植物膜转运的模型预测、实验验证及生理学影响

胞膜是控制细胞振荡的中心，细胞的振荡在植物界中十分普遍。例如质膜电位的周期性变化、液泡电位及电流的波动、质外体的浓度变化、胞内pH及Ca2+的波动、不同细胞类型质膜跨膜离子流振荡等。然而，目前除了大致了解膜和离子流直接或间接参与振荡过程，研究人员对这种振荡的生理学功能仍然知之甚少。 Shabala等研究人员应用反馈受控振荡模型提出了许多设想：（1）振荡周期强烈依赖于质子泵活性；（2）质子泵活性受抑制时，振荡停止；（3）H+和K+流之间存在方向性的转变；（4）细胞膜上有对外界温度和离子浓度变化感受的“窗口”，对外界不同的变化细胞表现为不同的振荡模式；（5）振荡特性与细胞大小紧密相关等。他们使用“非损伤微测技术”直接测定了不同环境条件下植物根、叶片及真菌细胞跨膜的H+、K+、Ca2+和O2的振荡规律。通过对模型预测及实验测定数据的比较，用实验成功地证实了之前设想的正确性。 此项研究结合模型预测及实验数据，根据植物对盐、温度、渗透、低氧及pH胁迫的适应性反应，对振荡的生理学功能作了较为清晰的阐述。这个模型可以指导筛选抗盐、抗涝等方面的育种工作。

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Oscillations in plant membrane transport model predictions, experimental validation, and physiological implications

Abstract ：

Although oscillations in membrane-transport activity are ubiquitous in plants, the ionic mechanisms of ultradian oscillations in plant cells remain largely unknown, despite much phenomenological data. The physiological role of such oscillations is also the subject of much speculation. Over the last decade, much experimental evidence showing oscillations in net ion fluxes across the plasma membrane of plant cells has been accumulated using the non-invasive MIFE technique. In this study, a recently proposed feedback-controlled oscillatory model was used. The model adequately describes the observed ion flux oscillations within the minute range of periods and predicts: (i) strong dependence of the period of oscillations on the rate constants for the H⁺ pump; (ii) a substantial phase shift between oscillations in net H⁺ and K⁺ fluxes; (iii) cessation of oscillations when H⁺ pump activity is suppressed; (iv) the existence of some ‘window’ of external temperatures and ionic concentrations, where nondamped oscillations are observed: outside this range, even small changes in external parameters lead to progressive damping and aperiodic behaviour; (v) frequency encoding of environmental information by oscillatory patterns; and (vi) strong dependence of oscillatory characteristics on cell size. All these predictions were successfully confirmed by direct experimental observations, when net ion fluxes were measured from root and leaf tissues of various plant species, or from single cells. Because oscillatory behaviour is inherent in feedback control systems having phase shifts, it is argued from this model that suitable conditions will allow oscillations in any cell or tissue. The possible physiological role of such oscillations is discussed in the context of plant adaptive responses to salinity, temperature,osmotic, hypoxia, and pH stresses.