Osmotic characteristics of water retention structures of Bursera microphylla in relation to soil salinity

(1) Red Bluff High School, Red Bluff, California

Cover photo for Osmotic characteristics of water retention structures of <i>Bursera microphylla</i> in relation to soil salinity
Image credit: Lisa Fotios

With a worldwide increase in soil salinity, as well as the climate crisis raising global temperatures, it is important to understand the effects of soil salinity on plant survival. One way to understand how plants may evolve to survive in these xeric desert environments is to gain a further understanding of existing halophytic (live in saline environments) and/or xerophytic (live in dry, arid environments) plants. Bursera microphylla in particular is quite interesting because it is both a halophyte and a xerophyte. One reason it is able to survive in dry environments is due to its bulbs at the base of the trunk and major limbs of the tree, which have been shown to store water during droughts. To facilitate mineral uptake, plants use ATP to transport NaCl ions into the plant, which facilitates water uptake. Because observed field conditions in the Baja California Peninsula were extremely xeric, most plants there have distinct evolutionary traits to facilitate water storage or retention. The Elephant Tree (Bursera microphylla) gets its name from the abnormal proportions of the base of its stem, which is much wider than much of the tree, and studies show that this disproportionately wide stem can store water for use during times of drought, which are common in the Baja California Peninsula. Our hypothesis was that sodium chloride was taken up through the plant’s root structure to facilitate this water transportation, and that this sodium chloride accumulation was directly proportional to the soil salinity. We tested this hypothesis via light microscopy of plant tissues to observe cell tonicity under different concentrations of saline solution. soil salinity was measured using saturated extraction. The results of this experiment show that most cells within the “bulb” structures were isotonic at a concentration approximately twice as high as that of root tissue and ambient soil salinity, therefore supporting the presented hypothesis.

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