Irises and other ____ plants flower only when the hours of darkness fall below a critical value,typically in summer.
A) short-day
B) long-day
C) annual
D) biennial
E) perennial

Question

Irises and other ____ plants flower only when the hours of darkness fall below a critical value,typically in summer.  
A) short-day
B) long-day
C) annual
D) biennial
E) perennial

Quizplus · Accepted Answer

Long-day plants, such as irises, flower when the nights are short and the days are long, typically during the summer months. This is because their flowering is triggered by a decrease in the duration of darkness to below a critical threshold.

Irises and Other ____ Plants Flower Only When the Hours