不同遮阴处理对土坛树幼苗生长的影响

Effects of different shading treatments on the growth of Alangium salviifolium(Linn.f.)Wanger.seedlings

【目的】探讨不同遮阴环境对土坛树幼苗生长的影响,为培育土坛树优质种苗及其生长适应性研究提供理论依据。【方法】以2年生土坛树幼苗为试验材料,设不同遮阴处理,即透光率(75±5)%(L1处理)、透光率(50±3)%(L2处理)和透光率(25±5)%(L3处理),以全光照为对照(CK),研究光照对土坛树幼苗生长、生物量分配、叶绿素含量及光合生理等指标的影响。【结果】在不同遮阴环境下,L1、L2和L3处理植株基径生长低于CK,而株高高于CK;同时,L2和L3处理植株叶片的叶长、叶宽、叶厚和叶柄长均高于CK;L3处理植株生长增量最大,其株高、叶长、叶宽、叶厚和叶柄长指标分别比CK提高82.59%、90.43%、80.09%、21.14%和62.11%;相较于CK,土坛树幼苗总生物量积累随遮阴程度的增加而升高,且生物量积累主要集中于地上部分,尤其是叶部分积累最多,其中L2和L3处理叶生物量分别增加201.32%和312.52%,而其地下生物量积累与CK无显著差异(P>0.05);土坛树幼苗叶绿素a(Chla)、叶绿素b(Chlb)及总叶绿素[Chl(a+b)]含量与遮阴程度呈正相关,叶绿素a/b(Chla/b)比值变化则相反;不同遮阴环境下Chla、Chlb和Chl(a+b)含量排序为:L3处理>L2处理>L1处理;各遮阴处理土坛树幼苗净光合速率(Pn)和蒸腾速率(Tr)较CK均呈现不同程度升高,L1、L2和L3处理间,胞间CO2浓度(Ci)随着光合作用的增强而逐渐下降,气孔导度(Gs)则逐渐升高;遮阴处理提高了土坛树幼苗的水分利用率(WUE)。【结论】2年生土坛树幼苗有较强的耐阴能力,25%~50%透光率处理对幼苗的促生效果较为明显,其中25%透光率最有利于幼苗生长;土坛树幼苗可通过调整自身形态结构,同时减少基径生长量的分配,增加地上部分特别是叶部分的生物量,提高其光能利用效率。

【Objective】To explore effects of different shading environments on the growth of seedlings of Alangium salviifolium(Linn.f.)Wanger.,and analyze their responses to the shading,then provide a theoretical basis for breeding fine germchits and its growth adaptability research.【Method】Seedlings of two-year-old A.salviifolium were used as the test materials,with CK treatment(full light was used as the control),L1 treatment[light transmittance(75±5)%],L2 treatment(light transmittance 50%±3%)and L3 treatment[light transmittance(25±5)%]were set,and the growth,biomass allocation,chlorophyll content and photosynthetic physiology indexes of A.salviifolium seedlings under different shading treatments were measured.【Result】Under different shading conditions,the basal diameter of L1,L2 and L3 were lower than the CK,while the plant height was higher than the CK.Meanwhile,the growth of leaf length,leaf width,leaf thickness and petiole length of L2 and L3 were markedly higher than the CK treatment;L3 treatment had the largest growth increment and its indexes of plant height,leaf length,leaf width,leaf thickness and petiole length were increased by 82.59%,90.43%,80.09%,21.14%and 62.11%than CK,respectively.Compared to the CK treatment,the total biomass accumulation of A.salviifolium seedlings increased with the increase of shading intensity,which was mainly concentrated in the aerial part,especially in the leaf part,and the leaf biomass of L2 and L3 treatments increased by 201.32%and 312.52%respectively.However,as for the underground biomass,there was no significant difference between L1,L2 and L3 treatments and the CK treatment(P>0.05).The content of chlorophyll a(Chla),chlorophyll b(Chlb)and total chlorophyll of A.salviifolium seedlings was positively correlated with the degree of shading,while the content of chlorophyll a/b(Chla/b)changed in the opposite way.Among different shading treatments,the order of chla,chlb and chla+b was L3>L2>L1.Compared to the CK treatment,the net photosynthetic rate(Pn)and transpiration rate(Tr)of A.salviifo-lium seedlings increased to different degrees.During the treatments of L1,L2 and L3,the intercellular CO2 concentration(Ci)gradually decreased with the increase of Pn,while the stomatal conductance(Gs)gradually increased;meanwhile,shading treatment improved the water use efficiency(WUE)of A.salviifolium seedlings.【Conclusion】The 2-year-old A.salviifolium seedlings have strong shade-tolerance,and 25%-50%light transmittance treatment has obvious effect on its growth promotion,among which 25%light transmittance is the most conducive to the growth of seedlings.Additionally,A.salviifolium seedlings can increase the Pn through adjusting its morphological structure,reducing the distribution of basal diameter growth,and increasing the biomass of above-ground parts,especially leaf parts.