Effect of strontium on chlorophyll content, peroxidase activity, and iron distribution in cell walls

Phenolic and Oxidative Metabolism as Bioindicators of Nitrogen Deficiency in French Bean Plants (Phaseolus vulgaris L. cv. Strike)

“…The metabolism of phenolic compounds involves the activation of oxidative enzymes, such as PPO and POD, which catalyse the oxidation of phenols to quinones (Vaughn and Duke, 1981 [60] ; Thipyapong et al, 1995 [57] ). Numerous researchers have demonstrated the activity of both enzymes to be affected by different types of biotic and abiotic stress (McConchie et al, 1994 [35] ; Cheng and Crisoto, 1995 [15] ; Thipyapong et al, 1995 [57] ; Söderhäll, 1995 [52] ; Kwak et al, 1996 [30] ; Thipyapong and Stellens, 1997 [58] ), notable among the latter being the nutritional status of elements such as B and Ca (Kawai et al, 1995 [25] ; Söderhäll, 1995 [52] ; Kwak et al, 1996 [30] ; Cakmak and Römheld, 1997 [10] ; Tomasbarberan et al, 1997 [59] ; Kim and Heinrich, 1997 [29] ; Ruiz et al, 1998 [46] , 1999 [47] ). In our experiment, the N dosage significantly affected the activities of PPO and POD (p < 0.001; Table 1), N2 and especially N1 presenting the highest activities, while N3 gave the lowest, with a reduction of 42 and 58 %, respectively.…”

“…The enzymatic activities responsible for synthesis (PAL) and phenolic oxidation (PPO and POD) are regulated by many factors, both biotic and abiotic factors. For example, resistance-inducing biotic and abiotic factors (Smith-Becker et al, 1998 [51] ), pesticides and herbicides (Scarponi et al, 1992 [48] ; Molina et al, 1998 [37] ; Ruiz et al, 1999 [47] ), the nutritional status of certain nutrients (Cakmak and Römheld, 1997 [10] ; Ruiz et al, 1998 [46] , 1999 [47] ), Ca (Söderhäll, 1995 [52] ; Kawai et al, 1995 [25] ; Kim and Heinrich, 1997 [29] ; Tomasbarberan et al, 1997 [59] ), and different types of stress (Dixon and Paiva, 1995 [17] ) bring about major variations in phenolic metabolism.…”