HORT 476 Exam 2: L9

Photoperiodism

Photoperiod triggers flowering and development

Phototropism

Response to the direction of the light

Photomorphogenesis

Spectral quality, or ratio or red/far-red is important for morphogenesis.

Low light

stress on plants, as it limits net carbon gain and plant growth.

High light

can damage photosynthetic apparatus, particularly under non-optimal conditions

Dynamic response

result of perturbations of steady state conditions; sudden changes in light (ie - sunflecks)

Steady-state response

constant response achieved after exposure of a leaf to a constant irradiance for some period of time until steady-state is reached

shade plant

can refer to a genotype which is "adapted" for shade OR to a genotype which is "acclimated".

Sun plant

can refer to plant grown in high light conditions or to a shade avoiding species

Light attenuation depends on

1. amount of leaf area
2. arrangement of leaves

extinction coefficient is __________ for vertically inclined leaves such as grass.

Lower

extinction coefficient is higher for ___________ leaves

Horizontal

extinction coefficient approaches _____ for perfectly horizontal leaves

1

Why would leaves be more vertically inclined in high light environments?

minimizes photoinhibition and increases penetration of light to lower leaves, maximizing whole-canopy photosynthesis