沈阳市东陵区景观生态潜力研究

沈阳市东陵区景观生态潜力研究赵羿,吴彦明（中国科学院沈阳应用生态研究所,１１００１５）邓百祥（辽宁省水利水电勘测设计研究院,沈阳１１０００６）ＥｃｏｌｏｇｉｃａｌＰｏｔｅｎｔｉａｌｏｆＬａｕｄｓｃａｐｅｉｎＤｏｎｇｌｉｎｇＤｉｓｔｒｉｃｔｏｆＳｈｅｎｙａｎｇ￥ＺｈａｏＹｉ;ＷｕＹａｎｍｉｎｇ（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＥｃｏｌｏｇｙ,ＡｃａｄｅｍｉａＳｉｎｉｃａ,Ｓｈｅｎｙａｎｇ１１００１５）,ＤｅｎｇＢａｉｘｉａｎｇ（ＬｉａｏｎｉｎｇＡｃａｄｅｍｙｏｆＷａｔｅｒＣｏｎ－ｓｅｒｖａｎｃｙａｎｄＷａｔｅｒＰｏｗｅｒＳｕｒｅｅｙｉｎｇａｎｄＤｅｓｉｇｎｉｎｇ,Ｓｈｅｎｙａｎｇ１１０００６）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（５）：１－８。Ｅｃｏｌｏｇｉｃａｌｐｏｔｅｎｔｉａｌｏｆｌａｕｄｓｃａｐｅｃｏｎｓｉｓｔｓｏｆｉｔｓｐｒｏｄｕｃｔｉｖｅｐｏｔｅｎｔｉａｌ,ｅｃｏｌｏｇｉｃａｌｐｏｔｅｎｔｉａｌａｎｄｐｒｉｃｅｌｅｓｓｐｏ－ｔｅｎｔｉａｌ．Ｔｈｒｏｕｇｈｃａｌｃｕｌａｔｉｎｇｄｉｆｆｅｒｅｎｔｐｒｏｄｕｃｔｉｖｅｐｏｔｅｎｔｉａｌｓ（ｐｈｏｔｏｓｙｎｔｈｅｔｉｃｐｏｔ     

Brine Shrimp致死率生物鉴定法对八种民间药活性成分的研究

采用ＴｈｅＢｒｉｎｅＳｈｒｉｍｐＬｃｔａｌｉｔｙＢｉｏａｓｓａｙ法对民间药翼蓼ＰｔｅｒｏｘｙｇｏｎｕｍｇｉｒａｌｄｉｉＤｕｍｍｅｒｅｔＤｉｅｌｓ）,金荞麦（Ｆａｇｏｐｙｒｕｍｄｉｂｏｔｒｙｓ（Ｄ．Ｄｏｎ）Ｈａｒａ）,齿果酸模（ＲｕｍｅｘｄｅｎｔａｔｕｓＬ．）巴天酸模（ＲｕｍｅｘｐａｔｉｅｎｔｉａＬ．）网果酸模（ＲｕｍｅｘｄｉｃｔｙｏｃａｒｐｕｓＢｏｉｓｓｅｔＢｕｈｓｅ）、掌叶大黄（Ｒｈｅｕｍｐａｌ     

多荚草中的新三萜皂甙

从石竹科植物多荚草（Ｐｏｌｙｃａｒｐｏｎ ｐｒｏｓｔｒａｔｕｍ（Ｆｏｒｓｓｋ．）Ａｓｃｈｅｒｓ．ｅｔ Ｓｃｈｗｅｉｎ．ｅｘ Ａｓｃｈｅｒｓ）中分离得到３个新的柴胡皂甙类化合物：ｐｒｏｓｔｒａｔｏｓｉｄｅ Ａ￣Ｃ（１￣３）。它们的结构通过波谱方法分别鉴定为：３－Ｏ－｛β－Ｄ－ｘｙｌｏｐｙｒａｎｏｓｙｌ－（１→２）－β－Ｄ－ｇｌｕｃｏｐｙｒａｎｏｓｙｌ－（１→４）－「β－Ｄ－ｇｌｕｃｏｐｙｒａｎｏｓｙ     

