Transpiration, Respiration and Water Uptake

Floral Careers Plant Propagation

Transpiration Defined

• The loss of water vapor through open leaf stomata.

Transpiration

• How does transpiration work?• On sunny, warm days the sun warms up the leaf

surfaces.• The water in the cells of a leaf begins to

evaporate.

Transpiration

• Water vapor collects in the spongy mesophyll tissue of the leaf.

• The water vapor moves out of spongy mesophyll, through the open stomata, and into the drier air surrounding the leaf.

• As water evaporates from the spongy mesophyll, new water molecules are delivered to the leaf through the xylem in leaf veins.

Rate of Transpiration

• The rate of transpiration is affected by the following 3 things:

• Humidity; during dry, less humid days the rate of transpiration increases.

• Temperature; the rate of transpiration is greater on hot days than on cooler, cloudy days.

• Wind; the rate of transpiration is greater on windy days than calmer days.

Water Movement

• There are 3 main factors that affect the movement of water through plants. They are:

• Osmosis• Transpiration• The properties of water molecules

Root Hairs Osmosis

• Water enters root hairs by osmosis.

• Water quickly moves through the root hairs and into the xylem.

• Transpiration “pulls” or “sucks” water up stems in much the same way that you pull liquid up through a straw.

• Water molecules (H2O) are electrically charged.

• Because of this water molecules stick to one another like little magnets.

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Respiration

• Compliments photosynthesis.

• Inputs:– sugar– oxygen

• Outputs:– water– carbon dioxide– heat– chemical energy (used in plant growth)

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