Abstract:
The photosynthetic differences between adult and juvenile Mediterranean plants were previously studied under field conditions, yet the corresponding differentiation of their photoprotective efficiency has not been sufficiently investigated. The present study aims to examine possible differences in the photoprotective potential between adults and juveniles of two native Mediterranean plants with distinct growth forms. Thus, the seasonal variations in individual carotenoids, electron transport rate (ETR), and non-photochemical quenching (NPQ) were monitored in fully exposed mature leaves from adults and juveniles of the winter deciduous tree Cercis siliquastrum L. and the evergreen sclerophyllous shrub Nerium oleander L. All plants were grown under apparently similar field conditions. In both species, juveniles displayed substantially lower ETR and increased NPQ values than adults in spring, with the differences intensifying during summer drought and diminishing in autumn. Concomitantly, juveniles showed significantly higher chlorophyll-based total carotenoids in spring and summer mainly due to the higher investment in xanthophyll cycle components (VAZ), in combination with an increased mid-day de-epoxidation state (DEPS) and partial retention of zeaxanthin in the dark. In N. oleander, although ETR was lower in juveniles during winter, NPQ was extremely low in both ages. In conclusion, juveniles exhibit enhanced photoprotection potential, especially in the summer, due to their reduced photochemical capacity. The photosynthetic superiority of adults during the favorable spring period may be attributed to the needs of the co-existing reproductive effort.
摘要:
先前在田间条件下研究了成年和幼年地中海植物之间的光合差异,然而,它们的光保护效率的相应差异尚未得到充分研究。本研究旨在研究两种生长形式不同的地中海本地植物的成虫和幼虫之间的光保护潜力可能存在的差异。因此,个体类胡萝卜素的季节性变化,电子传输速率(ETR),在冬季落叶树CercissiliquastrumL.和常绿硬叶状灌木NeriumoleanderL.的成年和少年的完全暴露的成熟叶片中监测非光化学猝灭(NPQ)。所有植物都在明显相似的田间条件下生长。在这两个物种中,青少年在春季表现出比成年人低的ETR和增加的NPQ值,差异在夏季干旱期间加剧,在秋季减少。同时,幼鱼在春季和夏季显示出显着较高的基于叶绿素的总类胡萝卜素,这主要是由于对叶黄素循环成分(VAZ)的投资较高,结合增加的中午去环氧化状态(DEPS)和玉米黄质在黑暗中的部分保留。在夹竹桃中,尽管冬季青少年的ETR较低,两个年龄段的NPQ都非常低。总之,青少年表现出增强的光保护潜力,尤其是在夏天,由于它们的光化学能力降低。在有利的春季期间,成虫的光合优势可能归因于共存的生殖努力的需要。