. Peroxidase (PO)
Peroxidases is a multipurpose stress sensitive enzyme (Thakker et al., 2013) that catalyses the oxidation of variety of substrates, mainly hydrogen peroxide (H2O2). The H2O2-dependent reaction catalyzed by Peroxidases results into the condensation of phenolics to lignins (Thakker et al., 2013), thereby removing the toxic H2O2 from tissues (Lebeda et al., 1999).

The key function of PO is lignin biosynthesis (Bruce & West, 1989) in plants. Lignins add strength to the cell wall creating physical barriers against the pathogen in the host tissue (Almargro et al., 2009; Thakker et al., 2013). The enzyme is also involved in deposition of phenolic compounds into cell wall during resistance in plants (Graham & Graham, 1991) thereby related with plant …show more content…
Activation of phenylpropanoid metabolism is one of the key reactions for disease resistance in several plants (Dixon & Palva, 1995). The PAL catalyzed reaction involves the substrate phenylalanine that undergoes deamination to yield transcinnamic acid and ammonia (Fraser & Chapple, 2011). Trans-cinnamate is the precursor of several phenylpropanoid derivatives. Some of them include lignins, anthocyanins, antipathogenic, phytoalexins, antioxidants, UV-absorbing compounds and signal molecules (Whetten & Sederoff, 1995; Holton & Cornish, 1995; Weisshaar & Jenkins, 1998; Raju et al., 2008). The enzyme is extensively studied because of its role in defense response leading to disease resistance in plant species. The elicitor induced increased accumulation of PAL activity was studied in Solanum (Bariya et al., 2011), barley cell suspension (Peltonen et al., 1997), alfalfa (Fahrendorf et al., 1995), tobacco (Muhlenbeck et al., 1996), soybean (Borejsza-Wysocki et al., 1999) and dioscorea (Li et al.,