PlantDefenses213-page3

PlantDefenses213-page3 - and their growth patterns, which...

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Plant Stress and Defense Mechanisms - 3 Salts High concentrations of mineral salts in soil affect water potential and decrease water absorption. High concentrations of some mineral salts, such as sodium, are also directly toxic to plants. Some plants can produce organic solutes for distribution in root cells that maintain a more-negative water potential in the root cells to facilitate water movement from soil into the root. This is marginally effective for short term. There are some plants, called halophytes that live in saline soils. Most have active salt glands in leaf epidermal cells that excrete salt. One plant, of very arid regions, called Nolana , has salt glands used to obtain water. Water from the atmosphere condenses on the salt secreted on the surface of the leaves. then actively transports the water into the leaf tissue. Mangrove Salt Excretion Salt Glands General Climate Response The field of dendrochronology, or study of tree rings, examines long-lived tree species
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Unformatted text preview: and their growth patterns, which correlates exceptionally well to general climate and climate change. Rings of both living and dead trees can be examined, using fine cores. For example, a forest of conifers in Mongolia has specimens available from the 1500's through today. Ring pattern indicates a general warming climate, with more growth (wider rings) during the past half century. Moisture has similar effects on tree rings. In the state of Washington, specimens in the coastal rain forest have much wider growth rings than those of the Cascades. Looking more specifically, in Washington, growth rings lag one year behind the climate pattern. The precipitation in 2010 winter (largely snow pack) determines the early xylem growth for the spring of 2011. The reserves the tree was able to accumulate in the spring-summer of 2010, based on that winter's snow pack, provide the reserves for the spring early growth in xylem for 2011....
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