The Effect of Plants on Mineral Weathering

This paper is centered on the specific effects of plants on the soil weathering environment; we attempt to address how to quantify this component of the ecosystem and assess feedbacks between plants and weathering processes that influence the degree and rates of mineral weathering. The basic processes whereby plants directly influence the soil chemical environment is through the generation of weathering agents, biocycling of cations, and the production of biogenic minerals. Plants may indirectly influence soil processes through the alteration of regional hydrology and local soil hydrologic regime which determines the residence time of water available for weathering. We provide a brief review of the current state of knowledge regarding the effects of plants on mineral weathering and critical knowledge gaps are highlighted. We summarize approaches that may be used to help quantify the effects of plants on soil weathering such as state factor analyses, mass balance approaches, laboratory batch experiments and isotopic techniques. We assess the changes in the soil chemical environment along a tropical bioclimatic gradient and identify the possible effects of plant production on the soil mineralogical composition. We demonstrate that plants are important in the transfer of atmospheric carbon dioxide into the mineral weathering cycle and speculate how this may be related to ecosystem properties such as NPP. In the soils of Hawaiian rainforests subjected to deforestation, pasture grasses appear to change the proportion of non crystalline to crystalline minerals by altering the soil hydrologic regime or partitioning silica into more stable biogenic forms. A better understanding of the relationship between soil weathering processes and ecosystem productivity will assist in the construction predictive models capable of evaluating the sensitivity of biogeochemical cycles to perturbations.     

The Inhibition of Cell Division in the Mesocotyl of Etiolated Oat Plants by Light of Different Frequencies

Cell division taking place in the nodal meristem of etiolatedoat (Avena sativa cultivar Victory) seedlings is shown to bealmost uniformly sensitive to different wavebands of light inthe visible spectrum. The significance of the observations inrelation to the identity of the photoreceptor, and to the opinionthat green light is ‘morphogenetically inactive’is discussed.     

"观察SO2对植物的影响"实验的改进

介绍了对人民教育出版社的高中生物学必修教材第2册103页,实验12“观察二氧化硫对植物的影响”的部分改进。利用洗净的金龙鱼牌5L塑料油瓶和洗净的空矿泉水瓶等废旧物资进行实验操作。材料易于寻找,成本低廉,培养了学生“变废为宝”的节约思想;用NaOH溶液吸收装置内的SO2,避免了环境污染,培养了学生的环保意识。     

The Effect of Phosphinothricin (Glufosinate) on Glutathione Synthesis in Plants

The inhibitory effect of DL-phosphinothricin (glufosinate) on glutathione synthesis was studied in vivo and in vitro. The influence of phosphinothricin on γ-glutamylcysteine synthetase was compared with the already known effects of l -buthionine sulfoximine and l -methionine sulfoximine. The results showed that phosphinothricin and buthionine sulfoximine are inhibitors of γ-glutamylcysteine synthetase of plants. With both substances the enzyme was inhibited by 50 % at a concentration of 7 . 10^?4M (pI₅₀ = 3.15). Methionine sulfoximine reduced the enzyme activity by 50% at 5 . 10^?2 M (pI₅₀ = 1.30). It is discussed that the target enzyme of phosphinothricin is the glutamine synthetase whereas the γ-glutamylcysteine synthetase is only an accessory target.     

Flower Development and the Evolution of Self-fertilization in <Emphasis Type="Italic">Amsinckia</Emphasis>: The Role of Heterochrony

We studied the development of 26 flower traits under natural conditions in three clades of the genus Amsinckia (Boraginaceae). Each clade contained both a derived highly self-fertilizing taxon and an ancestral more highly outcrossing taxon. The more outcrossing taxa contained two flower morphs—pins and thrums—with opposite positioning of the sex organs (heterostyly). The highly selfing taxa had smaller flowers with sex organs in close proximity (homostyly). Growth trajectories were quantified over the entire or nearly the entire period from primordium initiation to flower opening. These trajectories were compared in the heterochronic framework and, in contrast with previous studies, character size was tracked over time rather than relative to another character. We focused on three hypotheses: (1) The distinct developmental trajectories leading to pins and thrums should be similar in all clades, while the trajectories leading to homostylous flowers might differ among clades. This was supported. Specifically, contrasting growth rates of stamen and pistil heights in heterostylous flowers caused pin and thrum flowers to have the reciprocal arrangement of anther and stigma heights. From the viewpoint of heterochrony, the decreased size (paedomorphosis) of the homostylous morph, compared to pins and thrums, resulted from decreased growth rate (neoteny) and earlier offset (progenesis) in all clades. Nevertheless, multiple heterochronic processes were involved in the mosaic development and evolution of homostylous flowers. (2) We tested the hypothesis that small, self-fertilizing flowers have reduced development times, one of the proposed selective advantages of increased self-fertilization rates. We found in contrast that developmental duration of homostylous flowers was either the same (two clades) or longer (one clade) compared to duration of pins and thrums. (3) Finally, we tested von Baer’s Law, which proposes that developmental differences among closely related taxa should arise later in development than differences among more distantly related taxa. Von Baer’s Law was supported strongly among homostyles, moderately among thrums and weakly among pins.     

