重茬胁迫下苹果不同砧木幼苗生长及根系吸收的差异

Differences of growth and root absorption of different apple rootstock seedlings in replant stress

【目的】选择合适砧木是防治苹果重茬障碍最有前途的方法之一。本研究比较了三种苹果砧木的幼苗在重茬胁迫下的生长及根系吸收的差异,探讨重茬胁迫对K+、Ca2+吸收的影响,为筛选抗重茬砧木材料和培育抗重茬砧木品种提供理论依据。【方法】以平邑甜茶(Malus hupehensis Rehd.)、新疆野苹果[Malus sieversii(Ledeb.)Roem.]和富平楸子[Malus prunifolia(Willd.)Borkh.]一年生实生苗为试材,取自泰安市道朗镇玄家庄20年红富士/八棱海棠老果园原树穴深0—40 cm的根际土作为试验用土,于2012年4月25日取砧木幼苗并分为两组,一组利用非损伤微创技术测定根际K+、Ca2+离子流,根系固定于平衡液中,平衡半小时后测定重茬胁迫前的根际离子流速,然后将其在重茬土提取液中浸泡半小时,测定重茬胁迫后的根际离子流速;另一组移栽至直径为25cm、深30cm的苗盆中,7 9月分别测定植株株高、径粗、叶绿素含量和光合速率;生长季结束后扫描根系结构,分别称量幼苗根系、枝条、叶片的鲜重和干重。【结果】三种砧木幼苗受到重茬胁迫后,地上部生长受到不同程度抑制。重茬胁迫前后平邑甜茶株高差异不显著,新疆野苹果和富平楸子株高胁迫后均显著降低;新疆野苹果光合速率重茬土显著低于正茬土,其它两种砧木光合速率在胁迫前后无显著差异;叶绿素含量均表现为重茬土显著低于正茬土;径粗在胁迫前后无显著差异。重茬土中新疆野苹果根系干物质积累下降明显,根/冠比增大;三种砧木的根系生长量显著增大,根系总长度分别是正茬土中根系总长度的1.45倍、2.22倍、1.71倍;三种砧木幼苗在重茬土中的根系活力均低于正茬,但胁迫前后平邑甜茶根系活力下降幅度最小。重茬胁迫后,三种砧木的根际K+离子流均由内流转变为外排,胁迫前后平邑甜茶的根际K+离子平均流速变化较小,说明对其影响小,新疆野苹果根际K+离子平均流速变化最为明显,其吸收K+能力最弱;平邑甜茶根际Ca2+流动方向在胁迫前后未发生变化,均为内流,而另外两种砧木根际Ca2+离子流均由内流转变为外排,且新疆野苹果根际Ca2+离子平均流速变化最为明显。【结论】苹果砧木在重茬胁迫下地上部生长受到显著性抑制,根系总量增大,K+、Ca2+的吸收受到不同程度的影响;重茬使抗性较差的砧木新疆野苹果的物质积累受到较严重的阻碍,根冠比显著增加,K+、Ca2+的吸收受到严重影响;较耐重茬的砧木平邑甜茶的根冠比相对稳定,K+、Ca2+的吸收受到的影响也最小;富平楸子的表现介于两者之间。

[Objective] Selecting appropriate rootstocks is one of the most effective methods of preventing apple from replant disease. In order to provide theoretic foundation for screening of anti-replant rootstock materials and＆amp;nbsp;breeding anti-replant rootstock varieties, differences of growth and root absorption of three apple rootstock seedlings were compared, and absorption of potassium and calcium ions under the replant stress was discussed in this study.[Methods] One-year-old seedlings of Malus hupehensis Rehd, Malus sieversii（ Ledeb. ） Roem and Malus prunifolia （ Willd. ） Borkh were used as the materials, and 0-40 cm rhizosphere soil of 20 years’ orchard which‘Fuji’ apple on M . robusta stock located in Tai’an city was used as matrix. The seedlings were divided into two parts, some of the seedlings were supplied to determine the flow velocity of rhizosphere K＋ and Ca2＋ under the replant stress by Non-invasive Micro-test Technique on April 25 , 2012 , other seedlings were transplanted into pots of 25 cm wide and 30 cm deep. The height, stem diameter, chlorophyll content and photosynthetic rate of the seedlings were investigated from July to September. The root structure was scanned and dry weight and fresh weight of roots, branches and leaves were measured respectively after the growing season. [Results]The aboveground growth of the three rootstocks is suppressed in different levels under the replant stress. The heights of M. hupehensis have no significant differences before and after the replant stress, while the heights of the other two rootstocks are significantly decreased. The photosynthetic rates have no significant decreases except M. Sieversii. The chlorophyll contents of three rootstocks are significantly decreased and there are no obviously changes in stem diameter. The dry matter of M. sieversii seedlings is significantly decreased under the replant stress, while the root-shoot ratio is increased. Root biomass amounts of the three rootstocks are increased observably and the total root lengths are increased to 1. 45 times, 2. 22 times, 1. 71 times, respectively compared to the control. Root activities of the three rootstocks are all decreased, which the one of M. hupehensis fell less than those of the other two rootstocks. The flow velocity of K＋ changes from inward to outward under the replant stress and has a little change for M. hupehensis, in contrast, there is significant change in the average ion flow rate of K＋for M. sieversii. The velocity direction of Ca2＋has no change for M. hupehensis, and the velocity direction of Ca2＋of the other two rootstocks changes into outward from inward, and the most significant change in the flow velocity of Ca2＋appears in M. sieversii.[Conclusion]The shoot growth of apple rootstocks is significantly inhibited and the amounts of roots are increased. The absorption of K＋ and Ca2＋ affected by different degree. As the less tolerant rootstocks, M. Sieversii’s dry matter accumulation is seriously constrained and the root-shoot ratio is significantly increased, and the absorptions of K＋and Ca2＋was also severely affected. M. hupehensis has a stronger resistance, its root-shoot ratio was relatively stable, as well as the absorptions of K＋ and Ca2＋are affected minimally. The performance of M. prunifolia is in middle.