CHLOROPHYLL, PROTEIN, AND NUCLEIC ACID LEVELS IN DETACHED, SENESCING WHEAT LEAVES

Abstract

Excised primary leaves of Little Club and Khapli wheats were allowed to senesce on water or on kinetin (10 mg/l.) for 6 to 8 days. Histological sections taken at 2-day intervals were stained for RNA, DNA, histone, and total protein. Twenty-five or thirty leaves were analyzed daily for chlorophyll, protein, and nucleic acids. Oxygen uptake was also measured. Examination of the sections showed that leaves senescing on water underwent rapid losses in chloroplast RNA and protein and in nuclear RNA. Losses in DNA, histone, and total nuclear protein were delayed until the nuclei disintegrated. These observations are correlated with the analytical results. The latter revealed statistically significant losses in chlorophyll, protein, and nucleic acid contents with time. The losses in nucleic acids were due mainly, if not entirely, to losses in RNA. Oxygen uptake per gram fresh weight in the leaves on water did not change significantly with days after excision. Kinetin significantly delayed losses in chlorophyll, RNA, and protein, and depressed oxygen uptake. Certain differences between the two varieties of wheat are described, including the more rapid loss of nucleic acid in Khapli.