普通小麦基因组最可能的4个供体的ITS1和ITS2序列及其亲缘关系

对普通小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）基因组（ＡＡＢＢＤＤ）最可能的供体－Ｔ．ｕｒａｔｒｔｕＴｈｕｍ．（ＡＡ）、Ｔ．ｍｏｎｏｃｃｕｍｖａｒ．ｂｏｅｏｔｉｃｕｍ（Ｂｏｉｓｓ．）ＭＫ（ＡＡ）、ＡｅｇｉｌｏｐｓｓｐｅｌｔｏｉｄｅｓＴａｕｓｃｈ．和Ａｅ．ｔａｕｓｃｈｉｉ（Ｃｏｓｓ．（ＤＤ）的核糖体ＲＮＡ基因ＩＴＳ区进行了ＰＣＲ扩增和克隆,并测定了ＩＴＳ１和ＩＴＳ２的ＤＮＡ序列,讨论和纠正了前人     

薯蓣皂甙元分离工艺的研究及其综合利用

采用“分离法加工薯蓣植物”的工艺技术是将薯蓣根茎带水磨碎,在水中筛分,将各有用成分分开后,分别采用适宜的方法加工利用。本文报道利用薯蓣植物盾叶薯蓣（ＤｉｏｓｃｏｒｅａｚｉｎｇｉｂｅｒｅｎｓｉｓＣ．Ｈ．Ｗｒｉｇｈｔ）和穿龙薯蓣（ＤｉｏｓｃｏｒｅａｎｉｐｐｏｎｉｃａＭａｋｉｎｏ）制取薯蓣皂甙元（Ｄｉｏｓｇｅｎｉｎ）和药用酵母粉（Ｓａｃｃｈａｒｏｍｙｃｅｓｓｉｃｃｕｍ）的方法。     

沈阳市东陵区丘陵坡地坡面太阳直射光的分布及其分析

沈阳市东陵区丘陵坡地坡面太阳直射光的分布及其分析郭林海（中国科学院沈阳应用生态研究所,１１００１５）ＤｉｓｔｒｉｂｕｔｉｏｎｏｆＤｉｒｅｃｔＳｏｌａｒＲａｄｉａｔｉｏｎｏｎＨｉｌｌｙＳｌｏｐｅｓｏｆＤｏｎｇｌｉｎｇＤｉｓｔｒｉｃｔｏｆＳｈｅｎｙａｎｇＭｕｎｉｃｉｐａｌｉｔｙａｎｄＩｔｓＡｎａｌｙｓｉｓ￥ＧｕｏＬｉｎｈａｉ（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＥｃｏｌｏｇｙ,ＡｃａｄｅｍｉａＳｉｎｉｃａ,Ｓｈｅｎｙａｎｇ１１００１５）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（１）：５９－６１．Ｂａｓｅｄｏｎｔｈｅｌａｔｅｓｔ１：５００００ｔｏｐｏｇｒａｐｈｉｃｍａｐ,ｔｈｅ１：１０００００ｓｌｏｐｅｇｒａｄａｔｉｏｎｍａｐｉｓｄｒａｗｎｏｕｔａｎｄａｒｅａｃａｌｃｕｌａｔｉｏｎｉｓｍａｄｅ．Ｔｈｅｄｉｒｅｃｔｓｏｌａｒｒａｄｉａｔｉｏｎｉｎｔｙｐｉｃａｌｓｉｔｅｓｏｆｔｈｅｄｉｓｔｒｉｃｔｉｓｍｅａｓｕｒｅｄａｎｄｃａｌｃｕｌａｔｅｄ,ａｎｄｔｈｅｖａｒｉａｔｉｏｎｃｕｒｖｅｓｏｆａｎｎｕａｌｆｌｕｘｏｆｄｉｒｅｃｔｓｏｌａｒｒａｄｉａｔｉｏｎｏｎｖａｒｉｏｕｓｓｌｏｐｅｄｉｒｅｃｔｉ     

