低温逆境下冷敏果实机体传热特性与组织冷损伤相关性研究

Chilling injury of cold sensitive fruit originated permanent tissue injury caused by the heat lost of organism in low temperature stress. The thermal parameters played a very important role in low temperature stress reaction, which represented heat transfer capability and heat storage capacity of living tissues. In our previous study, it showed that there were obvious changes between the thermal parameters of cold sensitive fruit organism at different low temperature stress. To further explore the relationship of heat transfer performance and cold injury of cold sensitive fruit tissue in cold stress, the dynamic change rules of these thermal parameters were studied during chilling injury by the transient technique including of line heat resource and thermal pulse-decay and differential scanning calorimetry. The potential mechanism for response of heat transfer performance in low temperature stress was explored. The effect of physiological structures changes especially electrolyte leakage from cell membrane permeability increasing and intercellular space enlarging on heat transfer performance was illuminated. The model was built for predicting of chilling injury of cold sensitive fruit in low temperature stress. The data of prediction and control of chilling injury was obtained. This work are significant to theoretical research of the relationship of heat transfer performance and cold injury of cold sensitive fruit tissue, but it provides new models of thinking to reveal adversity plant life law as well. All these make it possible for the present phenomenological plant life science to be quantified.

冷敏果实冷害起源于低温逆境引起的机体热量散失导致的生物组织永久性损伤，在低温逆境反应中，揭示生物活体热量传输能力和载热能力的热特性参数具有重要作用。我们前期研究表明，不同低温逆境条件下冷敏果实机体热特性参数具有较明显的变化。为进一步探索低温逆境下果实机体传热特性与其组织冷损伤之间的相关性，本项目拟通过线热源瞬态技术、热脉冲衰减技术、差示扫描量热技术等对冷敏果实机体热特性参数在冷害发生过程中的动态变化规律进行研究，探索冷敏果实机体传热特性在低温逆境下的响应机制，阐明冷损伤组织生理结构尤其是细胞膜透性增加引起的电解质外渗和细胞间隙变化等对其传热特性的影响，建立低温逆境下冷敏果实冷害预示模型，得到冷害预示和控制的基础研究数据。研究结果不仅对冷敏果实机体传热特性与其组织冷损伤相关性研究具有重要的理论意义，而且还将为植物逆境生命规律揭示提供新的模式和思路，使现今唯象的植物生命科学走向定量化成为可能。

低温逆境造成的植物冷害严重威胁着农作物的生长发育和采后农产品的贮藏保鲜，冷害是我国乃至世界果蔬生长发育和采后农产品的贮藏保鲜面临的一大课题。本项目在已有研究成果基础上，以冷敏型果实黄瓜、西葫芦、茄子等为试材，从热物理学的角度出发，研究了冷敏果实机体传热特性在冷害过程中的动态变化规律及逆境响应机制，并结合低温逆境胁迫条件下的冷敏果实的生理生化指标测试，分析探讨果实传热特性与组织冷害生理结构尤其是细胞膜透性增加引起的电解质外渗和细胞间隙变化等的相关关系；结果表明：低温逆境胁迫条件下，冷敏果实POD、SOD、CAT等酶活性受到抑制，无法协同清理冷敏果实组织内的自由基，导致MDA含量大量累积，膜渗透性增大，细胞间隙增大，组织热传递能力减小，从传热学角度分析，这可能与细胞间隙中充满了热导率小且不流动的空气以及组织细胞膜由液晶态向凝胶态转变有关，继而使生物组织抵御外界低温，减小自身机体热量流失，这可能是生物组织对低温逆境的一种自身保护性反应；而当果实从低温条件下取出后，组织热导率又出现增大趋势，这可能是由于细胞膜损伤程度加重，膜透性增大，电解质大量渗出使果肉组织密度增大所致；冷敏果实热导率、热扩散率随贮藏时间延长有较为一致的变化趋势，冰点呈现上升趋势；热焓及比热容等参数变化不大；依据传热学理论，通过监测组织样品降温动力学曲线过程中上下表面温差的差异评价低温逆境下冷敏果实组织冷损伤度并建立了相应的测试装置；结合二次回归正交旋转组合设计确定黄瓜果实低温冷害临界值，建立低温逆境下未成熟期和成熟期黄瓜果实冷害预示模型。研究成果为冷敏果实冷害机理的研究以及冷害预示和控制提供了一定的理论和基础研究依据，进一步可为逆境植物生命规律的揭示和解决提供新的模式和探索。