Hormonal Mediation of the Light Control of Internode Extension Using Pea Genotypes

光照使茎的生长速率显著降低。戴维斯博士建议研究从暗光到红光过渡后激素变化与生长动力学的关系，以确定内源性激素的变化在多大程度上、以何种方式介导光诱导的茎生长速率变化。红光将被用来减少白光固有的复杂性。戴维斯博士将使用一系列已知赤霉素（GA）含量的豌豆长度基因型。所有的基因型在黑暗中都比在光照下生长得快，但在光照下生长速度的比例降低有所不同。在一些基因型中没有GAs，但它们很高；在这些植物中，他发现吲哚乙酸（IAA）含量非常高。他有相当多的证据表明，GA可能通过诱导色氨酸消旋酶产生d -色氨酸而起作用，d -色氨酸是IAA的前体。在已知光谱组成的黑暗和照明条件下，以及在激素和抑制剂的作用下，通过位置传感器记录生长动力学。GAs， IAA和IAA共轭物将通过气相色谱-质谱法测定，IAA合成途径的成分将被分析。这将显示光在GA和IAA代谢途径中起作用的点，以及光诱导GA水平的变化是否实际上通过改变IAA水平来起作用。光照会使以前在黑暗中生长的植物的茎部生长减慢。这种现象发生的机制尚不清楚。一种可能是光线改变了植物激素的水平。为了确定是否与植物激素有关，我们需要知道光诱导生长减少的速率，然后检查植物激素内部水平的变化，看看它们是否同时发生变化。戴维斯博士将测量不同茎长豌豆品种的生长变化率和激素含量。茎长的差异是由基因控制的，并且已经被证明是由于对被称为赤霉素的植物激素的水平或反应的变化。也有证据表明，这种激素可能以某种方式在另一种激素吲哚乙酸的合成中相互作用。戴维斯博士将测量赤霉素和吲哚乙酸内部水平的变化，以确定光线是否以及如何导致茎生长减少。这将提高我们对植物如何生长的认识。

Light causes a pronounced decrease in stem growth rate. Dr. Davies proposes to investigate the kinetics of hormonal changes in relation to the growth kinetics following the transition from dark to red light in order to determine to what extent, and in what manner, changes in endogenous hormones may mediate light- induced changes in stem growth rate. Red light will be used to reduce the complexity inherent in white light. Dr. Davies will use a range of pea length genotypes whose gibberellin (GA) content is known. All of the genotypes grow faster in the dark than in the light but vary in the proportional reduction in their growth rate in the light. In some genotypes GAs are absent yet they are tall; in such plants he finds a very high indoleacetic acid (IAA) level. He has considerable evidence that GA may act via the induction of tryptophan racemase causing the production of D-tryptophan, which is then the precursor of IAA. The kinetics of growth are recorded by position transducers under darkness and illumination of known spectral composition, and following hormone and inhibitor applications. GAs, IAA and IAA conjugates, will be measured by gas chromatography-mass spectrometry and components of the IAA synthesis pathway assayed. This will show the point(s) in the GA and IAA metabolic pathways at which light acts, and whether a light induced change in GA levels in fact operates by altering the level of IAA. %%% Light causes a decrease in the growth of stems of plants previously grown in the dark. The mechanism by which this occurs is unknown. One possibility is that light alters the level of plant hormones. To determine whether plant hormones are involved one need to know the rate at which light induces a decrease in growth, and then examine the changes in the internal levels of the plant hormones to see if they change at the same time. Dr. Davies will measure the rate of growth change and hormonal content in pea varieties which have different stem lengths. The difference in stem lengths is genetically controlled, and has been shown to be due to changes in levels or responsiveness to plant hormones called gibberellins. There is also evidence that this hormone may interact in some way in the synthesis of another hormone, indoleacetic acid. Dr. Davies will measure the changes in the internal levels of gibberellin and indole acetic acid to determine if and how light causes a decrease in stem growth. This will improve our knowledge of how plants grow.