Effect of Temperature on Carbohydrate Metabolism in Potato Plants

The effect of temperature on partitioning of newly fixed ¹⁴Cbetween the various carbohydrate fractions was studied in differentplant organs of three potato varieties. Incorporation of ¹⁴Cinto starch in the tubers was reduced at high temperatures,but the amount of labelled sucrose increased. In all varietiesthe incorporation of ¹⁴C into the cell wall components in theapex of the plant and in the stem, as well as its incorporationinto starch in the stem, was increased at high temperatures.The variety Norchip, which was found to be less sensitive tohigh temperature as indicated by carbon translocation to thetubers, was found to be less affected also in terms of ¹⁴C incorporationinto starch in the tubers. We suggest that high temperatureaffects carbon metabolism in the various plant organs and theresulting changes are associated with the change in the partitioningof assimilates between these organs.     

Effect of Thiolactomycin on Lipid Synthesis in Higher Plants

The effect of thiolactomycin (TLM), an inhibitor of type IIfatty acid synthase, on lipid synthesis in greening tissueswas examined. Pulse-chase experiments with Na[1-¹⁴C]acetatefor greening Avena leaves showed that continuous administrationof TLM (100µg/ml) decisively reduced phosphatidylcholine(PC) synthesis from acetate and blocked the subsequent conversionof PC to monogalactocyldiacylglycerol (MGDG), whereas temporaladministration of TLM (100 µ/ml) reduced PC synthesisfrom acetate by only 50% and did not block the conversion ofPC to MGDG. In the reduced PC synthesis, the ratio of oleicto palmitic acid decreased at earlier stages of greening, reflectingmore suppression of oleic acid synthesis. In later greeningstages the modulated fatty acid composition recovered to thenormal composition. In further steps, the fatty acid compositionwas not affected by TLM throughout the greening stages. Greeningof either etiolated Avena leaves or etiolated Brassica cotyledonsin the presence of TLM led to a marked decrease in the contentsof MGDG, digalactosyldiacylglycerol (DGDG) and phosphatidylglycerol(PG), but only a small change in the fatty acid compositionof their lipids. The only inhibition characteristic of TLM wasthe desaturation of palmitic to 3-trans-hexadecenoic acid inAvena leaf PG. These results suggest the presence of a mechanismby which the modulated fatty acid composition of lipids is normalizedin the flow of the synthesis. Electron microscopic observationsshowed that Avena chloroplasts developed into round forms ratherthan normal ellipse forms and the thylakoid membranes of Brassicachloroplasts were abnormally swollen everywhere in the presenceof TLM. Photosynthetic oxygen evolution in both tissues wasnot inhibited. (Received December 26, 1986; Accepted April 24, 1987)     

Estimation of Recombination Frequencies and Construction of RFLP Linkage Maps in Plants from Crosses between Heterozygous Parents

The construction of a restriction fragment length polymorphism (RFLP) linkage map is based on the estimation of recombination frequencies between genetic loci and on the determination of the linear order of loci in linkage groups. RFLP loci can be identified as segregations of singular or allelic DNA-restriction fragments. From crosses between heterozygous individuals several allele (fragment) configurations are possible, and this leads to a set of formulas for the evaluation of p, the recombination frequency between two loci. Tables and figures are presented illustrating a general outline of gene mapping using heterozygous populations. The method encompasses as special cases the mapping of loci from segregating populations of pure lines. Formulas for deriving the recombination frequencies and information functions are given for different fragment configurations. Information functions derived for relevant configurations are also compared. A procedure for map construction is presented, as it has been applied to RFLP mapping in an allogamous crop.     

The Frequencies of the Genes of Low-Molecular-Weight Alanine-Rich Cold Shock Proteins and Variation of Their Primary Structure in Plants of Temperate Climate

Polymerase chain reaction (PCR) was used to study the frequencies of the gene of a low-molecular-weight alanine-rich cold shock protein in plants of temperate climate. This gene was demonstrated to be specific for the family Cruciferae. Its variability in this family was studied.     

Frequencies of Dental Anomalies and Their Potential Effect on Determining MNI Counts

Abstract

An examination of the distribution and morphology of supernumerary teeth in North American Bovidae and Cervidae indicates their expected frequency of occurrence in archaeological sites and potential effect on MNI counts.