Abstract:

Rice leaves, as the primary source of dry matter production and grain yield, exhibit a range of physiological functions, including photosynthesis, respiration, and transpiration. These leaves can be divided along the main vein, revealing distinct morphological and physiological traits on each side, such as variations in width, thickness, SPAD value, and nitrogen content, which manifest a striking and unique lateral asymmetry. Symmetry and asymmetry are widespread in nature, with biological asymmetry being categorized into three types: fluctuating asymmetry, directional asymmetry, and antisymmetry. Existing research has shown that rice leaf lateral asymmetry belongs to directional asymmetry, where one side of the main vein is wider, thicker, and rougher than the other, and also exhibits a lower SPAD value and nitrogen content. Moreover, the tillering characteristic of rice plants imparts a distinct location distribution to the lateral asymmetry of its leaves. Notably, within a rice population, the smooth side (the narrower and thinner side) of the leaf has an almost equal probability (approximately 50%) of appearing on either the left or the right. As such, the location distribution characteristics of rice leaf lateral asymmetry can be considered as exhibiting fluctuating asymmetry with an ideal distribution probability of 50%. Furthermore, certain regulatory genes that influence rice leaf width also affect the degree of rice leaf lateral asymmetry. One such gene is Leaf Lateral Symmetry 1 (LSY1), which has been clearly linked to rice leaf lateral asymmetry. In this paper, we review the progress of research on rice leaf lateral asymmetry from morphological, physiological, and genetic standpoints, and classify rice leaf transverse asymmetry into four levels: single leaf, single stem, single plant, and population. However, there is a limited amount of literature on rice leaf transverse asymmetry in the fields of crop science and plant physiology, and further exploration is needed to determine whether it significantly impacts rice yield and quality.

Key words: rice, leaf, asymmetry, morphological traits, physiological traits

摘要：

水稻叶片承载着光合作用、呼吸作用和蒸腾作用等多重生理功能，是干物质积累和籽粒产量的主要贡献者。沿主脉剖分，水稻叶片可一分为二，其两侧在宽度、厚度、SPAD值（叶绿素相对含量）及氮含量等形态与生理特性上表现出显著的差异，呈现出一种独特而明显的横向不对称性。在自然界中，对称和不对称性普遍存在，而生物发育过程中的不对称性被细分为波动不对称、单向不对称和双向不对称三大类。现有研究表明，水稻叶片的横向不对称性属于单向不对称，即主脉的一侧相较于另一侧更宽、更厚、更粗糙，同时SPAD值和氮含量也相对较低。此外，由于水稻植株具有分蘖的生长特性，这使得水稻叶片的横向不对称性在位置分布上呈现出特有的规律。在水稻群体中，叶片的光滑侧（即窄侧和薄侧）无论是居左还是居右，其概率均接近50%。基于此，我们可以将水稻叶片横向不对称性的位置分布特征与这一50%的理想分布概率视为一种波动不对称的表现。从现有文献资料来看，水稻叶宽的部分调控基因也对叶片的横向不对称性程度产生着影响。其中，Leaf lateral symmetry 1（LSY1）是目前已知并明确报道的与水稻叶片横向不对称性相关的调控基因。本文从形态、生理和遗传等方面综述了水稻叶片横向不对称性的研究进展，并将其分为单叶、单茎、单株和群体四个层次进行深入探讨。关于水稻叶片横向不对称性在作物学和植物生理学方面的研究文献相对匮乏，其对水稻产量和品质可能产生的显著影响尚需进一步的深入探索和研究。

关键词: 水稻, 叶片, 不对称性, 形态性状, 生理性状