RELATION BETWEEN POSITIVE TO NEGATIVE PHOTOTROPIC INVERSION AND TURGOR REGULATIVE FUNCTION IN VAUCHERIA.

摘要研究了淡水种陆生水蚤（VAUCHERIA v.s terrestris， VT）和咸淡水种双角水蚤（VAUCHERIA dihotoma， VD）的趋光反应调控与膨体调节能力之间的关系。VT耐盐性低，对强度大于50Wm^<-2>的白光表现出负向光性，而VD即使在海水中也能生存，对太阳直射光表现出正向光性。钙的加入大大提高了VT和VD的耐盐性。在高渗透压培养基中培养时，两种植物生长的细胞顶端直径减小。渗透压相同且大于50mOsm的NaCl和山梨醇诱导VT的负向光性；另一方面，VD的反应只能由山梨醇引起，而不能由相同渗透压的NaCl引起。这表明趋光反转和根尖收缩与低膨压独立相关。为了比较和分析vt和vd的膨润调节能力，采用新改进的离子色谱系统测定了细胞离子组成。在5mM Ca存在下，在蓝光下，VT主要吸收Na^+和Cl^-，从而恢复其原有的膨胀。然而，在山梨醇培养基中，VT作为一种钠植物，由于缺乏钠而不能调节膨润。在白光条件下（12l / 12d）， vt部分失去调节膨胀的能力，而vd没有。VD被认为是一种钾植物，它吸收大量的K^+、Na^+、Cl^-和SO_4^<2->来调节其膨胀。在高达400mOsm的外部渗透压下具有膨胀性。本研究结果强烈提示，虚菌的负向光性表达与胀气调节失败或持续的低胀压有关。低膨感与负向光性表达之间的潜在机制有待进一步研究。

RELATION BETWEEN THE REGULATION OF PHOTOTROPIC RESPONSE AND ABILITY OF TURGOR REGULATION IN TWO, VAUCHERIA SPECIES,A FRESH WATER SPECIES V.terrestris (VT) AND BRACKISH WATER SPECIES V.dichotoma (VD) WAS INVESTIGATED.VT HAS LOW SALINITY TOLERANCE,AND EXHIBITS NEGATIVE PHOTOTROPISM TO WHITE LIGHT OF THE INTENSITY HIGHER THAN 50Wm^<-2>, WHILE VD CAN SURVIVE EVEN IN SEA WATER AND SHOWS POSITIVE PHOTOTROPIC RESPONSE TO DIRECT SUN LIGHT.ADDITION OF Ca VERY MUCH IMPROVES SALT TOLERANCE IN BOTH VT AND VD.DIAMETER IN GROWING CELL APICES OF THE TWO SPECIES DECREASES WHEN THEY ARE CULTURED IN MEDIA OF HIGH OSMOLARITY.NEGATIVE PHOTOTROPISM OF VT IS INDUCED BY NaCl AND SORBITOL OF THE SAME OSMOLARITY,HIGHER THAN 50mOsm ; THAT OF VD IS,ON THE OTHER HAND,INDUCED ONLY BY SORBITOL,NOT BY NaCl OF THE SAME OSMOLARITY.THIS INDICATES THAT PHOTOTROPIC INVERSITION AND APICAL CONTRACTION ARE INDEPENDENTLY CORRELATING WITH LOW TURGOR PRESSURE.TO COMPARE AND ANALYZE THE ABILITY OF TURGOR REGULATION OF VT AND VD,CELLULAR IONIC COMPOSITION WAS DETERMINED BY MEANS OF NEWLY IMPROVED ION CHROMATOGRAPHY SYSTEM.IN THE PRESENCE OF 5mM Ca, AND UNDER BLUE LIGHT,VT REGAIN ITS ORIGINAL TURGOR BY ABSORBING MAINLY Na^+ AND Cl^-. IN SORBITOL-MEDIUM,HOWEVER,VT,BEING A Na-PLANT,CANNOT REGULATE TURGOR,BECAUSE OF LACK OF Na. UNDER WHITE LIGHT CONDITION (12L/12D) VT PARTIALLY LOOSES ITS ABILITY TO REGULATE TURGOR,BUT NOT VD.VD,SUPPOSED TO BE A K-PLANT , ABSORBS MUCH K^+, Na^+, Cl^-, AND SO_4^<2-> TO REGULATE ITS TURGOR.IT HAS TURGOR AT THE EXTERNAL OSMOLARITY AS HIGH AS 400mOsm. THE PRESENT RESULTS STRONGLY SUGGEST THAT THE EXPRESSION OF NEGATIVE PHOTOTROPISM OF VAUCHERIA IS LINKED WITH THE FAILURE OF TURGOR REGULATION OR SUSTAINED LOW TURGOR PRESSURE.THE UNDERLYING MECHANISM BETWEEN THE SENSING OF LOW TURGOR AND EXPRESSION OF NEGATIVE PHOTOTROPISM AWAITS FURTHER INVESTIGATION.