photoperiod

pho.to.pe.ri.od

n.（名词）
The duration of an organism`s daily exposure to light, considered especially with regard to the effect of the exposure on growth and development.
光周期：有机物每天暴露于阳光的时间，着重考虑的是暴露于阳光对生长和发展的影响

【引伸】
pho.tope.riod.ic