflower& Brocoli	20°c-30°c		carrot	8-12
	Onion	2°c-3°c		onion	4-7
	Tropical onion	9°c-13°c		cauliflower	4-12
				cabbage	4-15
				coreopsis	8
				gailardia	16
				rudbeckia	10
				tobacco	37

Continuous rainfall during flowering can wash out stigmatic fluid and suppress anther dehiscence