Photosynthetic Responses of Soybean to Soybean Aphid (Homoptera: Aphididae) Injury

Physiological and Biochemical Responses of Resistant and Susceptible Wheat to Injury by Russian Wheat Aphid

“…Changes in trans-thylakoid pH might compromise synthesis of zeaxathin by the xanthophylls deepoxidase enzyme, which could lead to increased formation of triplet state chlorophyll and singlet state oxygen, thereby decreasing the efÞciency of photosynthesis (Malkin and Niyogi 2000). Our Þndings, which are similar to Macedo et al (2003a), indicate that chlorophyll may not be directly impacted by aphid injury but rather by biochemical mechanisms involved with quenching may be more immediately impacted by aphid feeding.…”

“…D. noxia did not have a signiÞcant impact on F v /F m , indicating that the antennal chlorophyll complexes and electron transfer to the reaction center of PSII was not impacted negatively by aphids. Macedo et al (2003a) also found that the soybean aphid, Aphis glycines Matsumura, regardless of aphid density, did not alter the photoelectron transport in soybean, Glycine max (L.) Merr. With sufÞcient time (i.e., experiments of longer duration), it is likely that photosystem injury can be associated with D. noxia infestation, but in this study we observed decreased photosynthetic activity without apparent changes in electron transport.…”

“…SigniÞcant changes in the quenching coefÞcients, especially in the susceptible cultivar, suggest that aphid feeding may inßuence the photoprotective xanthophyll cycle by altering the pH gradient across the thylakoid membrane (Macedo et al 2003a). Changes in trans-thylakoid pH might compromise synthesis of zeaxathin by the xanthophylls deepoxidase enzyme, which could lead to increased formation of triplet state chlorophyll and singlet state oxygen, thereby decreasing the efÞciency of photosynthesis (Malkin and Niyogi 2000).…”

“…Based upon these observations, it is evident that gas-exchange responses are a more sensitive physiological parameter than chlorophyll measurements. Moreover, it seems likely that altered chlorophyll levels may be a secondary effect and not the primary trigger of declined host plant function (Macedo et al 2003a). Previous studies on how aphids alter plant gas-exchange processes have indicated that photosynthetic inhibitions occur before CO 2 assimilation with rubisco (Ryan et al 1987, Haile et al 1999.…”

Chlorophyll Content of Aphid-Infested Seedling Leaves of Fifteen Maize Genotypes

“…In susceptible T. aestivum cultivars colonized by D. noxia, Burd and Elliott (1996) found elevated F o levels, which may disrupt electron transfer in the PSII system and reduce D1 protein synthesis. Soybean aphid feeding altered the quenching coefficients (qP, coefficient of photochemical fluorescence quenching; qN, coefficient of nonphotochemical fluorescence quenching) in tissues of infested soybean plants, according to Macedo et al (2003), who suggested that aphid colonization may suppress the xanthophyll cycle, which participates in protecting photosystem II under stress conditions by modulating the thylakoid membrane pH gradient. Haile and co-workers (1999) reported substantial reduction of photosynthetic efficiency in wheat plants attacked by D. noxia.…”