chapter1plantwatermetabolism【精選-ppt】(已修改)
2024-10-29 03:08 本頁面
【正文】 Chapter 1 Plant Water Metabolism ? Contents in brief: Absorption of water Transport of water Loss of water(transpiration) Irrigation 167。 1 水的結(jié)構(gòu)與特性 1. 結(jié)構(gòu)：水是極性分子，能形成分子間氫鍵 2. 水的特性 1) High boiling point(高沸點(diǎn) ) Compare: CH4 16 CH3CH3 30 CH3CH2CH3 44 CH3CH2CH2CH3 58 CH3(CH2)3CH3 72 boiling point 36℃ but : water 18 boiling point 100℃ reason: n H2O≒ (H2O) n +heat gas 2)Water has high specific heat(高比熱 ) ? The polarity of water and the resulting hydrogen bonding among water molecules means that it takes much heat (one calorie) to raise the temperature of 1 mL of water just 1176。 C. The hydrogen bonding has to be given a lot of energy to get them to vibrate and generate the temperature change. This property of water is called specific heat. It means that this liquid can absorb much heat from the various chemical reactions occurring in cells without temperature change。 it is a heat buffer. It helps maintain an even body temperature. 3) Water has a high latent heat of vaporization(高汽化熱 ) ? Among liquids, water has the highest latent heat of vaporization (44 kJmol1). This means that when water goes from liquid to gas it takes a lot of energy. This property can obviously be traced directly to hydrogen bonding again. As the highest energy molecules in the liquid achieve what it takes to move away as a gas, their energy is removed from the liquid and it gets cooler. We sometimes refer to this as evaporative cooling. This is a critical property in maintaining the temperature of dark green leaves essentially parked in sunshine. 3) Water demonstrates cohesion and adhesion(內(nèi)聚力和粘附力 ) ? 內(nèi)聚力 (Cohesion):液體狀況下同類分子間的吸引力叫內(nèi)聚力 ，水的內(nèi)聚力可達(dá) 30MPa. ? 粘附力 (adhesion):液相與固相間的吸引力叫粘附力或附著力 ? 原因：水是極性分子，與其它極性分子形成氫鍵。 ? 若水與某物質(zhì)的粘附力大于水的內(nèi)聚力，則水可吸附在該物質(zhì)上，該物質(zhì)即為可濕的，或可浸潤的；反之則不可濕或不可浸潤。如水可浸潤土壤 (SiO32)、濾紙、CO32， SO42等，而不可浸潤石碏，石墨等。 4) cohesion, adhesion and surface tension leads to capillarity(內(nèi)聚力、粘附力和表面張力導(dǎo)致毛細(xì)現(xiàn)象 ) h=2Tcos?/r?g= 106/r 毛細(xì)作用對植物的重要性 ： 1. 土壤下層的水分可通
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