Abstract
Calcium (Ca) is an essential macronutrient in plants and is an important component of many cellular structures and physiological processes as well as overall forest function. Aluminum (Al) in soil solution can inhibit Ca uptake by plants and disrupt many Ca-dependent metabolic and physiological processes of plants. The ratio of Ca to Al in soil solution can be an important indicator of forest health, especially on acid soils. We used sequential chemical extractions (water, acetic acid and hydrochloric acid) to assess the chemical availability of Ca and Al in foliage from mature red spruce (Picea rubens Sarg.) trees growing under ambient environmental conditions. In plants deficient in Ca and with intermediate total foliar Ca concentration ([Ca]), Ca preferentially accrued in labile and physiologically available forms (water- and acetic acid-extractable). In plants with total foliar [Ca] above a "sufficiency" threshold, Ca also accrued in a chemically sequestered form with low solubility (HCl-extractable), suggesting that Ca sequestration is an inducible process in response to excess foliar Ca. Because it has low solubility, it is likely that sequestered Ca is unavailable for Ca-dependent physiological processes. Immobilization of Al in foliage was related to Ca sequestration, suggesting that Ca sequestration may provide a passive mechanism for Al tolerance in the foliage of these trees. Aluminum immobilization was evident based on the ratio of HCl-extractable Al to the more labile (water- and acetic acid-extractable) forms of Al. Sufficient labile Ca combined with Al sequestration was associated with plant health, including enhanced foliar accretion of Mg and Mn, greater tree growth, enhanced foliar cold hardiness and reduced winter injury. These findings demonstrate that not all chemical forms of foliar Ca and Al are of equal physiological significance and underscore the importance of assessing the biologically significant element forms in biogeochemical research.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
