Identify the CORRECT combination of statements with respect to chemical defense in plants.
P. Pisatin, a phytoalexin produced by Ricinus communis is a constitutive defense compound
Q. Phaseolus vulgaris produces Phaseolus agglutinin I, which is toxic to the cowpea weevil
R. A single step non-enzymatic hydrolysis of cyanogenic glycoside releases the toxic hydrocyanic acid (HCN) to protect plant against herbivores and pathogens
S. Avenacin, a triterpenoid saponin from oat prevents infection by Gaeumannomyces graminis, a major pathogen of cereal roots