The future for plants and plants for the future

A report of the 2007 EMBO Conference Series on Plant Molecular Biology 'From basic genomics to systems biology', Ghent, Belgium, 2-4 May 2007.     

Herbicides and plants

Summary

Herbicide activity depends upon the inherent ability of the active ingredient (AI) to interact with the target enzyme(s) and the efficiency of its delivery at the target site(s). In this paper consideration is given to the factors which influence effective target site delivery and activity of foliage and soil-applied compounds. In the case of foliage- applied herbicides, the efficiency of retention and cuticle penetration is influenced by the stage and habit of growth of the plant, leaf age and surface characteristics, the molecular and formulation features of the AI, and the environmental conditions before, during, or after spraying. These factors may influence the efficiency of uptake, translocation and metabolism of AI en route to the target sites. The action of soil-applied compounds is influenced by the physico-chemical properties of the AI, its adsorption/desorption on the clay-humus colloidal complex, and the absorption, transport and metabolism en route to the target sites. In particular the water solubility of the AI, its formulation and the climate conditions subsequent to spraying, may influence selectivity and environmental fate. Finally, the ability of plants to acquire herbicide tolerance is considered in relation to both crop and weed with particular reference to the mechanisms which can be used to induce tolerance in crop plants.     

Rhizosphere communication of plants, parasitic plants and AM fungi

Plants use an array of secondary metabolites to defend themselves against harmful organisms and to attract others that are beneficial. However, the attraction of beneficial organisms could also lead to abuse by malevolent organisms. An exciting example of such abuse is the relationship between plants, beneficial mutualistic arbuscular mycorrhizal fungi and harmful parasitic plants. Signalling molecules called strigolactones, which are secreted by plant roots in low concentrations, induce the growth of both obligate biotrophs. Here, we review the importance of strigolactones for these two interactions and discuss possible developments that should further clarify the role of these signalling molecules in rhizosphere processes.     

Singlet oxygen and plants

The generation, occurrence and action of singlet oxygen in plant tissue is reviewed. Particular emphasis is placed upon its formation from triplet sensitizers and its reactivity with molecules of biological importance such as lipids and amino acids. The possibility of singlet oxygen generation in chloroplasts is discussed in relation to potential quenching systems such as carotenoid pigments, ascorbate and α-tocopherol. The problems associated with carotenoid diminution and some stress and herbicide treatment conditions are related to the possibility of damage by singlet oxygen. The action of a number of secondary plant substances, including quinones, furanocoumarins, polyacetylenes and thiophenes, as plant defence agents is discussed in relation to the photodynamic generation of singlet oxygen.     

How plants see themselves--self-incompatibility in flowering plants

Plants have been propagating themselves by cloning for millennia. It is, however, widely recognised that mixing genes with other individuals of the same species makes better evolutionary sense, as it provides the variation that is the raw material for natural selection. How, then, do some plants prevent self-fertilisation?     

入侵植物的繁殖策略以及对本土植物繁殖的影响

理解入侵生物的繁殖策略是阐明生物入侵机制的一个重要方面。入侵植物常表现出一些共同的繁殖特征, 如以两性花为主的性系统、自动自交为主的繁育系统或不依赖传粉媒介的无融合生殖和无性繁殖以及高生殖投资的资源配置策略等。成功入侵的外来植物通过影响本土的传粉者, 在种群和群落水平上影响本土植物的有性繁殖, 甚至促使某些本土植物在繁殖对策和表型性状上发生快速转变。目前, 入侵植物繁殖策略及其生态效应的研究多侧重于入侵种的快速演化, 而有关外来植物与本土植物间的相互影响及其可能存在的协同适应研究还较为缺乏。探讨本土植物在外来种入侵压力下的繁殖对策和响应机制, 将丰富人们对物种间竞争、共存及群落构建等机制的深入了解。从繁殖和适应的角度探求入侵植物与本土植物之间的复杂关系, 将有助于解析生物入侵的机制及人类干扰下的物种演化规律, 也为预测和防控入侵植物提供科学依据。     

Simultaneous parsimony jackknife analysis of 2538rbcL DNA sequences reveals support for major clades of green plants, land plants, seed plants and flowering plants

The ever-larger data matrices resulting from continuing improvements in DNA sequencing techniques require faster and more efficient methods of phylogenetic analysis. Here we explore a promising new method, parsimony jackknifing, by analyzing a matrix comprising 2538 sequences of the chloroplast generbcL. The sequences included cover a broad taxonomic range, from cyanobacteria to flowering plants. Several parsimony jackknife analyses were performed, both with and without branch-swapping and multiple random addition sequences: 1) including all positions; 2) including only first and second codon positions; 3) including only third positions; and 4) using only transversions. The best resolution was obtained using all positions. Removal of third positions or transitions led to massive loss of resolution, although using only transversions somewhat improved basal resolution. While branch-swapping improved both resolution and the support found for several groups, most of the groups could be recovered by faster simple analyses. Designed to eliminate groups poorly supported by the data, parsimony jackknifing recognizes 1400 groups on the basis of allrbcL positions. These include major taxa such as green plants, land plants, flowering plants, monocots and eudicots. We include appendices of supported angiosperm families, as well as larger groups.