沙培条件下磷、 钾、 钙亏缺对枳（Poncirus trifoliata）幼苗根系形态及营养吸收的影响

【目的】根系是吸收水分和养分的主要器官，对于多年生木本果树的生长发育尤为重要。由于果树根系庞大、 分布错综复杂，对根系构型和空间分布等的研究相对较少。本文利用计算机扫描系统及其图像分析软件观测根系二维形态参数，并用原子吸收法测定植株养分含量，以探索养分亏缺对枳根系形态的影响，以及根系形态变化与植株养分吸收的关系。【方法】本试验在沙培条件下，以柑橘砧木枳(Poncirus trifoliata)实生苗为试材，研究了缺磷、 钾和钙对其根系形态以及植株体内营养元素含量的影响。利用爱普生数码扫描仪（Expression 10000XL 1.0, Epson Inc. Japan）扫描根系，并用WinRhizo Pro (S) v. 2004b软件(Regent Instruments Inc., Canada)分析获取根系总长、 总体积和总表面积等二维形态参数。利用原子吸收光谱仪(SPECTR AA220)测定样品K、 Ca、 Mg、 Fe、 Cu、 Zn等元素含量。【结果】从扫描数据可知，3 种缺素处理对枳幼苗根系形态结构有较大的影响，即在缺素时根系总长、 表面积和体积均显著降低，缺P处理使枳实生苗粗根的根系长度、 表面积、 体积显著降低,但是增加了中等粗根的表面积和体积； 缺K和缺Ca处理的中等粗根根系长度、 表面积和体积均显著低于对照； 3种缺素处理均显著降低了细根和粗根的根系长度、 表面积和体积。不同缺素处理对植株根系和地上部生长的影响也存在差异，缺P对地上部的抑制作用显著强于根系，缺K处理对根系生长的抑制作用较强，缺Ca对根系和地上部生长的抑制作用均较小。缺Ca处理植株体内Zn和Fe浓度均显著增加但Ca浓度降低，缺P时植株体内Ca和地上部Zn浓度增加，而缺K时植株体内Ca、 Zn浓度增加但Fe和K浓度均显著降低。【结论】不同缺素条件下枳实生苗根系形态各异，导致根系对不同养分的吸收能力不同，从而使植株体内K、 Ca、 Zn、 Fe等养分含量发生改变，最终影响整个植株根系和地上部的生长，表现出各缺素环境所特有的树体特征。

Effects of P,K and Ca deficiency on the root morphology and nutrient absorption of Poncirus trifoliata seedlings

【Objectives】Root system is particularly important for the  nutrient and water uptake  of fruit trees. Few researches are reported on the root architecture and spatial distribution related to nutrition  because of the hugeness and complex of root distribution. In this research, Epson digital scanner and plasma atomic emission spectroscopy were used to study the two-dimensional architecture and nutrient concentration of plant roots, to explore the  effects of nutrient deficiency on root morphology and the relationship with plant nutrient uptake.【Methods】A  sand culture pot experiment was conducted and the seedlings of Poncirus trifoliata were grown  as test materials. Root samples were scanned with an Epson digital scanner (Expression 10000XL 10, Epson Inc. Japan) and the data were analyzed with the WinRhizo Pro (S) v. 2004b software (Regent Instruments Inc., Canada) to obtain the root length, root volume and root surface area. The concentrations of nutrients were determined by inductively coupled plasma atomic emission spectroscopy (Thermo Inc, IRIS Advan, United States).【Results】The total root length, surface areas and volumes are reduced significantly in the nutrient deficiency media. When the root system was classified into fine, middle and coarse roots according to their diameters, the effects of nutrient deficiencies on the three fractions were different with treatments. Compared with the control,   the root length, surface area and volume of fine and coarse roots are reduced, but the surface area and volume of middle roots are increased remarkably under P deficiency;   the root length, surface area and volume of fine and middle roots are reduced under K and Ca deficiency. The nutrient deficiencies induce significant decreases of shoot and root biomass, stronger inhibition effect on shoot than on root under the P deficiency, but opposite effect under K deficiency, least effect under Ca deficiency. The Zn concentrations of plants are significantly increased under three nutrient deficiency media, the Fe concentration increased under the Ca deficiency but decreased under the K deficiency, Ca concentrations increased under the P and K deficiencies but decreased under the Ca deficiency.【Conclusions】The nutrient deficiencies lead to worse root morphology, as a concequence, decreases the absorption of nutrients in different extents and the growth of plant root and shoot, and leads to the peculiar  symptoms corresponding to the different nutrient deficiency environment.