盐胁迫下外源ABA对玉米幼苗耐盐性的影响

利用不同浓度外源ＡＢＡ 可以提高生长在盐渍条件下玉米（Ｚｅａ ｍ ａｙｓ Ｌ．）幼苗的耐盐能力,增加幼苗的干重。其原因是由于幼苗渗透势的降低和渗透调节能力的增大,地上部分拒盐能力的提高,摄取的大量Ｎａ＋ 积累在根部。同时发现外源ＡＢＡ 增大幼苗渗透势和渗透调节能力是幼苗有机渗透物质增加的结果。讨论了玉米地上部分拒盐的机理     

FREEZING POINTS OF ANTI-COAGULANT SALT SOLUTIONS

By a method involving equilibration of ice and solution, and analysis of the solution, freezing point depressions of solutions of sodium citrate, oxalate, and fluoride have been determined over the range Δ = 0.45 to 0.65°C. Determinations with sodium chloride solutions have confirmed the accuracy of the method. In each case the freezing point depression is given, within 0.002°C., as a linear function of the concentration. By the use of these linear equations it is possible to prepare a solution of any of these four salts isotonic with a given biological fluid of known freezing point, provided the latter falls within the range studied.     

四倍体刺槐的抗盐性

 以四倍体刺槐(Robinia pseudoacacia)为主要试验材料,以二倍体刺槐为对照材料,在两种盐胁迫下,对苗木的形态、生理生化、光合特性和解剖结构等指标的变化规律进行了研究。利用NaCl和Na₂SO₄盐溶液对两种刺槐进行盐处理,在30 d后每7 d处理1次,共处理4次,并在处理前和处理后每7 d进行各项指标的测定。结果发现：1)在盐胁迫下二倍体刺槐的植株生长受到强烈抑制,叶片含水量和叶绿素含量显著低于对照,有明显的盐害症状;对四倍体刺槐植株的生长影响较小,叶片含水量和叶绿素含量也与对照差异不显著,无盐害症状。2)四倍体刺槐经过盐处理后相对电导率和脯氨酸(Proline, Pro)含量虽然也稍有上升,但与对照相比未达到显著水平,而二倍体刺槐显著高于对照;同时作为保护酶系统的过氧化物酶(Peroxidase, POD)、超氧化物歧化酶(Superoxide dismutase, SOD)、过氧化氢酶(Catalase, CAT)在四倍体刺槐经盐胁迫后期也保持了较高的活性,从而提高了其抗盐性,而对盐敏感的二倍体刺槐3个保护酶活性均较低。 3)经盐胁迫后对四倍体刺槐光合特性影响不大,净光合速率（Net photosynthetic rate, P_n）和胞间CO₂浓度（Intercellular CO₂ concentration, C_i）均无显著变化,而二倍体刺槐P_n和C_i显著下降。4)经盐胁迫后四倍体刺槐在解剖结构上做出了积极的反应：叶肉栅栏组织拉长、排列更为紧密、 海绵组织变小、排列紧密。而二倍体刺槐出现了相反的现象。综合以上分析认为：四倍体刺槐具有较强的抗盐性。     

TILLERING AND MORTALITY OF THE SALT MARSH CORDGRASS,SPARTINA ALTERNIFLORA

Recruitment and mortality of Spartina alterniflora tillers and culms were estimated from measurements of live standing crops at Wallops Island, Virginia. Stands of tall and medium form grass produced from 452 to 1,227 tillers m⁻² yr⁻¹. Those tillered in spring lengthened into culms their first year, while those tillered in late summer and fall may have overwintered and lengthened into culms their second year. Biennial growth was most prevalent in tall form Spartina. Fifty-six to sixty-one percent of all tillers died before lengthening into culms. Of the remainder, 9 to 56% died as culms before the time of flowering. Sixty-three percent of the surviving culms of tall form Spartina flowered, compared to only 14 to 23% in medium form. Mortality of tillers and culms removed 16 to 35% of the annual production of Spartina biomass from live standing crops before the time of flowering.     

