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Physiological and Morphological Changes in Ipomopsis aggregata Along an Elevational Gradient

Authors: Turner, Z. M.
Year: 2006
Publisher: UNKNOWN
Keywords: IPOMOPSIS AGGREGATA, ELEVATION GRADIENT, ECOPHYSIOLOGY, ENVIRONMENTAL STRESS, PHOTOSYNTHESIS, GLUTATHIONE REDUCTASE, OXIDATIVE STRESS

Abstract

Changes in the morphology and physiology of Ipomopsis aggregata and changes in en- vironment were assessed along a roughly 1000 m elevation gradient at seven sites in the Rocky Mountains of central Colorado. Sites at the ends of the gradient had the lowest soil moisture, the lowest two being in sagebrush scrub land and the highest on rocky alpine talus. Soil moisture decreases for the highest five sites but is intermediate for the lowest two sites. Minimum temperatures and relative humidity decreased with altitude. I. aggregata showed significant changes in leaf structure, glutathione reductase activity and water use efficiency which correlate best with elevation. Plants at higher elevations had larger leaves with higher specific leaf area (SLA) and higher water content. Stomatal density declined at both ends of the gradient. Leaf hair density was very high at the low desert-like site but otherwise increased significantly with elevation. Glutathione reductase (GR) activity was very high at the second lowest site but low at the lowest, even though both sites should experience similar drought stress. GR activity increased significantly for the higher five sites. Photo- synthetic rates were similar between all sites measured but transpiration was significantly lower at the lower and drier site compared to the higher sites. Water use efficiency (WUE) was significantly higher at the lower site compared to the higher sites. Overall, I. aggregata does not appear to be experiencing increasing environmental stress with increasing elevation and in fact seems to thrive at high elevation sites. 1

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