An Analysis of Translocation in the Phloem of the Bean Plant Using Tho, P³², And C¹⁴.

Time-course Study of Translocation of Products of Photosynthesis in Soybean Plants

“…Logarithmic gradients of translocated radioactivity in stems have been noted by others (1,9,10) and attempts have been made to interpret them in relation to velocity or rate of translocation or to concurrent losses from the sieve tubes to the surrounding tissues (1,2,3,4). In all cases but one (9), these gradients have been observed in short-term experiments.…”

“…In all cases but one (9), these gradients have been observed in short-term experiments. Only 2 reports (1,10) have noted the changes in gradient characteristics that occur when the duration of C14-assimilation and translocation is increased, and in these the experiments were limited to periods from 5 to 30 minutes. Kursanov and Pristupa (5,6,8) have recently reported evidence in support of the classical concept of a circulation of carbon compounds from the leaves to the roots and back to the tops with metabolism in the roots playing an important role in the overall process.…”

Phosphorus Compounds in Translocating Phloem

“…The only consistent effects were an increase with time in the proportion of radioactivity in UDPglucose and in material fixed near the origin (mainly RNA), and a decrease with time in the proportion of radioactivity in nucleotide triphosphate and in Pi (table IV). (2). The improvements which were made-study of vascular tissue alone rather than the whole petiole, use of better extraction and chromatographic proceduires, and a search for a gradient in ester pattern along the petiole-were expected to yield more definitive information, and so the results are rather disappointing.…”

Some Simplified Mathematical Treatments of Translocation in Plants.

“…But, data from tracer studies have lately been appearing in the literature which permit a much more quantitative evaluation of the translocation process than had previously been possible. The main feature of these data is that there is generally a more or less linear relationship between the logarithm of the radioactivity at any place in the stem and its distance from the region of application (1,2,3). In this paper the consequences of a number of simple theories of translocation have been derived mathematically, in order to see which of these theories are plausible and conform to experimental observations.…”

“…The force tion is modified to actuating this cycle is the turgor pressure of the chlorenchyma of the leaf, which, in the simple theory, (42) must be sufficient to do the following: 1) push the flowing liquid through the plasmodesmata, sieve tubes, from the pipe at a and sieve plates constituting the translocation column; ,ion by an enzyme 2) exert a turgor pressure on the inside of the memiay occur when the branes of the sugar consuming cells sufficiently greater l uniformly active than the equilibrium osmotic pressure of these cells so nuity equation be-that water is forced out against the osmotic gradient at a rate necessary to account for the flow rate in the phloem; 3) push an amount of water up through the If -q = -1 and if we assume that )= 100 (7), then the diffusion constant is effectively increased by a factor of about 5,000; if q = 10w, then the diffusion constant is effectively increased by about 9,000 times. 3 The mechanism just discussed depends on ordinary diffusion processes subject to Fick's laws (12). However, if use is made of a system that preferentially allows diffusion in one direction, then even further increases in the rate of transfer can be imagined.…”