BIOL 1902 Lecture Notes - Lecture 11: Chlorophyll, Stoma, Filter Feeder
22 Feb 2017
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A two-staged period: the first stage is triggered by a change in the photoperiod. Pytochromes are light-sensitive photopigments: second stage is triggered by colder temperatures (0-10 c). Some trees are cold hardy to -80 c! Ice forms in between the cells (not inside them) Keeping needles (and leaves) on trees creates new problems: solution: xanthophyll pigments. Protects the internal integrity of the cells. Skunk cabbage produ(cid:272)es its o(cid:449)(cid:374) heat (cid:894)as if it"s its o(cid:449)(cid:374) thermostat) Next problem: desiccation (drying up: worse on a sunny, calm day during the winter, conifers retain their leaves so size and shape is very important. Thicker cuticles (waxy covering: hairy underside of leaves. Heath plants have hairy undersides to their leaves. It helps them trap moisture, and to improve circulation: ferns curl up to reduce surface area, deciduous trees have large leaves with a large surface area. They drop their leaves to prevent them from freezing.