血管紧张素对大鼠饮盐水行为的作用

在ＳＤ大鼠静脉内注入不同剂量的ＡｎｇⅡ后大鼠的饮盐水量明显增加，切除肾上腺的大鼠也出现强烈的饮盐水行为，但给予适当量的醛固酮可消除这种行为。脑室内注入巯甲丙脯酸可阻断静脉内给与ＡｎｇⅡ所引起的大鼠的饮盐水行为。本文对ＡｎｇⅡ的作用机理进行了探讨。     

盐效应对DNA大分子构象的影响

用CD光谱监测了Micrococcus luteus DNA在不同MgCl_2浓度下[θ]值的变化,发现随着MgCl_2浓度的增加,在275nm处其[θ]值减少;而在220—250nm处,其负[θ]值加大.这个结果表明DNA大分子在空间上趋于缩拢.在同样条件下也用紫外光谱进行了监测,发现随着MgCl_2浓度的增加,在260nm处有明显的减色效应出现,这便又进一步印证了上述结果.而又用Batch-2107微量热计进行了热力学上的研究,结果表明在上述条件下,随着DNA大分子在空间上缩拢程度的加大,则伴有较高的释热值.这便从热力学的角度进一步佐证了这样的结果:随着MgCl_2浓度的增加,使溶液中的DNA大分子在空间上产生明显的缩拢现象.同时,所有上述测定结果都一致表明:这种DNA大分子构象变化过程是时间依赖的,约持续10分钟.     

LIKING OF POPCORN CONTAINING DIFFERENT LEVELS OF SALT1

Approximately 300 subjects participated in a test to determine whether the level of salt in popcorn affected the change in overall liking observed as a consequence of consuming a serving of popcorn. Subjects tasted and rated three samples of popcorn (low, medium, high salt levels), ate a serving of popcorn at one of the salt levels and then tasted and rated the three samples again. Subjects returned one or seven days later and tasted and rated the samples again. Overall liking, salt intensity and salt liking were measured. The subjects also completed a questionnaire about their liking and consumption of popcorn. Liking scores for the popcorns decreased after eating a 3-cup serving; however, sensory specific satiety for the different levels of salt was not observed. Consuming low salt popcorn increased the rated saltiness of the popcorns, whereas consuming high salt popcorn decreased the rated saltiness — probably a frequency effect. When subjects retasted the popcorns one or seven days later, all liking ratings increased except the salt liking ratings for the high salt sample. There was also a trend for the overall liking of this high salt sample to increase less than for the medium and low salt samples. Questionnaire measures of liking or consumption were not related to the changes in liking observed.     

发状念珠藻对盐胁迫的响应

探讨了发状念珠藻(NostocflagelliformeBornetFlah)对盐胁迫的耐受适应机制,采用含不同浓度NaCl(0、01、02、04、06、08、10mol/L)的BG110培养液处理具有正常生理活性的丝状体,25±05℃,40μmol/m2/s下照光培养12h,测定藻体光合作用、呼吸作用等生理活性以及体内一些物质的含量,结果表明:随培养液中NaCl浓度的升高藻体光合作用、呼吸作用以及PSⅡ活性(Fv/Fm)降低;质膜透性不断增大,丙二醛含量升高,自由水含量、自由水/束缚水比值下降,类胡萝卜素、可溶性糖含量增加,脯氨酸含量变化不大。由此可知,盐胁迫下发状念珠藻正常生理活性受到抑制而表现出一定的抗逆能力;该藻对盐胁迫具有一定的耐受能力,类胡萝卜素的增加有助于清除藻体内的氧自由基,可溶性糖可能是其主要渗透调节物质之一,脯氨酸在盐胁迫中的渗透调节作用不大。       

AN ECOPHYSIOLOGICAL STUDY OF THE SALT SECRETION OF FOUR HALOPHYTES

Plants of Spartina anglica, Limonium vulgare, Armeria maritima and Glaux maritima were collected in the field and grown on different concentrations of NaCl, KCl and CaCl₂. Salt secretion, ion content, water content and transpiration rates were determined. The highest sodium secretion was found in Spartina anglica , a species from the most saline habitat; and a somewhat lower secretion rate in Limonium vulgare. The lowest rates were found in Glaux maritima and Armeria maritima. The sodium secretion efficiency, i.e. the ability to maintain an unchanged internal sodium content, was highest in Spartina anglica. Spartina anglica is the most successful in the removal of excessively absorbed salt, since it secretes 60% of the absorbed sodium. The values for Limonium vulgare, Glaux maritima and Armeria maritima were 33, 20 and 4% respectively. The species studied differ in the preferential sequence of ion secretion as well as in secretion rate and efficiency. This preferential sequence of ion secretion seems to be similar in members of the same taxonomic group (Plumbaginaceae). The comparability of the secretion parameters is discussed with regard to morphological differences between the species.     

