INCREASED LEVELS OF CALCIUM IN THE NUTRIENT SOLUTION IMPROVES POST HARVEST LIFE OF POTTED ROSES

Uptake of Ca is considered to be passive, but it can be depressed by competition with other cations.
We conducted experiments on miniature pot roses to find whether increasing the Ca content of the nutrient solution affected Ca content in the plant and thus improved postharvest quality.
The pot rose cultivar ‘Poulprima^N’ (Purple Parade®) was grown in kiln dried clay particles having a low cation exchange capacity and a very low nutrient content growing medium (Seramis®). The six treatments used six different nutrient solutions having varying meq ratios between Ca and total cations.

Graphic available in full text only

At harvest, Ca contents of the flower, stem, leaf and root (Figures 1A, 1B, 1C, 1D) all increased significantly with increasing Ca/cation ratio in the nutrient solution.
Ca content in stems and leaves showed no interaction between Ca and NH₄ levels in the nutrient.
There was a higher Ca content in flowers and buds with high NH₄, while it was generally lower in the roots.
At harvest, the highest Ca treatment had significantly fewer flowers than all other treatments.
During day 0 to day 14 of postharvest storage, the number of good flowers increased irrespective of treatment.
The two highest Ca treatments (5 and 6) maintained their keeping quality longest.
Keeping quality declined most rapidly in the lowest Ca treatment.
Grey mould infection was negatively correlated with Ca content in the flowers.

Flower wilting resulted from a physiological process which started at the petal edges as a dark discoloration, and infection with grey mould.
The physiological wilting was seen earliest in the treatments with high NH₄, and is probably not related to the Ca content in the flowers.
The effect of NH₄ could either result from a lowering of carbohydrate reserves in the plants leading to an earlier depletion during postharvest, or indirectly through a decrease in medium pH during growth leading to damage of the roots.
High Ca content may have reduced grey mould infection by delaying senescence of the tissues.
Thus we conclude that (1), Ca uptake was positively correlated with Ca/cation meq ratio in the nutrient solution; (2), high Ca content increased the postharvest quality and reduced grey mould infection; (3), NH₄ had a negative effect on the longevity of the flowers.

International Postharvest Science Conference Postharvest 96

K. Rasmussen, A. Pedersen, C. Ottosen

https://doi.org/10.17660/ActaHortic.1998.464.126