3种倍性青杨扦插苗对覆膜滴肥的生长响应

Response of Populus cathayana cutting seedlings of three ploidy types to fertilizer under film mulching and drip irrigation

【目的】研究指数施肥与常规施肥在覆膜滴灌形式下对1年生多倍体青杨(Populus cathayana)扦插苗生长、根系形态、生物量积累和光合作用的影响,选出更适合其生长规律的滴肥方式,旨在提高多倍体青杨扦插苗质量的条件下缩短苗木生长周期,为不同倍性青杨扦插苗水肥管理提供理论依据。【方法】以2倍体、3倍体和4倍体1年生青杨扦插苗为对象,设置覆膜滴灌下指数施肥(8.01 g/株,EF)、常规施肥(7.98 g/株,CF)和不施肥(CK) 3种处理。每次施肥前测定青杨扦插苗苗高和地径,绘制生长曲线。在生长旺盛期进行生理指标的测定,最终收获苗木后,分离根系对其进行扫描,获得根系形态指标。最后烘干苗木根、茎、叶测定各器官生物量。【结果】生长结束时与指数滴肥处理相比,常规滴肥处理更显著地促进青杨扦插苗生长,苗高和地径分别比对照增加27.80%和13.81%(P<0.05),多倍体(3倍体、4倍体)苗木各营养器官生物量显著增加,4倍体青杨插条根系生物量最高为25.73g。主要表现在多倍体苗木根系长度、根系直径、根系表面积、根系体积和根尖数量分别显著高出对照182.60%、32.97%、122.02%、119.48%和178.25%(P<0.05),且各指标从大到小依次为3倍体>4倍体>2倍体植株的。常规滴肥下多倍体叶片叶绿素含量较对照显著高出14.66%,苗木单株光合产量较对照显著高出38.79%,且各指标从大到小依次为4倍体>3倍体>2倍体。覆膜常规滴肥苗木气孔导度低于指数滴肥,但却保持着较高的胞间CO2浓度,其中多倍体植株气孔导度大于2倍体植株的。【结论】覆膜滴肥情况下,常规滴肥更有助于促进多倍体青杨扦插苗生长,3倍体和4倍体植株生长差异不大。

【Objective】 Effects of exponential fertilization(EF) and conventional fertilization(CF) with film mulching and drip irrigation on the aboveground growth, root morphology, biomass allocation and photosynthesis of one-year-old Populus cathayana seedlings were investigated in this study to shorten the growth cycle of seedlings under the conditions of improving the quality of P. cathayana polyploidy seedlings and provide a theoretical basis for water and fertilizer management of P. cathayana cutting seedlings of different ploidy types. 【Method】A nitrogen fertilization experiment was conducted with one-year-old diploid, triploid and tetraploid P. cathayana cutting seedlings under drip irrigation with plastic film mulching. Further, three treatments with film mulching and drip irrigation were applied: exponential fertilization(8.01 g per seedling, EF), constant fertilization(7.98 g per seedling, CF), and non-fertilization(CK). We fertilized one-year-old P. cathayana seedlings every 15 days from the end of May by drip irrigation facilities, and seven times in the whole seedling growth period. During the experimental period, the height and base diameter of the seedlings were measured before each fertilization, and the data were used to plot the growth curve. Photosynthesis was measured during the period of vigorous growth, including chlorophyll content, net photosynthetic rate(Pn), stomatal conductance(Gs), intercellular CO2 concentration(Ci), and transpiration rate(Tr). When these P. cathayana seedlings were harvested, roots were separated from the plants for scanning and calculating their morphological indices, namely, root length, diameter, surface area, volume and tips. After drying, the biomass of the roots, stems and leaves of each cutting seedling was determined.【Result】By the end of the growing season, CF promoted the growth of P. cathayana one-year-old cutting seedlings more significantly than EF did, and the seedling height and ground diameter were significantly increased by 27.80% and 13.81%, respectively(P < 0.05). The biomass of P. cathayana one-year-old cutting seedlings with polyploid(the triploid and tetraploid seedlings) under CF treatment increased significantly;the biomass of roots, stems and leaves of seedlings treated with CF was significantly higher than that of CK by 102.25%, 191.02% and 102.90%, respectively(P < 0.05);and the biomass of roots of tetraploid P. cathayana cuttings was the highest at 25.73 g. The root length, diameter, surface area, volume and tips of polyploid seedlings under CF treatment was 182.60%, 32.97%, 122.02%, 119.48% and 178.25% higher than those of CK, respectively(P < 0.05), and those with different ploidy types were in the order triploid > tetraploid > diploid. Chlorophyll content and photosynthetic yield per stem of polyploid seedlings under CF treatment were 14.66% and 38.79% greater than those of CK, respectively(P < 0.05), and the order of those with different ploidy types was tetraploid > triploid > diploid. The Gs of P. cathayana one-year-old cutting seedlings under CF treatment were lower than those of EF but maintained a high Ci. The Gs of the polyploid seedlings of both EF and CF were higher than those of diploid seedlings, indicating that polyploid P. cathayana one-year-old cutting seedlings could maintain a high photosynthetic physiological process while reducing water transpiration. 【Conclusion】Constant fertilization regimes under film mulching and drip irrigation effectively promoted the growth of P. cathayana one-year-old cutting seedlings, and no significant difference between triploid and tetraploid seedlings was observed.