TRANSLOCATION OF NEWLY-ASSIMILATED CARBON IN THE VEGETATIVE SHOOT OF OLIVE

Measurements of phloem transport within vegetative shoots of three-year old olive (Olea europaea L.) plants grown in containers were made using ¹¹CO₂. The short-lived ¹¹C isotope has a half-life of 20.4 min and allows in vivo monitoring of newly-assimilated carbon.
Fully-expanded leaves differing in their position along the shoot (node 1, 2, 3 and 4 from the apex) were pulse-labelled with ¹¹CO₂ in an assimilation cuvette connected to a semi-closed gas exchange system at 25 °C, photosynthetically active radiation at 400 μmol m^-2 s^-1, and CO₂ of 380 μl l^-1. Labelling started about 4 h after the beginning of the photoperiod and leaves were actively photosynthesizing.
There were clear differences in the patterns of export out of the labelled leaf depending on leaf position.
No evidence of short-term export was found when the youngest fully-expanded leaf was labelled.
Labelling the second youngest leaf resulted in a strong tracer pulse in the portion of the stem immediately proximal to the petiole of the labelled leaf, but no activity a further 5 cm below; only a very small amount of radioactivity was detected in the acropetal direction.
When the 4th youngest leaf was labelled, the radioactive signal was strong in both detectors placed basipetally, but not in the acropetal direction.
Flows of newly-assimilated carbon showed typical diurnal courses, with an increase in the exported radioactivity in the afternoon (12 h after the beginning of the photoperiod).

IV International Symposium on Olive Growing

R. Gucci, P.E.H. Minchin

Carbon transport, Olea europaea, radioactivity, vegetative shoot.

https://doi.org/10.17660/ActaHortic.2002.586.95