Key message

Restricted access of light for stems reduced carbon acquisition there and limited the biomass growth of the roots.

Abstract

Light access can affect the microatmosphere within stems, creating favourable conditions for photosynthesis. We tested the hypothesis that stem photosynthesis modifies carbon allocation within plants and also can affect root growth. To verify this hypothesis, parts of Clusia minor L. stems were covered with dark material for 8 months to block light access to stems, and then, we compared morphological traits, biomass increment, photosynthetic activity and carbon isotopic signature (δ¹³C) in plants with dark- and light-exposed stems. Clusia minor stems were characterized by chlorophyll presence from pith to cortex, active photosystem II and 79% re-assimilation of respired CO₂. We also revealed 24-h changes in the δ¹³C of carbohydrates exported from leaves. Keeping stems in darkness led to a significant lowering in root biomass and shoot-to-root weight index (I_w). Moreover, reductions in stem CO₂ efflux and the δ¹³C in the roots and stems were also observed. Our results indicate that the lack of stem photosynthesis affects photosynthate flux to heterotrophic organs, such as roots, stems and probably expanding leaves.

中文翻译：

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茎光合作用在小clusia小植物碳分配中的重要性

关键信息

茎干的光受限，减少了那里的碳吸收并限制了根的生物量生长。

抽象

光线的进入会影响茎中的微气氛，从而为光合作用创造有利条件。我们测试了以下假设：茎的光合作用修饰了植物内的碳分配，也可能影响根系生长。为了验证这一假说，部分Clusia轻微大号。茎覆盖着暗色材料8个月以阻挡光进入茎，然后，我们比较形态性状，生物量增量，光合活性和碳同位素特征（δ ¹³ C）在植物中有黑暗和光照暴露茎。小clusia茎的特征是从叶髓到皮层存在叶绿素，活性光系统II和呼吸CO _2的79％重新同化。我们还透露，在δ24小时变化¹³从叶片出口碳水化合物的温度。将茎保持在黑暗中会导致根生物量和枝根重量指数（I _w）大大降低。此外，在削减CO茎₂流出和δ ¹³下，在根和茎中也观察到。我们的结果表明，缺乏茎的光合作用会影响光合产物通向异养器官，例如根，茎和可能扩张的叶片。