Characterization of senescence processes in attached flowers of Calendula officinalis L. and Aster novae belgii L

Experiments were carried out to characterise senescence processes in attached flowers of Calendula officinalis L. and Aster novae belgii L. As flowers open and finally senesce, petals show a striking colour change and wilting. Developing flowers of these plants growing in the university botanical garden were divided into four stages viz. half open, fully open, beyond open and advanced senescent stages. The average life span of these flowers from the half open to senescent stage was about seventeen days. Flower diameter and fresh weight of each scape showed a considerable rise between stage I and III followed by a decline in both plants. However, moisture content and membrane stability index exhibited a gradual decline from stage I to IV. Senescence in these flowers was accompanied by rise in petal malondialdehyde (MDA) content which enhanced lipid peroxidation and guaiacol peroxidase (GPOX) followed by the increment in free radical formation. Antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) play important roles in protecting petal tissue from peroxidation processes. Although activities of CAT and APX were very low at stage I, significant increment was noticed between stage I and III; followed by a sharp decline at stage IV. SOD was unique in having a moderate activity at stage I, registered gradual increment upto stage III and declined thereafter in petals of both plants. Both plants exhibited almost similar trends with respect to various physiological and biochemical changes investigated and compared in petal tissue. Petals from flower stage IV was characterised by low activity of SOD and significant reduction in APX and CAT activities, in comparison to preceding stage.