Differences between root and stem wood in seedlings and sprouts of Sessea brasiliensis (Solanaceae)

Abstract Young Sessea brasiliensis trees derived from seeds and sprouts after coppicing were analyzed for differences in axial variation of anatomical features. It was hypothesized that 1) quantitative variation in anatomical features in the axial direction would indicate adjustments in water conductivity and mechanical strength along tree height and 2) significant quantitative differences in anatomical features would be observed between trees originating from seed compared to those derived from sprouts after coppicing. Results showed that wood originating from sprouts after coppicing developed differently from wood originating from seeds. Specifically, for seed provenance samples, narrower vessels were observed in the transition zone, whereas for sprouting provenance, narrower vessels were seen in roots and trunk base. Also, when comparing axial variation between seeds and sprouts, vessel diameter was smaller in plants of seed origin in the transition zone, whereas fiber diameter was smaller in trunk top and branch in plants of seed and sprouting provenances, respectively. Higher rays were observed in branch and trunk top when comparing different axial position in both origins. Thus, the first hypothesis is confirmed by significant axial variation in vessels, fibers and rays, and the second hypothesis is confirmed by the significant differences observed between trees of seed and sprout origins.

摘要
本研究针对实生起源与经平茬（coppicing）后萌发的萌条起源的巴西塞西亚木（Sessea brasiliensis）幼树，开展解剖特征轴向变异差异分析。本研究提出两项假设：其一，解剖特征的轴向数量变异可反映树木沿树高梯度的水分传导能力与机械强度的适应性调控；其二，实生起源与萌条起源的林木，其解剖特征存在显著的数量差异。
研究结果显示，萌条起源植株的木材发育模式与实生苗存在显著差异。具体而言，实生种源样本的过渡区导管直径更窄，而萌条种源样本的导管窄化现象则出现在根系与树干基部。此外，对比两类起源林木的轴向变异模式可见：实生起源植株过渡区的导管直径更小，而实生起源植株的树干顶部、萌条起源植株的枝条纤维直径则分别更小。对比两类起源的不同轴向位置，枝条与树干顶部的木射线高度更高。
综上，导管、纤维与木射线均存在显著轴向变异，证实了第一项假设；而实生起源与萌条起源林木间的解剖特征差异显著，验证了第二项假设。