Ammonium and proline accumulation in senescing cut leaves of Zantedeschia

Accumulation of ammonium and proline were reported as phenomena associated with plant response to stress and/or senescence. The effects of a preservative (8HQC + sucrose) and 24 hrs pulse conditioning with GA₃ on the ammonium and proline contents were studied in senescing cut leaves of Zantedeschia aethiopica Spr. and Z. elliottiana Engl., grown for the florists green. Generally, accumulation of both compounds was observed in senescing leaves, however, the final ammonium and proline levels depended upon the species and the treatment applied. Conditioning with GA₃, a treatment known to delay leaf senescence in Zantedeschia sp., prevented the increases in the ammonium and proline contents. Standard preservative solution used to prolong the longevity of cut flowers enhanced the ammonium accumulation in senescing leaves of both species, and the proline accumulation in the leaves of Z. aethiopica, but not in Z. elliottiana. These observations suggest that neither ammonium nor proline accumulation would be fully reliable predictors of cut leaf freshness during their entire market life. However, proline accumulation could serve as a quick test of freshness in the first half of the useful market life of cut leaves of Zantedeschia.