ISHS Acta Horticulturae 239: VI International Symposium on Growth Regulators in Fruit Production
LOCALIZATION OF CALCIUM WITHIN CELLS OF THE ABSCISSION LAYER OF LEMON LEAF EXPLANTS |
| Authors: | S. Iwahori, R.F.M. Van Steveninck |
| Abstract:
Abscission of citrus leaf explants is delayed by calcium and accelerated by trifluoperazine (TFP), an inhibitor of calcium-calmodulin dependent processes. Electron probe X-ray microanalysis of quench-frozen lemon leaf explants was used to monitor changes in distribution of calcium in the cell walls and vacuoles of various tissues near the abscission layer during aging of the tissue. Results obtained from individual cells are variable, but generally in fresh samples high levels of calcium occurred in the vacuoles and especially the inner tangential walls of epidermal and sub-epidermal cells near the gap of the abscission zone. Elsewhere, levels of calcium were often below the limit of detection except in cell walls of the cortex, xylem and pith parenchyma cells. Calcium containing crystals (presumably calcium oxalate) were abundant in vacuoles of the cortex parenchyma away from the separation layer on both the petiolar and leaf blade sides. Calcium levels in cell walls and vacuoles usually declined after 2 days aging in water or TFP but were generally maintained in explants treated with IAA. | |
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