水培富贵竹的根压及其影响因素

Root pressure of hydroponic Dracaena sanderiana and its determinants

木质部正压力(根压)在长期被低估之后,作为一种潜在的重要过程引起了人们的新兴趣,其可以恢复组织的水分,保持植物液压系统的功能和相互连接,并有助于细胞和组织的生长。该研究以株高60-80cm水培龙舌兰科富贵竹(Dracaena sanderiana)为研究对象,将压力传感器连接到茎干上端测量其根压,研究其昼夜节律变化以及温度、矿质元素(氮)、分蘖和去根等对其的影响,从而揭示根压在木质部水分向上运输中的重要作用。结果表明:(1)富贵竹的正根压全天存在,实验中测到的最大值为103 kPa,具有较明显的昼高夜低变化规律;(2)根压随水培温度下降而下降,水温为0℃时,根压几乎降低为0,根压的昼夜节律也随之改变;(3)不同浓度的硝酸盐(KNO_(3))处理均增加根压,但未改变昼夜节律;(4)具有分蘖的富贵竹茎干根压值比无分蘖的小,但也为正值;(5)剪掉全部须根后,根压迅速降为负值,但下降速率低于降温处理。综上所述,相较于其株高,大部分水培富贵竹全天存在的根部正压完全能够提供蒸腾耗水向上运输需要的动力,可以排除掉蒸腾拉力的影响。同时,水培富贵竹根压呈现出较稳定的节律变化,即昼高夜低,且受温度、氮含量、分蘖和去根等因素影响较为显著。

Aims Xylem positive pressure(root pressure)has gained new interests after a long period of underestimation,because it is important to restore tissue moisture,maintain function and interconnection of plant hydraulic system,and it contributes to cell and tissue growth.Methods In this study,hydroponic Dracaena sanderiana of 60-80 cm in height were used to study the circadian variation of root pressure and its determinants,in order to reveal the role that root pressure plays in the upward transport of water across xylem.Important findings(1)Positive root pressure of D.sanderiana existed throughout the day,and the maximum value obtained was 103 kPa,with a rhythm of high root pressure at daytime and low at night.(2)Root pressure decreased as water temperature declined,and at 0℃,root pressure reduced to nearly zero and the circadian rhythm was altered too.(3)Different concentrations of nitrate(KNO_(3))addition all increased root pressure,but the circadian rhythm was not altered.(4)Root pressure of stems with tillers was smaller(but still positive)than that of stems without tillers.(5)After completely cutting off the fibrous roots,root pressure quickly decreased to negative.In summary,the positive root pressure of most of the hydroponic D.sanderiana can fully provide the force needed to transport the water upwards to leaves throughout the day,and the force of transpirational pull is not needed.At the same time,the root pressure showed a relatively stable rhythm,that is,high at the day and low at night.Temperature,nitrogen content,tillers and root removing all had significant effects on root pressure.