Ecology: Lecture 3Ecology: Lecture 3

Plant adaptations to the light environment (Physiological Ecology)

PAR: Photosynthetically PAR: Photosynthetically active radiation (400-740 active radiation (400-740

nm)nm)

P-I CurveP-I Curve

PhotoinhibitionPhotoinhibition

Photosynthesis: reviewPhotosynthesis: review

Photosynthesis: Photosynthesis: light-dependent light-dependent

reactionsreactions What do these

reactions accomplish?

Photosynthesis: Photosynthesis: light-light-inindependent dependent

reactionsreactions What do

these reaction accomplish?

Role of rubisco?

Benefit vs. cost of Benefit vs. cost of rubisco reductionrubisco reduction

Changes in leaf orientationChanges in leaf orientation

Shade-tolerant vs. intolerant Shade-tolerant vs. intolerant plantsplants

Terrestrial Aquatic

Responses to UV Responses to UV radiationradiation

What is the relationship between the ozone layer and UV-B?

What are the consequences of UV-B exposure to primary producers? DNA damage, change in growth form,

reduction in yield Example: In situ studies in the Antarctic ozone

hole (1990) suggest a reduction of 6-12% of primary production due to the ozone hole

Plant defenses against Plant defenses against UV-BUV-B

Compounds that absorb UV-B Effects on photosynthesis? Tropical and alpine plants are more

capable of blocking UV-B radiation Does this make adaptive sense? How so?

Plants with short-lived seasonal leaves were less effective at blocking UV-B rays. Does this make adaptive sense? How so?