February 7 2013 Focus Question: How does a plant maintain homeostasis?

Plant Homeostasis

Homeostasis: balance of a system Turgid: full of water (crisp) Flaccid: not full of water Wilt: plants wilt when they are not full of water

Transpiration: loss of water by a plant Water is taken up through the roots and leaves via the stoma on the leaves

Stoma (stomata) are the pores on the underside of the leaf Opening and closing of the stoma are regulated by the guard cells

When the guard cells are turgid they pull apart from each other, opening the stoma and allowing gas and water to leave

When the guard cells are flaccid they seal the stoma shut, preventing water loss

When the stoma are open the plant can undergo photosynthesis When the stoma are closed, no photosynthesis can take place because no gas exchange

When stoma are open… Gas exchange Photosynthesis Water loss

When stomata are closed… No glucose production No gas exchange No water loss

Virtual Lab http://www.mhhe.com/biosci/genbio/virtual_labs/BL_10/BL_10.html

Factors that affect transpiration rate Light In bright light transpiration The stomata open wider to allow for gas exchange during photosynthesis Increases

Factors that affect transpiration rate Temperature Transpiration is faster at high temperatures OR Transpiration is slower at low temperatures Evaporation and diffusion are faster at higher temperatures

Factors that affect transpiration rate Wind Transpiration is faster in windy conditions Water vapor is removed quickly by air movement, speeding up diffusion of more water vapor

Factors that affect transpiration rate Humidity Transpiration is slower in humid conditions Diffusion of water out of leaf slows down if leaf is already surrounded by water vapor