Henan Key Laboratory of Germplasm Innovation and Utilization of Eco-Economic Woody Plant, Pingdingshan University, Pingdingshan, 467000, China.
Pingdingshan Academy of Agricultural Sciences/Henan Chinese Chive Engineering Technology Research Center, Pingdingshan, 467001, China.
BMC Plant Biol. 2023 Nov 28;23(1):595. doi: 10.1186/s12870-023-04615-y.
Stomatal variation, including guard cell (GC) density, size and chloroplast number, is often used to differentiate polyploids from diploids. However, few works have focused on stomatal variation with respect to polyploidization, especially for consecutively different ploidy levels within a plant species. For example, Allium tuberosum, which is mainly a tetraploid (2n = 4x = 32), is also found at other ploidy levels which have not been widely studied yet.
We recently found cultivars with different ploidy levels, including those that are diploid (2n = 2x = 16), triploid (2n = 3x = 24), pseudopentaploid (2n = 34-42, mostly 40) and pseudohexaploid (2n = 44-50, mostly 48). GCs were evaluated for their density, size (length and width) and chloroplast number. There was no correspondence between ploidy level and stomatal density, in which anisopolyploids (approximately 57 and 53 stomata/mm in triploid and pseudopentaploid, respectively) had a higher stomatal density than isopolyploids (approximately 36, 43, and 44 stomata/mm in diploid, tetraploid and pseudohexaploid, respectively). There was a positive relationship between ploidy level and GC chloroplast number (approximately 44, 45, 51, 72 and 90 in diploid to pseudohexaploid, respectively). GC length and width also increased with ploidy level. However, the length increased approximately 1.22 times faster than the width during polyploidization.
This study shows that GC size increased with increasing DNA content, but the rate of increase differed between length and width. In the process of polyploidization, plants evolved longer and narrower stomata with more chloroplasts in the GCs.
气孔的变化，包括保卫细胞（GC）密度、大小和叶绿体数量，常被用于区分多倍体和二倍体。然而，很少有研究关注多倍化过程中的气孔变化，特别是在一个植物物种内连续不同的倍性水平。例如，主要为四倍体（2n = 4x = 32）的葱属植物 Tuberosum 也存在其他尚未广泛研究的倍性水平。
我们最近发现了具有不同倍性水平的品种，包括二倍体（2n = 2x = 16）、三倍体（2n = 3x = 24）、拟五倍体（2n = 34-42，主要为 40）和拟六倍体（2n = 44-50，主要为 48）。评估了 GC 的密度、大小（长度和宽度）和叶绿体数量。倍性水平与气孔密度之间没有对应关系，其中异源多倍体（三倍体和拟五倍体中约为 57 和 53 个/平方毫米）的气孔密度高于同源多倍体（二倍体、四倍体和拟六倍体中分别约为 36、43 和 44 个/平方毫米）。倍性水平与 GC 叶绿体数量呈正相关（二倍体至拟六倍体中分别约为 44、45、51、72 和 90）。GC 长度和宽度也随倍性水平增加而增加。然而，在多倍化过程中，长度的增加速度大约比宽度快 1.22 倍。
本研究表明，GC 大小随 DNA 含量的增加而增加，但长度和宽度的增加速率不同。在多倍化过程中，植物进化出具有更多叶绿体的更长、更窄的气孔。
