不同磷水平下4种柑橘砧木的生长状况、根系形态和生理特性

【目的】探索不同磷水平对柑橘砧木生长和根系形态及其相关生理特性的影响,为发掘磷高效柑橘砧木提供科学依据。【方法】以贵州喀斯特山地分布的野生宜昌橙(Citrus ichangensis Swingle)、酸橙(C.aurantiumL.)、白?檬(C.limonia Osbeck)和栽培种枳(Poncirus trifoliata Raf.)为材料,采用砂培方法研究不同磷水平(5、25和45 mg·L-1)下4种柑橘砧木的生长及生物量大小、根系形态特性、叶片和根系的酸性磷酸酶(Apase)及硝酸还原酶(NR)活性、根系分泌性酸性磷酸酶(SAPase)活性和根系的磷吸收动力学参数。【结果】在5 mg·L-1磷水平下,宜昌橙生长发育受到的抑制较小,其次为白?檬和酸橙,对枳的抑制最强。当营养液中磷浓度达到25mg·L-1时,宜昌橙和白?檬的株高、基径及鲜重和干重生物量、根系总长、总表面积、总体积和根尖数达到最大,5 mg·L-1的处理次之,45 mg·L-1的处理最小。随营养液中磷浓度的提高,酸橙和枳的上述指标和根冠比随之增大,宜昌橙和白?檬的根冠比则随之变小。在低磷条件下,宜昌橙的侧根粗度、二级侧根数量及密度和根冠比最大,叶片NR活性强弱顺序为宜昌橙白?檬酸橙枳,根系的NR活性强弱顺序为酸橙白?檬宜昌橙枳。不同砧木叶片和根系NR活性随供磷水平降低而明显减弱。在低磷胁迫下,砧木叶片及根系的APase活性和根系的SAPase活性响应强弱顺序为宜昌橙白?檬酸橙枳。在低磷条件下,宜昌橙的Imax大于白?檬、酸橙和枳,而Km和Cmin比白?檬、酸橙和枳的小。【结论】宜昌橙忍耐低磷胁迫的能力强,在低磷条件下根系形态和生理的适应性机制响应比其他3种柑橘砧木更加明显,表现出较强的磷吸收动力学特性。

Growth Status,Root Morphology and Physiological Characteristics of Four Citrus Rootstocks Under Different Phosphorus Levels Growth Status,Root Morphology and Physiological Characteristics of Four Citrus Rootstocks Under Different Phosphorus Levels

【Objective】Effects of different phosphorus (P) levels on the plants growth, roots morphology and related physiological characteristics of citrus rootstocks were studied for providing a scientific basis of high P efficiency citrus rootstocks excavation.【Method】The wild Citrus ichangensis Swingle, C. aurantium L., C. limonia Osbeck and cultivated species Poncirus trifoliata Raf. in Guizhou Karst mountain were used as materials, and the date including the growth and biomass, root morphological characteristics, activity of acid phosphatase (APase) and nitrate reductase (NR) of leaves and roots, and secretory acid phosphatase (SAPase) of roots and root absorption kinetics of P characteristics were researched through sand cultivation.【Result】The growth and development of C. ichangensis Swingle was less inhibited under 5 mg•L^-1 P level, followed by C. limonia Osbeck and C. aurantium L., restrained intensively to P. trifoliate Raf.. When P concentrations of nutrient solution was 25 mg•L^-1, the amount including the plant height, base diameter and fresh weight and dry weight of biomass, total root length, total surface area, total volume and total root tip reached the maximum for C. ichangensis Swingle and C. limonia Osbeck, followed by 5 mg•L^-1 P level, 45 mg•L^-1 P level was the minimum. With the P concentrations of nutrient solution increasing, the data including the plant height, base diameter and fresh weight and dry weight of biomass, total root length, total surface area, total volume, total root tip amount and root-shoot ratio of C. aurantium L. and P. trifoliata Raf. increased, however, the root-shoot ratio of C. ichangensis Swingle and C. limonia Osbeck decreased. Under low P conditions, C. ichangensis Swingle had the biggest lateral root roughness and the second lateral roots amount and root-shoot ratio, the NR activity in leaves was all in the order of C. ichangensis Swingle ＞C. limonia Osbeck ＞C. aurantium L. ＞P. trifoliata Raf., the NR activity in roots was all in the order of C. aurantium L. ＞C. limonia Osbeck ＞ C. ichangensis Swingle＞P. trifoliata Raf.. The NR activity in leaves and roots of different citrus rootstocks receded with P levels decreased significantly. The APase activity in leaves and roots, and the SAPase activity in roots was all in the order of C. ichangensis Swingle＞C. limonia Osbeck＞C. aurantium L. ＞P. trifoliata Raf. under low P stress. The I_max of C. ichangensis Swingle was greater than C. limonia Osbeck , C.aurantium L. and P. trifoliata Raf. under low P conditions, while the K_m and C_min was smaller than C. limonia Osbeck, C. aurantium L. and P. trifoliata Raf.【Conclusion】The ability to endure to low P stress of C. ichangensis Swingle was much stronger, and response of root morphology and physiological adaptation mechanisms were more obvious than the other three kinds of citrus rootstocks under low P conditions, which showed strong absorption characteristics of P dynamics.