FORMATION AND MORPHOLOGY OF AN IRON PLAQUE ON THE ROOTS OF TYPHA LATIFOLIA L. GROWN IN SOLUTION CULTURE

Roots of Typha latifolia L. exposed to Fe²⁺ under reduced conditions in solution culture developed visible coatings (plaques) of an oxidized Fe compound that extended as much as 15-17 μm into the rhizosphere. Iron concentrations were significantly less and discoloration was not apparent on the surface of roots exposed to Fe-(BPDS)₃, Fe³⁺, Fe-EDDHA, and Fe-EDTA. The extent of plaque formation increased with the concentration of Fe²⁺ in solution and with pH of the solution in the range of 3.0 to 4.6. Above pH 4.6, oxidation of Fe²⁺ in the culture solution may have reduced precipitation of Fe on the root surface. Plaque development was most extensive approximately 1.0 cm from the root tip, but all root surfaces showed some Fe staining. Scanning electron micrographs of plaqued roots, grown both in solution culture and in the field, provided support for a model of cast formation by oxidation and precipitation of Fe on external cell surfaces.     

静止和充气培养条件下短期紫外辐射对钝顶螺旋藻光化学效率的影响

为了研究短期太阳紫外辐射对钝顶螺旋藻的影响,作者将静止和充气培养的藻体,暴露在全波长太阳辐射PAB(PAR UVA UVB),去除UVB辐射PA(PAR UVA)及切断所有紫外辐射的光合有效辐射P(PAR)三种光处理条件下,测定了其光化学效率的变化。结果表明,紫外辐射(UVP)及光合有效辐射(PAR)均能导致钝顶螺旋藻的光化学效率降低,表现出了明显的光抑制,但是,UVR可导致更大程度的光抑制。充气培养条件下,与早晨(07:00)初始值相比,PAR导致了11%~20%的光抑制,而UVR(PAB-P)所产生的额外光抑制占9%~31%;静止培养条件下,UVR的存在使得螺旋藻的光化学效率趋近于零(无法检出)。在两种培养条件下,藻细胞所受最大光抑制均发生在中午,下午(17:00)表现出不同程度的恢复。紫外辐射使得类胡萝卜素及藻蓝蛋白与叶绿素a含量的比例增大。与PAB和P相比,PA处理使得螺旋藻类胡萝卜素和藻蓝蛋白与叶绿素含量之比明显升高,UVA可能会诱导类胡萝卜素及藻蓝蛋白的合成。     

L-精氨酸与精胺延缓大麦离体叶片衰老效应的比较

L-精氨酸和精胺均具有延缓大麦离体叶片叶绿素、蛋白质和核酸含量下降的作用。L-精氨酸具有良好的渗透性和移动性。但其最适浓度高于精胺100倍,作用时间也滞后于精胺。L-精氨酸可使叶片内多胺含量增加,多胺合成抑制剂ABA则削弱L-精氨酸延缓叶片衰老的作用。L-精氨酸转变成具有强烈生理活性的多胺可能是其作用机理之一。     

The Absorption of Ions by Excised Root Systems: II. OBSERVATIONS ON ROOTS OF BARLEY GROWN IN SOLUTIONS DEFICIENT IN PHOSPHORUS, NITROGEN, OR POTASSIUM

