首页>
美国卫生研究院文献>Annals of Botany
>The Role of the Storage Carbon of Cotyledons in the Establishment of Seedlings of Hymenaea courbaril Under Different Light Conditions
【2h】
The Role of the Storage Carbon of Cotyledons in the Establishment of Seedlings of Hymenaea courbaril Under Different Light Conditions
• Background and Aims Hymenaea courbaril (Leguminosae-Caesalpinioideae) is a tree species with wide distribution through all of the Neotropics. It has large seeds (approx. 5 g) with non-photosynthetic storage cotyledons rich (40 %) in a cell wall polysaccharide (xyloglucan) as a carbon reserve. Because it is found in the understorey of tropical forests, it has been considered as a shade-tolerant, late-secondary species. However, the physiological mechanisms involved in seedling establishment, especially regarding the interplay between storage and light intensity, are not understood. In this work, the ecophysiological role of this carbon cotyledon reserve (xyloglucan) is characterized, emphasizing its effects on seedling growth and development during the transition from heterotrophy to autotrophy under different light conditions.• Methods Seedlings of H. courbaril were grown in environments with different light intensities, and with or without cotyledons detached before xyloglucan mobilization. Development, growth, photosynthesis and carbon partitioning (dry mass and [14C]sucrose) were analysed in each treatment.• Key Results The detachment of cotyledons was not important for seedling survival, but resulted in a strong restriction (50 % less) of shoot growth, which was the main sink for the cotyledon carbon reserves. Carbon restriction promoted an early maturation of the photosynthetic apparatus without changes in the net CO2 fixation per unit area. The reduced surface area of the first leaves in seedlings without cotyledons was evidence of limited growth and development of seedlings in low light conditions (22 µmol m−2 s−1 photon flux).• Conclusions There is an increase in the importance of storage xyloglucan in cotyledons for H. courbaril seedling development as light intensity decreases, confirming that this polymer plays a key role in the adaptation of this species to establish successfully in the shadowed understorey of the forest.
展开▼
机译:•背景和目的Hymenaea courbaril(Leguminosae-Caesalpinioideaeae)是一种树木,在所有新热带地区都有广泛分布。它具有大的种子(约5 g),在细胞壁多糖(木葡聚糖)中有非光合作用的子叶富含(40%)作为碳储备。由于它是在热带森林的底层中发现的,因此被认为是耐荫的次生树种。然而,还不清楚幼苗建立中涉及的生理机制,特别是关于贮藏和光强度之间的相互作用。在这项工作中,表征了该碳子叶储备(木葡聚糖)的生态生理作用,强调了它在不同光照条件下从异养向自养转化过程中对幼苗生长和发育的影响。•方法在动员木葡聚糖之前,有不同的光强度,以及是否分离了子叶。分析了每种处理方法的发育,生长,光合作用和碳分配(干重和[ 14 sup> C]蔗糖)。•关键结果子叶的分离对幼苗的存活并不重要,但其子叶的脱落对幼苗的存活并不重要。限制(少50%)的芽生长,这是子叶碳储量的主要来源。碳限制促进了光合装置的早期成熟,而每单位面积的净CO2固定不变。没有子叶的幼苗中第一片叶子的表面积减少,表明在弱光条件下(22 µmol m −2 sup> s -1 sup>光子通量),幼苗的生长和发育受到限制。 )。结论随着光强度的降低,贮藏木葡聚糖对于H. courbaril幼苗生长的子叶的重要性越来越高,这证实了该聚合物在该物种的适应过程中起着关键作用,从而成功地建立了该树种的阴影下层。森林。
展开▼