Characterization of the impact of wheat stem sawfly, Cephus cinctus Norton, on pigment composition and photosystem II photochemistry of wheat heads

Impact of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), feeding injury on chlorophyll content and photosystem H (PSII) photochemistry in heads of wheat, Triticum aestivum L., at the grain-filling developmental stage was evaluated by biochemically assessing the total chlorophyll, chlorophyll a (Chla), chlorophyll b (Chlb), chlorophyll a/b ratio (Chla/b), and carotenoid concentrations in the glumes in combination with a chlorophyll a fluorescence test. C. cinctus-infested stems had altered head glume pigment composition and photochemistry. Chlorophyll content, Chla, Chlb, Chla/b, and total chlorophyll, and the photochemical efficiency of PSII were greater for glumes of heads developing on infested stems. Chlorophyll a fluorescence was also affected by C. cinctus. In this study, wheat plants in a controlled environment were able to compensate for injury imposed by C. cinctus. The mechanism underlying the compensatory processes seems to involve the alteration of wheat head physiology. Based on our results, either the photochemical efficiency of heads on infested stems was greatly improved or their senescence was delayed.