植物膜轉(zhuǎn)運(yùn)的模型預(yù)測、實(shí)驗(yàn)驗(yàn)證及生理學(xué)影響

細(xì)胞膜是控制細(xì)胞振蕩的中心，細(xì)胞的振蕩在植物界中十分普遍。例如質(zhì)膜電位的周期性變化、液泡電位及電流的波動(dòng)、質(zhì)外體的濃度變化、胞內(nèi)pH及Ca2+的波動(dòng)、不同細(xì)胞類型質(zhì)膜跨膜離子流振蕩等。然而，目前除了大致了解膜和離子流直接或間接參與振蕩過程，研究人員對這種振蕩的生理學(xué)功能仍然知之甚少。 Shabala等研究人員應(yīng)用反饋受控振蕩模型提出了許多設(shè)想：（1）振蕩周期強(qiáng)烈依賴于質(zhì)子泵活性；（2）質(zhì)子泵活性受抑制時(shí)，振蕩停止；（3）H+和K+流之間存在方向性的轉(zhuǎn)變；（4）細(xì)胞膜上有對外界溫度和離子濃度變化感受的“窗口”，對外界不同的變化細(xì)胞表現(xiàn)為不同的振蕩模式；（5）振蕩特性與細(xì)胞大小緊密相關(guān)等。他們使用“非損傷微測技術(shù)”直接測定了不同環(huán)境條件下植物根、葉片及真菌細(xì)胞跨膜的H+、K+、Ca2+和O2的振蕩規(guī)律。通過對模型預(yù)測及實(shí)驗(yàn)測定數(shù)據(jù)的比較，用實(shí)驗(yàn)成功地證實(shí)了之前設(shè)想的正確性。 此項(xiàng)研究結(jié)合模型預(yù)測及實(shí)驗(yàn)數(shù)據(jù)，根據(jù)植物對鹽、溫度、滲透、低氧及pH脅迫的適應(yīng)性反應(yīng)，對振蕩的生理學(xué)功能作了較為清晰的闡述。這個(gè)模型可以指導(dǎo)篩選抗鹽、抗?jié)车确矫娴挠�種工作。

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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.