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Nary a drop to drink Each fall as we anticipate the winter rains (Claire writes from a Californian perspective but it’s also true in the other parts of the world), I marvel at the ability of our native plants to survive half a year or more without a drink of water. How do they do it? Different plants have different kinds of adaptations to water deficits. Three common adaptations are high root-shoot ratios, water saving, and tolerance of drought. Some plants effectively increase their water uptake by growing a lot of roots, resulting in a high "root-shoot ratio." That means that the plant has put relatively more energy into growing underground (where the water is) than above ground. Some species actually send out exploratory roots in search of new water sources during drought. Plants like the cactus avoid water stress by saving their own water. Their roots can tend to be very shallow, enabling the plant to take up water following even a light rainfall. Some conifers are also considered water savers, primarily due to their aspects of their physiology that results in very low transpiration rates (the loss of water from plant cells to the atmosphere). "Drought tolerance" is varied and complicated. Suffice it to say that some species can tolerate drying out and starvation (lack of carbon dioxide) better than others, whether due to an ability to lower metabolism or complex physiological adaptations. Many mosses and lichens, for example, can dry out and then resume growth once they are rehydrated. Interestingly, there can be a "hardening process" in which dry conditions that stress a plant without killing it help that plant develop characteristics that enable it to improve its drought tolerance. We know how thirsty we get after half a day with no water. That some plants can survive for half a year or more with nary a drop to drink is truly one of the marvels of the natural world. |
Interesting little tidbits come from Clare Nunamaker. She is a registered forester and member of NorCal SAF and the Forest Guild. from the National Science Foundation |
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web master: Jake the computer
guy at JMForestry. |
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