THE SOIL FUNGI OF THE DOVEY SALT MARSHES

In this investigation of the fungi of the soil of the Dovey Salt Marshes (Ynyslas) 48 fungi were isolated.
Twelve of the species found do not appear to have been recorded before for the British Isles.
The area investigated is a badly aerated, stiff, tenacious clay, alkaline in reaction ( p H 8), with a high water content, due mainly to periodical inundations by tidal salt water.
Method of investigation consisted in taking samples of soil from a depth of 11/2 and 31/2 inches and either planting portions of this directly on to specially prepared media, or first shaking up a portion in water and then inoculating the prepared media with some of the suspension.
Three fungi– Torula allii, Penicillium hyphomycetis and Fusarium oxysporium var. resupinatum —were almost invariably present in every sample of soil: almost equally common were Trichoderma lignorum, T. Köningi, Hormodendron cladosporoides, Mucor circinelloides and Periconia felina .
Most of the fungi found are species found above ground as saprophytes, and may have been introduced into the soil by drainage, etc.
The writer considers fungi are active only in association with organic material.
The vegetation covering this marsh shows marked zonation: soil samples were chiefly taken from the Glycerietum and Aimerietum.
The same species of fungi were common to the two associations.
Glyceria maritima is a most effective silt binder, because the stele of its rhizomes and roots consists almost entirely of lignified tissue which does not yield to the activities of the soil fungi; Armeria maritima is not so effective a silt binder because the stele of its rhizomes and roots contains very little lignified tissue—at a depth of a foot, the tap roots of Armeria are little more than hollow tubes, the interiors having been removed by fungi and bacteria.     

ACCUMULATION OF SALT AND PERMEABILITY IN PLANT CELLS

1. Comparisons are made of concentrations of K and Br in exudates of barley roots and in expressed sap from roots, under conditions favorable for aerobic metabolism. Both methods lead to the same general viewpoint concerning metabolically governed transport of solutes by living plant cells. 2. Cyanide in low concentration prevented salt accumulation by barley roots. Methylene blue, without decrease of CO₂ production by roots, destroyed power of salt accumulation. 3. K and Br ions entered roots to only a slight extent under an anaerobic condition, even with an inward gradient of ionic concentration. 4. Lactate or alcohol, under aerobic conditions, did not prevent rapid accumulation of salt by root cells. 5. Experiments on fluids obtained by suction from tomato roots gave evidence of loss of salt-accumulating power under the influence of N₂ gas or CO₂ gas, together with probable effects on cell permeability. 6. Several experiments on Nitella cells in which radioactive isotopes were used are reported. Bromide gradually moved into vacuolar sap until the concentration appeared to exceed that of the protoplasm, on the basis of the results of the several types of experiments. Accumulation of salt in the vacuole did not occur anaerobically. 7. Some views of interrelations of permeability, salt accumulation, and metabolism are suggested for further discussion.     

干旱、盐和低温胁迫对水稻幼苗脯氨酸含量的影响

以三叶期的水稻幼苗为材料,研究了干旱（－０．６ＭＰａ ＰＥＧ模拟）、盐（０．１５ｍｌ／Ｌ ＮａＣｌ）和低温（６℃）胁迫下,不同水稻品种脯氨酸积累的变化。结果表明,干旱、盐和低温胁迫下稻苗均可积累脯氨酸,且随着胁迫时间的处长而加剧。在同一胁迫条件下,耐性强的品种脯氨酸积累较少,而敏感品种脯氨酸积累则较多。脯氨酸的积累不宜作为稻苗抗逆性的筛选指标。     

盐激条件下快生大豆根瘤菌的渗透调节

快生大豆根瘤菌(Rhizobium fredii)RTl9在基本培养基中能耐800 mmol/L。NaCl。该菌株在对数生长后期,突然加入高浓度NaCl,使其培养液中的NaCl最终浓度为1000mmol/L。5分钟后,细胞内谷氨酸的含量便急剧增加,而且脯氨酸也大量积累。50分钟后,它们的含量分别达到未受盐激的(对照)4倍和3.8倍。在盐激条件下,RTl9的谷氨酰胺合成酶(GS)和谷氨酸合成酶(GOGAT)的活性比对照明显提高。其中GS活性的提高主要是由GSⅡ引起的,GSI变化不大。将这两种酶直接暴露于1000mmol/LNaCl,50分钟后,酶活性降至原来的70％,并未完全失活。聚丙烯酰胺凝胶双向电泳的分析表明,若干蛋白质在盐激后消失,而且发现两种蛋白质是新合成的,其分子量和等电点(MW/pI)分别为110 kD/4.3和76 kD/6.5。