Effect of ozone on photosynthesis and seed yield of sensitive (S156) and resistant (R123) Phaseolus vulgaris L. genotypes in open-top chambers - Scheepers, C.; Strasser, R.; Kruger, G. (Suid-Afrikaans Tydskrif vir Natuurwetenskap en Tegnologie / South African Journal of Science and Technology, 2013)