General Botany Laboratory, Adam Mickiewicz University, Faculty of Biology, Institute of Experimental Biology, Umultowska 89, Poznań, Poland.
Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, Poland.
Tree Physiol. 2019 Apr 1;39(4):573-589. doi: 10.1093/treephys/tpy145.
The correlations of phenotypic traits with environmental drivers suggest that variability of these traits is a result of natural selection, especially if such trait correlations are based on genetic variability. We hypothesized that in situ correlations of structural needle traits of Scots pine (Pinus sylvestris L) with minimal winter temperature (Tmin) reported previously from a temperate/boreal transect would be conserved when plants are cultivated under common conditions. We tested this hypothesis by analyzing needles from two common gardens located in the temperate zone, one including adult trees and the other juvenile seedlings. The majority of adult needle traits for which correlations with Tmin were found in the field turned out to be under environmental influence. In contrast, the majority of traits studied in juvenile needles were correlated with the original Tmin suggesting the role of past natural selection in shaping their variability. Juvenile needles thus appeared to be inherently less plastic than adult needles, perhaps reflecting the stronger selective pressure acting during juvenile, as compared with adult, ontogenetic stage. Genetically based cold-climate adaptation in either juvenile or adult needles, or both, involved an increase in leaf mass per area and leaf density, decrease in needle length, reduction in the amount of xylem and phloem, increase in thickness of epidermis, decrease in tracheid diameter and increase in tracheid density, and increase in diameter and volume fraction of resin ducts. We also show that at least some traits, such as transverse xylem and phloem areas and number of fibers, scale with needle length, suggesting that climate-related trait variation may also be mediated by changes in needle length. Moreover, slopes of these allometric relationships may themselves be plastically modified. The phenotypic syndrome typical of needles from cold environments may thus be under environmental, genetic and allometric control.
表型特征与环境驱动因素的相关性表明，这些特征的可变性是自然选择的结果，特别是如果这些特征相关性基于遗传可变性。我们假设，在温带/北方的一个横断面上先前报道的与最小冬季温度（Tmin）相关的苏格兰松（Pinus sylvestris L）结构针性状的原位相关性在植物在常见条件下种植时将保持不变。我们通过分析位于温带地区的两个普通花园中的针来测试这个假设，一个包括成年树，另一个包括幼年树苗。在野外发现与 Tmin 相关的大多数成年针叶特征结果都受到环境的影响。相比之下，在幼年针叶中研究的大多数特征与原始 Tmin 相关，表明过去自然选择在塑造其变异性方面的作用。因此，幼年针叶似乎比成年针叶固有地更具可塑性，这可能反映了在幼年与成年发育阶段相比，更强的选择压力。无论是在幼年还是成年针叶中，或者两者都具有基于遗传的对寒冷气候的适应，都涉及叶片面积和叶密度的增加、针叶长度的减少、木质部和韧皮部的减少、表皮厚度的增加、导管直径的减少和导管密度的增加，以及树脂管的直径和体积分数的增加。我们还表明，至少一些特征，如横向木质部和韧皮部面积以及纤维数量，与针叶长度成比例，表明与气候相关的特征变化也可能受到针叶长度的变化的介导。此外，这些异速关系的斜率本身可能也具有塑性。因此，来自寒冷环境的针叶的表型综合征可能受到环境、遗传和异速关系的控制。
