Articles
THE ROLE OF ENZYMES DURING SENESCENCE OF CUT FLOWERS
Each of these phases of plant development is associated with distinctly different functions of the cells and with the formation of different biochemical pathways in living organisms.
This results in the formation or activation of various new enzymes or whole enzymatic systems in appropriate phases of plant development.
Experiments performed by Hedley and Stoddart (1971, 1972) on the incorporation of 14C-aminoacids into proteins support this opinion.
Concerning post-harvest physiology of cut flowers, the greatest deal of attention is devoted to senescence processes.
These usually occur very quickly because flowers are composed of many organs, and are not adapted to long-term survival separate from the mother plant.
Small amounts of energy sources and the lack of a cuticle preventing fast transpiration, also diminish the period of cut flower vase-life.
On the other hand, however, it is hard to imagine that plant organisms excellently prepared for growth and developmental processes would not have the ability to control the senescence of their organs.
The data presented by Hobson and Nichols (1977) indicate that the phase of total wilting of carnation petals is preceded by the accumulation of protein in them.
These data as well as results from the electrophoretic separation of protein molecules, support the idea about the synthesis of new enzymes, and the degradation of some groups of extant enzymes during the senescence of petal tissues.
Thus, it seems obvious that this synthesis is not incidental, but that it is programmed into the genetic material of the cell.
Experiments performed by Yoshida (1961) have shown that mesophyll cells of Elodea containing a nucleus tended to decay very quickly after treatment with CaCl2. Nucleus-free cells treated in a similar way remained green and continued to synthesize starch for the next 5 days after treatment.
These observations support the idea that the control of the senescence mechanism is located in the nucleus.
Another example illustrating the genetic control of the senescence process is the chlorophyll degradation in wilting leaves of Festuca pratensis.
This species has a mutant in which the leaves do not turn yellow (Thomas and Stoddart, 1975), and in which the inheritance of this specific feature follows Mendel’s laws.
This can be explained by the fact that the genes responsible for chlorophyll degradation are localized in the cell nucleus.
In most cases so far observed, the petals are the flower organ which determines the period of life of cut flowers.
It is obvious that the wilting of petals simultaneously results in diminishing the decorative value of the whole flower.
Therefore, much attention has been given to the biochemical processes taking place in flower petals.
Nevertheless, despite a great number of investigations devoted to the biochemical basis of wilting (Halevy and Mayak, 1979), our knowledge of this phenomenon