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Abstract Detail

Physiological Section

Carvalho, Monica R. [1], Woll, Arthur [2], Niklas, Karl [1].

Calcium and zinc accumulation through leaf ontogeny.

Studies on the distribution and differential accumulation of elements in plant tissues have traditionally focused on heavy metals in regard to plant tolerance to extreme concentrations or bioremediation incentives. Detection systems such as x-ray fluorescence spectroscopy are faster and provide higher resolution for imaging and quantifying light elements in biological samples (e.g., Ca, Zn, and K). Here, we examine the spatiotemporal distribution and accumulation of Ca, Zn, and K throughout leaf growth and maturation. Eight developing leaves of Populus tremuloides x alba ranging across leaf plastochrons 1 through 10 were selected to ensure observation of the sugar sink-to-source transition. This transition requires coordinated changes of multiple core metabolic processes, and is thus expected to involve alterations in essential and non-essential element distributions as tissues mature and effect a reversal in phloem flow direction. Leaves were dried and scanned using elemental x-ray spectroscopy at the Cornell High Energy Synchrotron Source (CHESS). Additional cross-sections of fresh leaves were scanned to check for tissue-specificity in the accumulation of targeted elements. Elemental maps for each leaf were produced using dynamic analysis as implemented in GeoPixe. We focused on the distribution and accumulation of calcium because it shows tissue specificity that varies across leaf developmental stage. Calcium is mainly concentrated in major veins in early developmental stages and increases its concentration in the leaf mesophyll in older plastochrons. This accumulation is not uniform across the leaf lamina, but occurs basipetally. This spatiotemporal pattern matches the sequence of photosynthetic maturation, positive carbon balance, and sugar export. Since Ca is only transported through the xylem, its accumulation in tissues is likely to reflect the maturation of xylem in minor veins and the enhancement of the transpiration stream. Our results independently confirm that xylem and phloem maturation is spatially and temporally coordinated with the onset of sugar export in leaves.

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1 - Cornell University, Department of Plant Biology, Ithaca, NY, 14853, USA
2 - Cornell University, Cornell High Energy Synchrotron Source, Ithaca, NY, 14853, USA

leaf growth
x-ray spectroscopy
leaf veins.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PPS008
Abstract ID:1197
Candidate for Awards:None

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