RADIAL MOVEMENT OF C14-TRANSLOCATES FROM SQUASH PHLOEM,
Abstract
A time sequence study of the movement of C(14)assimilates at the tissue level was carried out with squash. Tissue of mature and immature petioles, stem, and hypocotyl were examined after 1-minute exposures of the primary leaf blade to C(14)O2. C(14)-Translocates were transported in the phloem from the mature leaf simultaneously toward the root and young organs of the upper plant. Rapid movement of the C(14)-front in the phloem was not due to gaseous diffusion of C(14)O2. Radial movement of C14-translocates occurred along the entire length of the phloem, ultimately supplying C(14) to every living cell of the plant within 2 hours of assimilation. The velocity and rate of radial movement depended on the stage of development of each plant organ. Young and rapidly expanding petioles displayed maximum velocities of about 6 cm/hour whereas older tissues showed velocities of about 1 cm/hour. These values compared favorably with those known for protoplasmic streaming but contrasted sharply with the velocity of C(14) conducted longitudinally in the phloem and estimated at between 250 to 300 cm/hour. Radial movement of C(14)-translocates appeared to occur in the form of sucrose rather than stachyose, which suggested a differential permeability of the conducting elements of the phloem toward these two sugars. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 23, 1964
- Accession Number
- AD0611618
Entities
People
- J. A. Webb
- P. R. Gorham
Organizations
- National Research Council Canada