'n Ondersoek na die invloed van 8-hidroksikinoliensulfaat en n-6-bensielaminopurien op enkele aspekte van veroudering by angelierblomme

Abstract

The effect of N-6-benzylaminopurine (BAP), 8-hydroxyquinoline sulphate (HQS) and a BAP/HQS mixture on the display life and external appearance of cut carnation flowers (Dianthus caryophyl lus L. cultivar White Sim) was investigated. The effect of these substances on changes in water content, rate of respiration, total free amino acid content and concentration of the individual free amino acids in senescing petal tissue was examined as well. The rate of 14co2 production from a-alanine-u- 14c solution applied in presence of the preservatives, during incubation of petal and receptacle tissue, was determined. This was done to elucidate the effect of these preservatives on amino acid breakdown. Both BAP and HQS prolong the display life and have a beneficial effect on the appearance of the flowers. A higher water content is maintained in the petals, especially during the climacteric and post climacteric stages. The most efficient preservative is the BAP/HQS mixture. There are no noticeable changes in the pattern of respiration and the duration of the preclimacteric period in presence of the preservatives. The average rate of respiration in petals of BAP treated flowers is lower than that of untreated flowers. In the post climacteric stage, however, the rate of respiration in petals of BAP treated flowers exceeds that of untreated flowers. HQS as well as the BAP/HQS mixture increases the rate of respiration in the climacteric and post climacteric stages. All treatments result in the increase of the total amino acid level although to a lesser extent than in the petals of untreated flowers. The effect of the preservatives becomes more prominent in the post climacteric stage. BAP and the BAP/HQS mixture are more effective than HQS in decreasing the total free amino acid content.

The concentration of free threonine, serine, asparagine, glutamine, a-alanine, praline, glycine, methionine, phenylalanine, y-amino butyric acid and histidine are lower in petals of treated flowers than in the petals of control flowers. The differences in the concentration of these free amino acids are more pronounced in the post climacteric stage. The preservatives have little effect on the concentration of free aspartic acid, glutamic acid and lycine. They also inhibit the characteristic increase in the concentration of free praline and methionine as senescence progresses. HQS retards the decrease in water content and prevents the accumulation of praline, glutamine and asparagine under water stress conditions. The reduction of amino acid levels by the application of BAP is probably caused by the stimulation of protein synthesis and inhibition of proteolysis. The rate at which 14 co2 is produced from a-alanine-u- 14c in petal tissue is higher than in receptacle tissue. However, the preservatives decrease the rate of 14co2 production determined over a period of 24 hours. BAP seems to have a greater effect than HQS. The BAP/HQS mixture is the most effective of these preservatives in prolonging display life of cut carnation flowers by maintaining the moisture content of the petals and retarding protein and amino acid breakdown.