供磷水平对棕榈幼苗生长及根系形态的影响

以1年生棕榈幼苗为试验材料,设置0、0.5、1.0、1.5 mmol·L^-14个供磷水平,采用沙培试验,处理150 d后测定棕榈苗木生长指标、根系形态指标。结果表明:供磷水平为1 mmol·L^-1时,苗高增量、比叶面积、生物量、根冠比均达到最大值,且随着供磷水平的继续增加上述指标开始降低;棕榈根系的总根长、总表面积、根尖数量、组织密度均在1 mmol·L^-1时达到最大,当磷浓度为1.5 mmol·L^-1时,棕榈根系生长受阻;根毛是棕榈响应磷缺乏最敏感的指标,缺磷处理(0 mmol·L^-1)下,棕榈幼苗根毛数量、总长度均达到最大值。低磷水平下,棕榈通过改变根毛的吸收面积来增强对水分养分的吸收。综上所述,磷浓度高于或低于1 mmol·L^-1,都不利于棕榈幼苗的生长,最适宜棕榈幼苗正常生长的磷肥需要量为1 mmol·L^-1。

Effects of Phosphorus Levels on Growth and Root Morphology of Trachycarpus fortunei Seedlings

Four phosphorus supply levels(0, 0.5, 1 and 1.5 mmol·L^-1) were designed for the test of 1-a seedlings of Trachycarpus fortunei as test materials. The growth index and root morphology index of T. fortunei seedlings were measured after 150 d treatment by sand culture test. When the phosphorus supply level was 1 mmol·L^-1, the increment of seedling height, specific leaf area, biomass and root-cap ratio all reached the maximum, and the above indexes began to decrease with the increase of phosphorus supply level. The total root length, surface area, number of root tips and tissue density of T. fortunei root all reached the maximum at 1 mmol/L. When the phosphorus concentration was 1.5 mmol·L^-1, the growth of T. fortunei root was hindered. Root hair is the most sensitive index of T. fortunei to phosphorus deficiency. Under phosphorus deficiency treatment(0 mmol·L^-1), root hair number and total length of T. fortunei seedlings reached the maximum. Under low phosphorus levels, T. fortunei can enhance water and nutrient absorption by changing root hair absorption area. Phosphorus concentration higher or lower than 1 mmol·L^-1 is not conducive to the growth of T. fortunei seedlings. The optimum phosphorus fertilizer requirement for normal growth of T. fortunei seedlings is 1 mmol·L^-1.