大连潮间带底栖海藻群落的数量特征和优势种的季节变化

大连潮间带底栖海藻群落的数量特征和优势种的季节变化熊韶峻,王献平,郭旭光（辽宁师范大学生物系,大连１１６０２２）ＳｅａｓｏｎａｌＶａｒｉａｔｉｏｎｏｆＱｕａｎｔｉｔａｔｉｖｅＣｈａｒａｃｔｅｒｓａｎｄＤｏｍｉｎａｎｔＳｐｅｃｉｅｓｏｆＢｅｎｔｈｉｃＳｅａｗｅｅｄＣｏｍｍｕｎｉｔｉｅｓｗｉｔｈｉｎＩｎｔｅｒｔｉｄａｌｓｉｎＤａｌｉａｎ,Ｃｈｉｎａ￥．ＸｉｏｎｇＳｈａｏｊｕｎ,ＷａｎｇＸｉａｎｐｉｎｇ,ＧｕｏＸｕｇｕａｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＢｉｏｌｏ－ｇｙ,ＬｉａｏｎｉｎｇＮｏｒｍａｌＵｎｉｕｅｒｓｉｔｙ,Ｄａｌｉａｎ１１６０２２）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（４）：２７－２９．Ｔｈｅｃｏｍｐｏｓｉｔｉｏｎ,ｃｏｖｅｒａｇｅ,ｂｉｏｒｎａｓｓａｎｄｄｏｒｎｉｎａｎｔｓｐｅｃｉｅｓｏｆｂｅｎｔｈｉｃｓｅａｗｅｅｄｃｏｒｎｍｕｎｌｔｙｗｉｔｈｉｎｉｎｔｅｒｔｉｄａｌｉｎＤａｌｉａｎ,ＣｈｉｎａｗｅｒｅｍｏｎｔｈｌｙｉｎｖｅｓｔｉｇａｔｅｄｆｒｏｒｎＭａｒｃｈ１９９０ｔｏＭａｒｃｈ１９９１．Ｉｔｉｓｘｈｏｗｎｔｈａｔ１）．ｔｈｅｇｅｎ－ｅｒａｌｔｅｎｄｅｎｃｙｏｆｓｅａｓｏ     

氮磷钾肥施用对蔬菜中硝酸盐积累的数学模型

氮磷钾肥施用对蔬菜中硝酸盐积累的数学模型段咏新付庭治（徐州师范学院生物系,２２１００９）（南京大学生物系,２１０００８）ＭａｔｈｅｍａｔｉｃａｌＭｏｄｅｌｏｎＮｉｔｒａｔｅＡｃｃｕｍｕｌａｔｉｏｎｉｎＶｅｇｅｔａｂｌｅａｆｔｅｒＡｐｐｌｙｉｎｇＮ,ＰａｎｄＫＦｅｒｔｉｌｉｚｅｒｓ￥ＤｕａｎＹｏｎｇｘｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＢｉｏｌｏｇｙ,ＸｕｚｈｏｕＴｅａｃｈｅｒ＇ｓＣｏｌｌｅｇｅ,２２１００９）,ＦｕＴｉｎｇｚｈｉ（ＤｅｐａｒｔｍｅｎｔｏｆＢｉｏｌｏｇｙ,ＮａｎｊｉｎｇＵｎｉｖｅｒｓｉｔｙ,２１０００８）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（６）：３４－３６．ＩｎＴｈｉｓｐａｐｅｒ,ａｒｅｇｒｅｓｓｉｏｎｗｏｄｅｌｏｎｎｉｔｒａｔｅａｃｃｕｍｕｌａｔｉｏｎｉｎｓｐｉｒａｃｈｉｓｅｓｔａｂｌｉｓｅｄ,ｗｈｉｃｈｃａｎｐｒｅｄｉｃｔｔｈｅａｃｃｕｍｕｌａｔｉｏｎａｍｏｕｎｔｏｆｎｉｔｒａｔｅｕｎｄｅｒｄｉｆｆｅｒｅｎｔａｐｐｌｉｃａｔｉｏｎｒａｔｅｓｏｆＮ,ＰａｎｄＫｆｅｒｔｉｌｉｚｅｒｓ。Ｕｓｉｎｇｔｈｉｓｍｏｄｅｌ,ｔｈｅｎｉｔｒａｔｅｃｏｎｔｅｎｔｉｎｓｐｉｒａｃｈｃａ     

