Garrido Andreia, Conde Artur, Serôdio João, De Vos Ric C H, Cunha Ana
Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Centre for Environmental and Marine Studies (CESAM), Department of Biology, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
Plants (Basel). 2023 Jun 21;12(13):2393. doi: 10.3390/plants12132393.
Not only leaves but also other plant organs and structures typically considered as carbon sinks, including stems, roots, flowers, fruits and seeds, may exhibit photosynthetic activity. There is still a lack of a coherent and systematized body of knowledge and consensus on the role(s) of photosynthesis in these "sink" organs. With regard to fruits, their actual photosynthetic activity is influenced by a range of properties, including fruit anatomy, histology, physiology, development and the surrounding microclimate. At early stages of development fruits generally contain high levels of chlorophylls, a high density of functional stomata and thin cuticles. While some plant species retain functional chloroplasts in their fruits upon subsequent development or ripening, most species undergo a disintegration of the fruit chloroplast grana and reduction in stomata functionality, thus limiting gas exchange. In addition, the increase in fruit volume hinders light penetration and access to CO, also reducing photosynthetic activity. This review aimed to compile information on aspects related to fruit photosynthesis, from fruit characteristics to ecological drivers, and to address the following challenging biological questions: why does a fruit show photosynthetic activity and what could be its functions? Overall, there is a body of evidence to support the hypothesis that photosynthesis in fruits is key to locally providing: ATP and NADPH, which are both fundamental for several demanding biosynthetic pathways (e.g., synthesis of fatty acids); O, to prevent hypoxia in its inner tissues including seeds; and carbon skeletons, which can fuel the biosynthesis of primary and secondary metabolites important for the growth of fruits and for spreading, survival and germination of their seed (e.g., sugars, flavonoids, tannins, lipids). At the same time, both primary and secondary metabolites present in fruits and seeds are key to human life, for instance as sources for nutrition, bioactives, oils and other economically important compounds or components. Understanding the functions of photosynthesis in fruits is pivotal to crop management, providing a rationale for manipulating microenvironmental conditions and the expression of key photosynthetic genes, which may help growers or breeders to optimize development, composition, yield or other economically important fruit quality aspects.
不仅叶片，其他通常被视为碳汇的植物器官和结构，包括茎、根、花、果实和种子，也可能表现出光合活性。关于光合作用在这些“库”器官中的作用，目前仍然缺乏一个连贯且系统化的知识体系和共识。就果实而言，其实际光合活性受一系列特性影响，包括果实解剖结构、组织学、生理学、发育过程以及周围的微气候。在发育早期，果实通常含有高水平的叶绿素、高密度的功能性气孔和较薄的角质层。虽然一些植物物种在随后的发育或成熟过程中果实仍保留功能性叶绿体，但大多数物种会经历果实叶绿体基粒的解体和气孔功能的降低，从而限制气体交换。此外，果实体积的增加会阻碍光线穿透和二氧化碳的获取，也会降低光合活性。本综述旨在汇编与果实光合作用相关方面的信息，从果实特征到生态驱动因素，并解决以下具有挑战性的生物学问题：果实为何表现出光合活性以及其功能可能是什么？总体而言，有大量证据支持以下假说：果实中的光合作用对于在局部提供以下物质至关重要：ATP和NADPH，这两者对于多种高需求的生物合成途径（如脂肪酸合成）都是必不可少的；氧气，以防止其内部组织（包括种子）缺氧；以及碳骨架，其可为果实生长以及种子传播、存活和萌发所重要的初级和次级代谢产物的生物合成提供原料（如糖类、黄酮类化合物、单宁、脂质）。同时，果实和种子中存在的初级和次级代谢产物对于人类生活至关重要，例如作为营养、生物活性物质、油脂和其他经济上重要的化合物或成分的来源。了解果实中光合作用的功能对于作物管理至关重要，为调控微环境条件和关键光合基因的表达提供了理论依据，这可能有助于种植者或育种者优化果实的发育、成分、产量或其他经济上重要的果实品质方面。
