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

本文研究了淡水种Vaucheria terrestris（VT）和半咸水种V.dichotoma（VD）的向光反应调节与光调节能力的关系。VT耐盐性低，对50 W m ~ 2以上的白光呈负向光反应，而<-2>VD在海水中也能存活，对直射光呈正向光反应。Ca的加入显著提高了VT和VD的耐盐性，在高渗培养基中培养时，两种植物生长细胞的顶端直径减小，渗透压大于50 mOsm的NaCl和山梨醇诱导VT产生负向光性;另一方面，VD仅由山梨醇诱导，结果表明，光致反转和顶点偏移与低湍流压力是独立相关的，为了比较分析VT和VD的湍流调节能力，用新改进的离子色谱系统测定了细胞离子组成，在5 mM Ca存在下，在蓝光下，VT主要吸收Na^+和Cl^-，使其恢复原来的肿胀。在山梨醇培养基中，VT作为含钠植物，由于缺乏钠，不能调节胃脘痛。在白色（12 L/12 D）条件下，VT部分失去了调节膨润的能力，而VD则没有，VD是一种钾植物，它吸收大量的K^+、Na^+、Cl^-和SO_4 ~<2->-来调节膨润，在外部渗透压高达400 mOsm时仍有膨润作用。这些结果有力地表明，沃氏菌的负向光性表达与其蒸腾调节功能的丧失或持续的低蒸腾压有关，低蒸腾感与负向光性表达之间的内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.