An Analysis of Assimilate Transport into Developing Wheat Grains

植物的生长依赖于光合作用产生的有机物质，主要是糖和氨基酸。乍一看，似乎有理由认为植物的生长速度应该直接取决于这些底物的浓度：它们的浓度越高，生长速度就越快。然而，这一假设并没有得到现有证据的支持。特别是年轻的种子，似乎保持着预设的生长速度，这与糖和氨基酸的浓度几乎没有关系。相反，生长速度似乎是由这些物质从传导细胞运输到正在发育的胚胎中控制的，距离不到一毫米。发展小麦籽粒为研究这种运输提供了有利条件，因为这条途径定义得很清楚，可以在沿途的关键点测量生长速度和浓度。这些研究将更好地了解这一途径的运输，从而更好地了解如何控制种子的生长速度。

Plant growth depends on the production of organic materials, mostly sugars and amino acids, by photosynthesis. At first consideration, it seems reasonable to suppose that the rate of plant growth should depend directly on the concentration of these substrates: the higher their concentration, the faster the rate of growth. However, this supposition is not supported by available evidence. Young seeds, especially, seem to maintain preset growth rates that show little relation to sugar and amino acid concentrations. Instead, growth rates appear to be controlled by the transport of these substances from conducting cells into the growing embryo, a distance of less than a millimeter. Developing wheat grains offer advantages for studying this transport, since the pathway is well- defined and growth rates and concentrations can be measured at key points along the path. These investigations will develop a better understanding of transport along this pathway and, consequently, of how the growth rate of seeds might be controlled.//