Fanourakis Dimitrios, Heuvelink Ep, Carvalho Susana M P
Wageningen University, Department of Plant Sciences, Horticulture and Product Physiology Group, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
Funct Plant Biol. 2015 Jul;42(8):737-745. doi: 10.1071/FP15008.
Within-leaf heterogeneity in stomatal traits poses a key uncertainty in determining a representative value for the whole leaf. Accounting for this heterogeneity, we studied stomatal initiation on expanding leaves and estimated stomatal conductance (gs) of mature leaves. The entire lamina was evaluated at four percentages of full leaflet elongation (FLE; leaflet length relative to its final length) in Rosa hybrida L. plants grown at 60% relative air humidity (RH), and at 100% FLE following cultivation at elevated (95%) RH. Over 80% of the stomata were initiated between 33 and 67% FLE, whereas stomatal growth mostly occurred afterwards. At 100% FLE, the heterogeneity in stomatal density was the result of uneven stomatal differentiation, while an uneven differentiation of epidermal cells contributed to this variation only at elevated RH. Noticeable within-leaf differences (up to 40%) in gs were calculated at 100% FLE. Avoiding leaflet periphery decreased this heterogeneity. Despite the large promotive effect of elevated RH on stomatal and pore dimensions, the within-leaf variation remained unaffected in all characters, besides pore aperture (and, thus, gs). The noted level of within-leaf variation in stomatal features demands a sampling scheme tailored to the leaf developmental stage, the feature per se and the evaporative demand during growth.
叶片气孔性状的叶内异质性给确定整个叶片的代表性值带来了关键的不确定性。考虑到这种异质性，我们研究了正在扩展的叶片上的气孔起始情况，并估算了成熟叶片的气孔导度（gs）。在相对空气湿度（RH）为60%的条件下生长的杂交蔷薇植株中，在小叶全长伸长（FLE；小叶长度相对于其最终长度）的四个百分比时对整个叶片进行评估，并在高湿度（95%）条件下培养后在100% FLE时进行评估。超过80%的气孔在FLE为33%至67%之间起始，而气孔生长大多在这之后发生。在100% FLE时，气孔密度的异质性是气孔分化不均匀的结果，而表皮细胞的不均匀分化仅在高湿度条件下才导致这种变化。在100% FLE时计算得出叶片内gs存在显著差异（高达40%）。避开小叶边缘可降低这种异质性。尽管高湿度对气孔和孔隙尺寸有很大的促进作用，但除了孔隙孔径（以及由此产生的gs）外，所有性状的叶内变异均未受影响。所指出的气孔特征的叶内变异水平要求根据叶片发育阶段、特征本身以及生长期间的蒸发需求制定抽样方案。
