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Xylem conductivity of petioles and primary stem tissues at stem terminals of herbaceous plant species

Evans, Lance S., Wiley, Walter, Auricchio, Christopher
The journal of the Torrey Botanical Society 2016 v.143 no.3 pp. 311-321
apical meristems, cell proliferation, diameter, equations, flowers, herbaceous plants, leaf area, petioles, shoot meristems, stems, xylem
Shoot apical meristems produce stem tissues, produce leaves, and produce flowers. Cell proliferation characteristics of meristems are dependent upon cell maturation processes and the functions of newly formed cells. Cells of stem terminals depend upon water availability from other plant portions. Inadequate moisture availability to stem terminals reduces shoot growth rates and leaf production rates. Xylem conductivity measurements of terminal shoot meristems and small leaves were approximated using the Hagen-Poiseuille equation to determine relationships between xylem contributions to leaves versus xylem conductivity within stems. Analyses of petiole and stem xylem conductivities for the 23 herbaceous plant species were confined to stem terminals that only had primary xylem cells in stems and only five leaves or leaf pairs. Among stem segments (10 mm to 64 mm in length) among species, the largest leaf areas ranged from 2.34 cm² to 54 cm², stem diameters ranged from 0.82 mm to 3.83 mm, and maximum leaf petiole and stem xylem conductivities were 0.12 g cm MPa⁻¹ s⁻¹ and 0.35 g cm MPa⁻¹ s⁻¹, respectively. For pooled samples, petiole xylem conductivity was well scaled with leaf area of largest leaves (r² = 0.76). For pooled samples, stem conductivity was well scaled with cumulative petiole conductivities (r² = 0.94). When the largest diameter stem sections from each species were considered, stem xylem conductivity was well scaled with mean radius of conduits (r² = 0.82). Overall, stem xylem conductivities were strongly linked to petiole conductivities as leaves developed. Petiole xylem conductivity was well scaled with stem conductivities for all 23 species with markedly different leaf areas.