Master Gardener notes: the process of leaf transpiration, leaf respiration, and stomata

My master gardener class has started! As promised, I am going to be talking about what I am learning with an emphasis on our vegetable and fruit gardens. The first piece of information that I would like to share with you is the process of leaf transpiration, respiration, and stomata. Understanding these terms is key to understanding how a plant loses water and what you can do as a gardener to prevent it.

In order to understand respiration and transpiration, we need to first define stomata. Stomata are essentially pores on plant leaves. Through these pores, oxygen and carbon dioxide enter, and, after photosynthesis takes place, water and oxygen exit. Check out this video of stomata.

Leaf respiration is simply plant breathing. It is a very similar process to the breathing that you do in your own body. Through the stoma, carbon dioxide and oxygen enter, and water and oxygen exit. Carbon dioxide is necessary for this process. It is important for us gardeners to note that if there is not carbon dioxide available to the plants (such as in tightly closed greenhouses or cloches) photosynthesis cannot take place and our plants will not grow.

Leaf transpiration is the process by which water is given off from the leaves. Check out this video:

I find this phenomenon highly interesting, because I had briefly read about this process in Steve Solomon’s online book: Water Wise Vegetables. I didn’t completely understand what he meant until now. In this book, Solomon argues that much more water is lost through leaf transpiration than is lost through evaporation in the soil. He contends that increased plant spacing, is far more useful to conserving moisture than use of a mulch (I’ll talk more about the pros and cons of mulches later). You can find Water Wise Vegetables online on the Soil and Health library (I’m having trouble find it, I will contact Solomon for a directly link for you) and you can also purchase out of print copies through Amazon (a link is located on the right sidebar).

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