Department of Biochemistry and Biophysics, Iowa State University, Ames, Iowa.
Plant Physiol. 1966 Sep;41(7):1119-29. doi: 10.1104/pp.41.7.1119.
The exchange of HTO with aerial portions of the soybean was studied under a variety of conditions. When fed to a lone leaf or leaflet in a saturated air atmosphere (all other leaves and the growing point having been excised), the HTO profile virtually ceases at a distance of 2 cm from the feeding chamber in the photosynthetic plant, but is greater and more extensive in the unilluminated plant. The differences are accentuated when roots are excised. Under these latter conditions the photosynthetic T-fixed gradient virtually disappears.HTO was exchanged with darkened petioles. When the rest of the shoot was kept in the light (the leaf being in a saturated H(2)O-vapor atmosphere) atmosphere) almost half the activity moves acropetally, and under these conditions (35 min, room temp) over 8% may be found in the leaf. Approximately one-tenth moves basipetally, with none being found in the stem. When the leaf is dark, no movement occurs out of the petiolar feeding chamber.An attempt was made to distinguish between sucrose transport by diffusion and mass flow of water by means of 2 mathematical models. In Model I, self-diffusion of HTO, Fick's Law was used, with the water and photosynthate moving independently. Model I consisted of an equilibrated, single pool of constant specific activity, generating a radioactive profile as a result of self-diffusion. In Model II, mass flow, water exchanged freely between the phloem and the surrounding tissues. The conducting bundle, 7790 micron(2), (0.25% of the total cross-section) was an average phloem. The numerical solution for the second model was obtained by Fortran programming on a digital computer and compared with experimental data. Comparison of these models with the experimental results suggest that mass flow is not a dominant process in soybean photosynthate translocation.
将 HTO 与大豆的气生部分进行交换的研究是在多种条件下进行的。当将 HTO 喂给饱和空气环境中的单个叶片或小叶（所有其他叶片和生长点均已切除）时，在光合作用植物中，HTO 谱在距供食室 2 厘米的距离处几乎停止，但在未受光照的植物中，HTO 谱更大且更广泛。当切除根时，这些差异会加剧。在这些后者的条件下，光合作用 T 固定梯度几乎消失。HTO 与黑暗的叶柄进行交换。当将其余的茎保持在光照下（叶片处于饱和 H(2)O 蒸汽环境中）时，几乎有一半的活性向顶运动，并且在这些条件下（35 分钟，室温），超过 8%的 HTO 可能在叶片中被发现。大约有十分之一的活性向基运动，而在茎中没有发现 HTO。当叶片黑暗时，不会从叶柄供食室中移出 HTO。尝试通过两种数学模型来区分蔗糖通过扩散和水的质量流动。在模型 I 中，使用 HTO 的自扩散，即 Fick 定律，水和光合作用产物独立移动。模型 I 由一个平衡的、具有恒定比活度的单一池组成，由于自扩散而产生放射性谱。在模型 II 中，质量流动，韧皮部和周围组织之间的水自由交换。导束，7790 微米(2)，（总横截面积的 0.25%）是平均韧皮部。第二个模型的数值解是通过在数字计算机上使用 Fortran 编程获得的，并与实验数据进行了比较。将这些模型与实验结果进行比较表明，质量流动不是大豆光合作用产物转运的主要过程。
