cytoskeleton, but most signals appear to induce altered gene expression through activation or repression of gene transcription. Plant cells contain two information systems(figure 7-2). The genetic information system flow in plant cells, DNA RNA protein phenotype, implies a certain rigidity and simplicity in result. In these cases, a direct relationship exists between the expression of a single gene and the phenotypic character it specifies, such that environmental variation has little impact on expression of the gene. Few genes, however, are unaffected by environmental factors. For example, the genes that specify flower color or seed morphology are invariant in expression under many different conditions of growth and development. In the epigenetic information system, the expression of many genes, forinstance, genes that control important phenotypic characteristics including production of biomass, duration of growth, branching, and responses to stress, are strongly modified by the environment in which the plant grows. a phenotypic character results from complex interactions involving one or more genes and environmental influences that impact signal transduction networks. These characters vary with the plants environment 二植物对信号刺激的反应 植物对刺激的反应根据植物发育阶段,之前所经历的环境条件,刺激发生的季节 和时间等的不同而变化。成熟细胞产生的反应可能是生理和生化的,而生长中的 细胞产生的反应可能是形态上和发育上的。植物对信号刺激的反应有的很快,有 的比较慢。有些反应,如触动含羞草引起叶片合拢,只需几秒钟,而有些通过 基因表达的改变引起形态和发育变化的反应需要几天时间才能发生。快反应和慢 反应都是通过基本的信号网络传递机制实现,都是信号的感受与传递的结果。有 些反应是通过多条信号传递途径相连形成最终的生理变化。例如:干旱引起植物 根部的水分胁迫,诱导编码植物激素脱落酸(ABA)合成途径所需酶的基因的激 活。ABA然后引发一连串的信号传递活动最终导致保卫细胞中的离子外流,导致 保卫细胞的关闭。降低蒸腾保存水分 The signals impact the cell at different sites and are perceived by different receptors Plant responses to stimulus are modulated by developmental age, previous environmental experience, and internal clocks that specify the time of year and the time of day. For mature plant cells, the response can be physiological and biochemical for growing cells, it can be morphological and developmental. The response to signal stimulus can be very quick or slow. Some responses, e.g., touch-induced leaflet drop of Mimosa, occur in seconds. Others, such as shifts in gene expression that changes morphology and development, may take days. Both fast and slow responses use the same basic transduction network machinery, and both are downstream results of a perceived stimulus. Several signal transduction pathways can be linked to bring about a final physiological change. For instance, drought imposes water stress on the roots of a plant, inducing the activation of genes encoding enzymes that synthesize the plant hormone abscisic acid(ABA). ABa then initiates a cascade of events that eventually results in the efflux of ions from the guard cells, thereby causing stomatal closure to minimize transpiration and conserve watercytoskeleton, but most signals appear to induce altered gene expression through activation or repression of gene transcription. Plant cells contain two information systems (figure 7-2). The genetic information system flow in plant cells, DNA→ RNA→ protein → phenotype, implies a certain rigidity and simplicity in result. In these cases, a direct relationship exists between the expression of a single gene and the phenotypic character it specifies, such that environmental variation has little impact on expression of the gene. Few genes, however, are unaffected by environmental factors. For example, the genes that specify flower color or seed morphology are invariant in expression under many different conditions of growth and development. In the epigenetic information system, the expression of many genes, forinstance, genes that control important phenotypic characteristics including production of biomass, duration of growth, branching, and responses to stress, are strongly modified by the environment in which the plant grows. A phenotypic character results from complex interactions involving one or more genes and environmental influences that impact signal transduction networks. These characters vary with the plant’s environment. 二植物对信号刺激的反应 植物对刺激的反应根据植物发育阶段，之前所经历的环境条件，刺激发生的季节 和时间等的不同而变化。成熟细胞产生的反应可能是生理和生化的，而生长中的 细胞产生的反应可能是形态上和发育上的。植物对信号刺激的反应有的很快，有 的比较慢。有些反应，如触动含羞草引起叶片合拢，只需几秒钟， 而有些通过 基因表达的改变引起形态和发育变化的反应需要几天时间才能发生。快反应和慢 反应都是通过基本的信号网络传递机制实现，都是信号的感受与传递的结果。有 些反应是通过多条信号传递途径相连形成最终的生理变化。例如：干旱引起植物 根部的水分胁迫，诱导编码植物激素脱落酸（ABA）合成途径所需酶的基因的激 活。ABA 然后引发一连串的信号传递活动最终导致保卫细胞中的离子外流，导致 保卫细胞的关闭。降低蒸腾保存水分。 The signals impact the cell at different sites and are perceived by different receptors. Plant responses to stimulus are modulated by developmental age, previous environmental experience, and internal clocks that specify the time of year and the time of day. For mature plant cells, the response can be physiological and biochemical; for growing cells, it can be morphological and developmental. The response to signal stimulus can be very quick or slow. Some responses, e.g., touch-induced leaflet drop of Mimosa, occur in seconds. Others, such as shifts in gene expression that changes in morphology and development, may take days. Both fast and slow responses use the same basic transduction network machinery, and both are downstream results of a perceived stimulus. Several signal transduction pathways can be linked to bring about a final physiological change. For instance, drought imposes water stress on the roots of a plant, inducing the activation of genes encoding enzymes that synthesize the plant hormone abscisic acid (ABA). ABA then initiates a cascade of events that eventually results in the efflux of ions from the guard cells, thereby causing stomatal closure to minimize transpiration and conserve water