The mechanism of kinetin-induced transport in corn leaves

Abstract

1. Kinetin-induced transport of P(32) in detached corn leaves is shown to be limited to the axial direction of the leaves, i.e. along the axis of the vascular bundles. It is not apparently dependent on the water flow in the xylem, and it can be blocked by steam-killed zones or by metabolic inhibitors. It is concluded that kinetin-induced redistribution of phosphates in isolated corn leaves takes place in the phloem. 2. The movement of P(32) is preferentially toward the base of the excised leaf, indicating a natural mobilization center at the leaf base. 3. Kinetin treated parts of leaves attract and accumulate P(32). They do not accumulate the radioisotopes Na(22), Rb(86), Cl(36) and I(131); but the transport of Na(22) directed towards kinetin centers is enhanced. 4. Two "mobilizing centers" established by kinetin application along the leaf axis do not attract P(32) from intermediate tissue at the same time in opposite directions. They compete with each other for the transport system: both the direction and the velocity of movement are determined by the difference of the "mobilizing forces". Thus, mobilization is either to one or to the other mobilizing center. 5. Under conditions of enhanced transport (i.e. in presence of kinetin centers), the distribution curves of P(32) and Na(22) are flattened. This change would be expected for the mass-flow type of transport. 6. It is concluded that "mobilizing centers" in isolated corn leaves stimulate a mass-flow transport in the phloem. Evidence is presented that they act as suction pumps. Some general aspects of phloem transport are discussed.

Growth Regulator Induced Movement of Photosynthetic Products Into Fruits of `Black Corinth' Grapes

“…Similar results have been obtained with detached corn (Zea mays L.) leaves (11,12) and detached Victorv oat (Avena sativa) leaves (3), by the use of radioactive glycine and 32p, respectively. Little such work has been done with flowers or fruits.…”

Effects of Growth Substances on the Absorption and Transport of Iron Plants

“…The growth promoters and retardants might exert their influence on the actively growing regions and help mobilize the nutrients absorbed elsewhere toward the shoot. Further studies with these chemicals on similar lines as reported for kinetin (17) would perhaps be more revealing.…”

“…Growth substances are known to increase, retard, or modify plant growth by affecting diverse metabolic processes (18,19), and it is likely that these substances also affect the mechanism of ion uptake (17). However, very little information relating to the action of growth substances on the absorption and transport of Fe is available in the literature (1,12,20).…”

“…The mechanism by which these chemicals of diverse nature act on the ion uptake process is not known. A possible explanation would lie in the "source and sink" theory (17), and the actively growing shoot region is assumed to be the "sink" area for ions. The growth promoters and retardants might exert their influence on the actively growing regions and help mobilize the nutrients absorbed elsewhere toward the shoot.…”

Effect of Sink Region Cooling on Translocation of Photosynthate

“…The temperature at this point showed short-term changes of less than 0.20 and could be held within ± 10 for at least 24 hours. The roots and lower part of the beet were mainlocate molecule arriving in the sink.The data suggest that the translocation anid growing areas.Ak number of mechasnisms have l)een propose(l for getneratinig the pressutre gra(lielnts postuilated in the pressuire-flow translocationi model (1,4,6,8,11,13,17). In this model system translocate is conceived as Imlovinig from a site of suipply (the source) to a place of utilization or storage (the sink).…”