1. Barley plants were grown in complete culture solution and indeficiencies of phosphorus, nitrogen, or potassium for a periodof about 6 weeks. Excised roots of these plants were treatedwith a complete, aerated culture solution at 25? C. for varyingperiods of time, and the changes in respiration rate, phosphorus,nitrogen, potassium, sugars, and starch contents measured.
2. Therewere changes in fresh weight and dry weight of the excisedrootsduring treatment. The dry weight decreased with time butthewater-content changes were variable. There was a gain orlossof water by the roots according to the treatment.
3. In all casesthe deficient roots increased in content of theelement in whichthey were originally deficient. The roots ofthe plants suppliedwith full nutrient usually decreased incontent of phosphorus,nitrogen, and potassium, but exceptionsoccurred and the reasonsare discussed.
4. In most of the experiments described simultaneousloss of oneion and gain of another occurred.
5. Nitrogen-deficientroots accumulated nitrate when exposed toa complete nutrientsolution, and some of this was assimilatedwith formation ofprotein. Under similar conditions nitrogen-richroots decreasedin nitrogen content and proteolysis took place.
6. There wasa rapid fall in sucrose and reducing sugar contentof the excise'roots. The starch content was initially verysmall and showedlittle change with time.
7. The respiration rate declined withtime in all treatments exceptwhere a nitrogen deficiency existed.Here the respiration rateincreased to a maximum value at about8 hours and then fell.This increase in rate is attributed toprotein synthesis. Noevidence of a ‘salt respiration’was observed evenwhen active uptake of phosphorus or potassiumwas occurring.
8. In most instances the carbon dioxide evolvedin respirationgreatly exceeded the carbon dioxide equivalentof the sugarconsumed in the same period. Exceptions were foundwith thenitrogen-deficient roots where less carbon dioxidewas evolvedthan the equivalent of sugar consumed. It is probablethat apart, at least, of the sugar unaccounted for was usedin proteinsynthesis.
9. Where the carbon dioxide of respirationwas in excess of theequivalent of sugar consumed, protein oramino-acid is the mostprobable substrate. Respiration rateis found to be relatedboth to nitrogen and sugar content.

     

大麦根中禾谷多粘菌休眠孢子堆的超微结构*

通过扫描电镜和透射电镜观察了禾谷多粘菌PolymyxagraminisLed．休眠孢子堆的超微结构。休眠孢子堆仅分布于寄主根表皮细胞中。休眠孢子堆形状不一,有的呈球状,有的呈律状,少则由几十个,多则由数百个紧密排列的休眠孢子组成。休眠孢子彼此通过刺突连接,细胞壁分4层,第三层局部区域结构松散,可能与初生游动孢子萌发孔有关。成熟休眠孢子细胞质丰富,细胞质膜内侧含有大量脂质粒,细胞质中央含一个细胞核,围围分布线粒体、内质网、高尔基体、液泡等细胞器。成熟的休眠孢子在越夏前大多数已释放初生游动孢子,只剩下空壳。表面凹陷是已释放游动孢子的休眠孢子一个特征。本文还讨论了禾谷多粘菌休眠孢子在病害流行学中的作用。     

大麦根中禾谷多粘菌休眠孢子堆的超微结构

通过扫描电镜和透射电镜观察了禾谷多粘菌PolymyxagraminisLed．休眠孢子堆的超微结构。休眠孢子堆仅分布于寄主根表皮细胞中。休眠孢子堆形状不一,有的呈球状,有的呈律状,少则由几十个,多则由数百个紧密排列的休眠孢子组成。休眠孢子彼此通过刺突连接,细胞壁分4层,第三层局部区域结构松散,可能与初生游动孢子萌发孔有关。成熟休眠孢子细胞质丰富,细胞质膜内侧含有大量脂质粒,细胞质中央含一个细胞核,围围分布线粒体、内质网、高尔基体、液泡等细胞器。成熟的休眠孢子在越夏前大多数已释放初生游动孢子,只剩下空壳。表面凹陷是已释放游动孢子的休眠孢子一个特征。本文还讨论了禾谷多粘菌休眠孢子在病害流行学中的作用。     

中西方旧石器文化中的技术模式的比较

对中西方旧石器文化中技术模式的比较表明,两者间存在很大的差别,充分显示了中国旧石器文化发展的特殊性以及中西方整个旧石器文化属于不同的传统。     

三裂叶野葛毛状根的培养及其葛根素的产生

发根农杆菌ATCC15834感染三裂叶野葛叶片外植体20天后,从其切口叶脉处产生的愈伤组织上产生毛状根。感染35天后约85%的叶片外植体产生毛状根。毛状根能在无外源生长调节剂的MS固体和液体培养基上自主生长,但在液体培养基中培养的毛状根生长更迅速,也不会形成愈伤组织。毛状根线粒体膜电势的荧光染色结果表明,液体培养的毛状根细胞线粒体的膜电势比固体培养的毛状根高11.8倍。PCR结果证实,发根农杆菌Ri质粒的rolB和rolC基因已在三裂叶野葛毛状根基因组中整合并得到表达。HPLC测定结果表明,三裂叶野葛毛状根中的葛根素含量约为对照根(种子萌发产生的幼苗根)的2.5倍,达1.190 mg/g.dry.wt;并比多年生葛根生药片的葛根素含量高6.7%。