PARENT SESSION
Oral Session # 61: Biogeochemistry IV: Al, Ca, P, and DOC.
Presiding: R Fitzhugh
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 205.
Differential biochemical partitioning and physiological availability of calcium and aluminum in red spruce foliage.
Borer, Catherine*,1, Schaberg, Paul2, DeHayes, Donald1, Hawley, Gary1, 1 The University of Vermont, Burlington, VT2 USDA Forest Service, South Burlington, VT
ABSTRACT- Calcium (Ca) is an essential macronutrient in plants, and is an important component of many cellular structures and physiological processes. Aluminum (Al) can obstruct Ca uptake, and may compete for biochemical Ca binding sites, thus inhibiting many Ca-dependent processes. Ca to Al ratios in the soil have been described as important indicators of both site-specific forest health and plant damage that can result from soil acidification. By means of sequential extractions of foliage from mature red spruce (Picea rubens Sarg.) trees growing under ambient environmental conditions, we found that Ca preferentially accrues to labile and physiologically active forms at low total foliar Ca concentrations. At higher levels of total Ca, substantial quantities of low-solubility Ca also accumulate in the foliage. This inducible chemical sequestration of Ca occurs only within the documented foliar Ca sufficiency range. A similar pattern of differential chemical sequestration was found for Al. Our results suggest that foliar Al sequestration may provide for passive Al tolerance as a "side-effect" of Ca partitioning. Accretion of sufficient physiologically available foliar Ca, in conjunction with Al sequestration, was associated with greater tree growth, elevated accretion of other nutrients, enhanced cold hardiness, and reduced winter injury. In contrast, total foliar Ca and Al content, as well as foliar Ca to Al ratios were not closely related to cold hardiness or winter injury. These data demonstrate that not all chemical forms of foliar Ca and Al are equally physiologically relevant, and underscore the importance of assessing relevant components in biogeochemical research studies.
Key words: aluminum, Picea rubens, calcium, plant health