关于灌木生物量建模方法的改进

关于灌木生物量建模方法的改进张峰,上官铁梁李素珍（山西大学生物系,太原０３０００６）（太原治金工业学校,０３０００２）ＩｍｐｒｏｖｅｍｅｎｔｏｎｔｈｅＭｏｄｅｌｌｉｎｇＭｅｔｈｏｄｏｆＢｉｏｌｍａｓｓｏｆＢｒｕｓｈ￥ＺｈａｎｇＦｅｎｇ;ＳｈａｎｇｇｕａｎＴｉｅｌｉａｎｇ（Ｄｅｐａｒｔ－ｍｅｎｔｏｆＢｉｏｌｏｇｙ,ＳｈａｎｘｉＵｎｉｖｅｒｓｉｔｙ,Ｔａｉｙｕａｎ０３０００６）,ＬｉＳｕｚｈｅｎ（ＴａｉｙｉｉａｎＭｅｔａｌｌｉｔｒｇｉｃａｌＳｃｈｏｏｌ,Ｔａｉｙｕａｎ０３０００２）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＶＥｃｏｌｏｇｙ,１９９３,１２（６）：６７－６９．ＤｕｒｉｎｇｍａｋｉｎｇｒｅｓｅａｒｃｈｏｎｔｈｅｂｉｏｍａｓｓｏｆＥｌａｅａｇｎｕｓｍｏｌｌｉｓ,ｔｈｅｒｅｇｒｅｓｓｉｏｎｍｏｄｅｌｏｆｔｈｅｂｉｏｍａｓｓｉｓｂｕｉｌｔｂｙｒｅｐｌａｃｉｎｇＤ￣２ＨｗｉｔｈＣＨ,Ｔｈｅｒｅｓｕｌｔｓｈｏｗｓｔｈａｔｎｏｔｏｎｌｙｉｔｉｓｃｏｎｖｉｎｉｅｎｔｉｎｔｈｅｆｉｅｌｄｗｏｒｋ,ｂｕｔａｌｓｏｔｈｅｆｏｒｅｃａｓｔｍｏｄｅｌｈａｓｍｏｒｅＤｒｅｃｉｓｉｏｎｗｈｅｎＣＨｉｓｕｓｅｄａｓｔｈｅｉｎｄｅｐｅｎｄ     

我国南海海龟资源的调查与保护研究现状与展望

我国南海海龟资源的调查与保护研究现状与展望王亚民（中华人民共和国农业部水产司,北京１０００２６）ＡｃｈｉｅｖｅｍｅｎｔａｎｄＰｅｒｓｐｅｃｔｉｖｅｏｆｔｈｅＲｅｓｅａｒｃｈｅｓｏｎＳｏｕｔｂＣｈｉｎａＳｅａＴｕｒｔｌｅＲｅｓｏｕｒｃｅｓａｎｄＰｒｏｔｅｃｔｉｏｎｉｎＣｂｉｎａ￥ＷａｎｇＹａｍｉｎ（ＤｉｖｉｓｉｏｎｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙ,ＤｅｐａｒｔｍｅｎｔｏｆＦｉｓｈｅｒｙ,Ｐｅｏｐｌｅ’ｓＲｅｐｕｂｌｉｃｏｆＣｈｉｎａＭｉｎｉｓｔｒｙｏｆＡｇｒｉｃｕｌｔｕｒｅ,Ｂｅｉｊｉｎｇ１０００２６）．ＣｈｉｎｅｓｅＪｏｕｒｎａｌｏｆＥｃｏｌｏｇｙ,１９９３,１２（６）：６０－６１．ＴｈｉｓｐａｐｅｒｉｎｔｒｏｄｕｃｅｓｔｈｅｒｅｓｅａｒｃｈｅｓｉｎｆｉｅｌｄｏｆＳｏｕｔｈＣｈｉｎａＳｅａｔｕｒｔｌｅｒｅｓｏｕｒｃｅｓａｎｄｐｒｏｔｅｃｔｉｏｎｉｎＣｈｉｎａ．ＴｈｅｒｅａｒｅｆｉｖｅｓｐｅｃｉｅｓｓｅａｔｕｒｔｌｅｓｉｎＣｈｉｎａ,ａｂｏｕｔ９０％ｏｆｔｈｅｍｌｉｖｅｉｎＳｏｕｔｈＣｈｉｎａｓｅａ。Ｄｕｒｉｎｇ１９５９－１９８８,３１８４．Ｉｔｓｅａｔｕｒｔｌｅｗｅｒｅｃａｔｃｈｅｄ（ａｂｏｕｔ     

Response of wheat canopy CO2 and water gas-exchange to soil water content under ambient and elevated CO2

