年龄效应对白杨硬枝扦插苗生长及其茎皮部解剖结构和叶片生化指标的影响

为探究白杨年龄效应导致的扦插繁殖苗退化问题，该试验以杂种三倍体‘北林雄株２号’的不同年龄苗木硬枝插穗为材料，就扦插苗生长形态、光合生理、根发育特征、插穗皮部解剖结构以及苗木生长发育过程中叶片可溶性总糖（ＴＳＳ）、可溶性总蛋白（ＴＳＰ）、叶绿素（Ｃｈｌ）、脯氨酸（Ｐｒｏ）、赤霉素（ＧＡ）、生长素（ＩＡＡ）、脱落酸（ＡＢＡ）及ＩＡＡ／ＡＢＡ比值等生理生化指标进行了观测。结果表明（１）再生苗苗高、地径、叶柄长度、节间宽、叶面积、主根数、主根长、生根率、根系效果指数及净光合速率（Ｐｎ）等指标均随插穗年龄的增加而降低，而其侧根数、侧根长、胞间ＣＯ２浓度（Ｃｉ）、气孔导度（Ｇｓ）和蒸腾速率（Ｔｒ）等指标与插穗年龄无明显相关性。（２）插穗茎皮部解剖结构显示，周皮和木质部厚度都随插穗年龄增大而增厚，韧皮部厚度则无明显变化。（３）再生苗叶片可溶性总糖、总蛋白、叶绿素、ＩＡＡ、ＧＡ含量以及ＩＡＡ／ＡＢＡ比值等指标均随插穗年龄的增加而逐渐降低，而脯氨酸和ＡＢＡ含量则随插穗年龄增加而增加。研究发现，白杨扦插苗随插穗年龄的增加累积成熟效应，使新生苗表现出整体性衰老的生长状态。

To investigate the decline of cutting-propagated poplar seedlings caused by age effect, this experiment used hardwood cuttings collected from seedlings of different ages of the triploid hybrid poplar 'Beilin Xiongzhu No.2' as experimental materials. We observed the growth morphology, photosynthetic physiology, root development characteristics, anatomical structure of the cutting bark, and a series of physiological and biochemical indicators in leaves during seedling growth and development, including total soluble sugar (TSS), total soluble protein (TSP), chlorophyll (Chl), proline (Pro), gibberellin (GA), auxin (IAA), abscisic acid (ABA), and the IAA/ABA ratio. The results showed that: (1) Indicators such as seedling height, ground diameter, petiole length, internode width, leaf area, number of main roots, main root length, rooting rate, root effect index, and net photosynthetic rate (Pn) of regenerated seedlings decreased with the increase of cutting age, while indicators including number of lateral roots, lateral root length, intercellular CO2 concentration (Ci), stomatal conductance (Gs), and transpiration rate (Tr) showed no significant correlation with cutting age. (2) Anatomical observation of the cutting stem bark revealed that the thickness of both the cork layer and xylem increased with the advancement of cutting age, whereas the phloem thickness exhibited no obvious change. (3) The contents of total soluble sugar, total soluble protein, chlorophyll, IAA, GA, and the IAA/ABA ratio in the leaves of regenerated seedlings all gradually declined with the increase of cutting age, while the contents of proline and ABA increased along with the rise of cutting age. This study demonstrated that poplar cutting-propagated seedlings accumulate mature effects as the cutting age increases, leading the new seedlings to present a growth state of overall senescence.