The nature of the interaction between drought and elevated CO₂ partial pressure (pC_a) is critically important for the effects of global change on crops. Some crop models assume that the relative responses of transpiration and photosynthesis to soil water deficit are unaltered by elevated pC_a, while others predict decreased sensitivity to drought at elevated pC_a. These assumptions were tested by measuring canopy photosynthesis and transpiration in spring wheat (cv. Minaret) stands grown in boxes with 100 L rooting volume. Plants were grown under controlled environments with constant light (300 µmol m^?2 s^?1) at ambient (36 Pa) or elevated (68 Pa) pC_a and were well watered throughout growth or had a controlled decline in soil water starting at ear emergence. Drought decreased final aboveground biomass (?15%) and grain yield (?19%) while elevated pC_a increased biomass (+24%) and grain yield (+29%) and there was no significant interaction. Elevated pC_a increased canopy photosynthesis by 15% on average for both water regimes and increased dark respiration per unit ground area in well‐watered plants, but not drought‐grown ones. Canopy transpiration and photosynthesis were decreased in drought‐grown plants relative to well‐watered plants after about 20–25 days from the start of the drought. Elevated pC_a decreased transpiration only slightly during drought, but canopy photosynthesis continued to be stimulated so that net growth per unit water transpired increased by 21%. The effect of drought on canopy photosynthesis was not the consequence of a loss of photosynthetic capacity initially, as photosynthesis continued to be stimulated proportionately by a fixed increase in irradiance. Drought began to decrease canopy transpiration below a relative plant‐available soil water content of 0.6 and canopy photosynthesis and growth below 0.4. The shape of these responses were unaffected by pC_a, supporting the simple assumption used in some models that they are independent of pC_a.     

丛枝菌根真菌对杨树生长、气孔和木质部微观结构的影响

植物气孔与木质部导管及纤维的功能直接关系着植物的水分利用, 进而影响植物的生长。为研究丛枝菌根真菌(AMF)对杨树抗旱性的影响, 采用温室盆栽的方法, 研究两种水分条件下, 接种根内球囊霉(Rhizophagus irregularis)对速生杨107 Populus × canadensis (P. nigra × P. deltoides) ‘Neva’气孔及木质部微观结构的影响。结果表明: AMF的侵染显著提高了杨树幼苗地上和地下部分生物量, 对叶片气孔长度、茎部导管细胞直径和纤维细胞长度也有促进作用。AMF对生物量和导管细胞直径的增加幅度表现出干旱条件下>正常水分条件下, 而对气孔长度的提高幅度表现出干旱条件下<正常水分条件下。正常水分条件下, AMF增加了杨树叶片的气孔密度, 减小了纤维细胞直径, 对相对水分饱和亏缺无影响; 干旱条件下, AMF增加了纤维细胞直径, 降低了相对水分饱和亏缺, 对气孔密度无影响。综上所述, 干旱条件下, AMF对导管水分传输能力的促进作用明显增加, 而对气孔蒸腾能力的促进作用有所减少, 从而更利于杨树在遭遇干旱时保持水分, 减少干旱对菌根杨树造成的水分亏缺, 提高菌根杨树对干旱的耐受性。     

Physiological, stomatal and ultrastructural ozone responses in birch (Betula pendula Roth.) are modified by water stress

The physiological, stomatal and ultrastructural responses to ozone and drought of ozone-sensitive and more ozone-tolerant birch ( Betula pendula Roth.) clones were studied singly and in combination, in a high-stress chamber experiment and in a low-stress open-field experiment. In the chamber experiment, well watered (WW), moderately watered (MW) or drought-stressed (DS) saplings were exposed for 36 d to 0 or 130 nmol mol^∠1 ozone. In the open-field experiment, well watered or drought-stressed saplings were grown for one growing season in ambient air or exposed to 1·8 × ambient ozone. Drought stress reduced growth rate, stomatal conductance, stomatal density and the proportion of starch and thylakoids in chloroplasts, but stimulated net photosynthesis, Rubisco and chlorophyll quantity at the end of the growing season, and increased the size and density of plastoglobuli. Ozone fumigations caused more variable, clone- and exposure-dependent responses in growth, decreased stomatal conductance and net photosynthesis, an increased number of stomata, visible and ultrastructural chloroplast injuries, and enhanced autumn yellowing of the leaves. Ozone-induced changes in plastoglobuli, starch and thylakoids resembled drought responses. The two experiments revealed that, depending on the experimental conditions and the variable, the response to drought and ozone stress can be independent, additive or interactive. Drought protected the plants from ozone injuries under high-stress conditions in the chamber experiment. In the low-stress, open-field experiment, however, enhanced ozone damage was observed in birch saplings grown under restricted water supply.     

Stomatal responses to long-term high vapor pressure deficits mediated most limitation of photosynthesis in tomatoes

Plants grown at high vapor pressure deficit (VPD) usually present decreased photosynthesis, but stomatal and mesophyll limitation to photosynthesis remain poorly quantified. To better understand the regulation of high VPD on photosynthesis and plant growth in tomatoes, we investigated the limitation of stomatal conductance and mesophyll conductance to photosynthesis and relative importance of stomatal morphology and function in stomatal conductance. Both the net photosynthesis rate and total biomass were significantly limited by high VPD. Meanwhile, stomatal conductance and mesophyll conductance were decreased under high VPD. The stomatal conductance limitation was responsible for 60% of the total photosynthetic limitation. Moreover, a reduction in stomatal density and stomatal size occurred under high VPD, which was significantly correlated with the down-regulation of stomatal conductance. The stomatal morphology contributed to more than half the change in stomatal conductance. Nevertheless, stomatal movement was also an important factor in regulating stomatal conductance. The decrease of hydraulic conductance and transpiration rate with no significant difference in relative water content, leaf water potential, and/or osmotic potential suggested passive hydraulic regulation in the feedforward responses of stomata to high VPD.     

Gas exchange in paphiopedilum: lack of chloroplasts in guard cells correlates with low stomatal conductance

Net photosynthesis and stomatal conductance were measured in attached leaves of Paphiopedilum insigne. At 20°C and a vapor-pressure deficit of 0.5 kilopascal, both net photosynthesis and stomatal conductance were light-saturated below 0.2 millimole per square meter per second, a response typical of shade plants. The absolute values of photosynthetic rate and conductance however were remarkably low, presumably reflecting an adaptation to the low-light, limited-nutrient habitat characteristic of these orchids. The leaves also showed a vapor-pressure deficit response, with net photosynthesis and conductance varying over a 2-fold range between 0.3 and 1.6 kilopascals.

These results confirm that Paphiopedilum stomata are functional. The correlation between achlorophyllous guard cells and low conductance rates, however, singles them out as an exceptional biological system, exhibiting basic differences from typical stomata in higher plants. Available evidence showing that guard-cell chloroplasts are needed to sustain high conductance rates at moderate to high irradiances indicates that the genetic changes leading to the loss of chloroplast differentiation in Paphiopedilum guard cells were not deleterious because of the low conductance rates characteristic of this genus.

     

Effect of leaf water deficit on stomatal and nonstomatal regulation of net carbon dioxide assimilation

The effect of leaf water deficit on net CO₂ assimilation was studied under two conditions: in one, the stomata were allowed to contribute to the regulation of CO₂ assimilation; in the other, air was forced through the leaf at a constant rate to overcome the effects of change in stomatal resistance accompanying changes in leaf water deficit. When the stomata were allowed to regulate the gaseous diffusive resistance of the leaf, CO₂ assimilation decreased with increasing leaf water deficit. However, when air was forced through the leaf, the rate of assimilation was not inhibited by increasing leaf water deficit. The results indicate that the inhibition of net CO₂ assimilation with increasing leaf water deficit is a consequence of an increase in the diffusive resistance to gas exchange and not of a change in apparent mesophyll resistance.     

Behavior of Corn and Sorghum under Water Stress and during Recovery

Corn (Zea mays L.) and sorghum (Sorghum vulgare, Pers.) plants were grown in a vermiculite-gravel mixture in controlled environment chambers until they were 40 days old. Water was withheld until they were severely wilted, and they were then rewatered. During drying and after rewatering stomatal resistance was measured with a diffusion porometer each morning, and water saturation deficit and water potential were measured on leaf samples. The average resistance of the lower epidermis of well watered plants was lower for corn than for sorghum. When water stress developed, the stomata began to close at a higher water potential in corn than in sorghum. The stomata of both species began to reopen normally soon after the wilted plants were rewatered, and on the 2nd day the leaf resistances were nearly as low as those of the controls. The average leaf water potential of well watered corn was −4.5 bars; that of sorghum, −6.4 bars. The lowest leaf water potential in stressed corn was −12.8 bars at a water saturation deficit of 45%. The lowest leaf water potential in stressed sorghum was −15.7 bars, but the water saturation deficit was only 29%. At these values the leaves of both species were tightly rolled or folded and some injury was apparent. Thus, although the average leaf resistance of corn is little lower than that of sorghum, corn loses much more of its water before the stomata are fully closed than does sorghum. The smaller reduction in water content of sorghum for a given reduction in leaf water potential is characteristic of drought-resistant species.     

Polyploids and their structural and PHYSIOLOGICAL CHARACTERISTICS RELATIVE TO WATER DEFICIT IN BETULA PAPYRIFERA (Betulaceae)

The morphology and leaf anatomy, water relations, gas exchange, and growth characteristics of Betula papyrifera seedlings grown in a greenhouse representing three ploidy levels (diploids, pentaploids, and hexaploids) have been compared in an effort to understand the role of polyploidy in habitat differentiation and adaptation to water deficit. The polyploids are more tolerant of water deficit than their diploid relatives. The polyploids have fewer stomata per unit area and smaller stomatal indices than the diploids. They also have thicker upper and lower epidermis and more pubescence, which tend to reduce water loss. The polyploids have lower osmotic potential at saturation (_p.sat) than corresponding diploids, suggesting they are more able to maintain turgor in the case of low tissue water potential than the diploids. The photosynthesis of the diploids is more sensitive to water deficit. A 2-hr artificial water stress treatment caused complete cessation of photosynthesis in the diploids. They are more drought-avoiding than the polyploids as evidenced by closing their stomata to limit water loss at a relatively higher tissue water potential (-1.425 MPa). The pentaploids and hexaploids maintained, although to a small extent, photosynthesis when their tissue water potentials dropped to -1.86 MPa and -2.07 MPa, respectively.     

夏玉米叶片水分变化与光合作用和土壤水分的关系

叶片是光合作用的重要器官,其含水量的变化必将影响光合作用,但关于叶片水分变化对光合作用的影响报道较少。以华北夏玉米为研究对象,利用三叶期不同水分梯度的持续干旱模拟试验资料,分析夏玉米叶片水分变化及其与叶片净光合速率和土壤水分的关系。结果表明:夏玉米叶片净光合速率对叶片水分变化的响应显著且呈二次曲线关系,叶片含水量约为70.30%时,叶片净光合速率为零;叶片含水量与土壤相对湿度呈非直角双曲线关系,叶片最大含水量约为85.14%。研究结果可为准确描述叶片水分变化对光合作用的影响及客观辨识夏玉米干旱的发生发展及监测预警提供参考。     

The effect of water stress on photosynthetic carbon metabolism in four species grown under field conditions

Abstract. The effect of gradually-developing water-stress has been studied in Lupinus albus L., Helianthus annuus L., Vitis vinifera cv. Rosaki and Eucalyptus globulus Labill. Water was withheld and diurnal rhythms were investigated 4–8d later, when the predawn water deficit was more negative than in watered plants, and the stomata closed almost completely early during the photoperiod. The contribution of ‘stomatal’ and ‘non-stomatal’ components to the decrease of photosynthetic rate was investigated by (1) comparing the changes of the rate of photosynthesis in air with the changes of stomatal conductance and (2) measuring photosynthetic capacity in saturating irradiance and 15% CO₂. Three species (lupin, eucalyptus and sunflower) showed larger changes of stomatal conductance than photosynthesis in air, and showed little or no decrease of photosynthetic capacity in saturating CO₂. Photosynthesis in air also recovered fully overnight after watering the plants in the evening. In grapevines, stomatal conductance and photosynthesis in air changed in parallel, there was a marked decrease of photosynthetic capacity, and photosynthesis and stomatal conductance did not recover overnight after watering water-stressed plants. Relative water content remained above 90% in grapevine. We conclude that non-stomatal components do not play a significant role in lupins, sunflower or eucalyptus, but could in grapevine. The effect of water-stress on partitioning of photosynthate was investigated by measuring the amounts of sucrose and starch in leaves during a diurnal rhythm, and by measuring the partitioning of ¹⁴C-carbon dioxide between sucrose and starch. In all four species, starch was depleted in water-stressed leaves but sucrose was maintained at amounts similar to, or higher than, those in watered plants. Partitioning into sucrose was increased in lupins and eucalyptus, and remained unchanged in grapevine and sunflower. It is concluded that water-stressed leaves in all four species maintain high levels of soluble sugars in their leaves, despite having lower rates of field photosynthesis, decreased rates of export, and low amounts of starch in their leaves.