Estimation of the sensitivity to photoinhibition in Striga hermonthica-infected sorghum |
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Authors: | Ramlan, M.F. Graves, J.D. |
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Abstract: | Sensitivity to photoinhibition was assessed in sorghum infectedwith the angiosperm root parasite Striga her-monthica and inuninfected sorghum plants, at four times during the developmentof the host-parasite association. Photoinhibition was inducedby exposing either leaf discs or intact leaves to a photosyntheticphoton flux density of 2000 µmol m2 s1 for4 h. The inhibition of apparent quantum yield (a) and photosynthesisin high light (A1500) were assessed in leaf discs using an oxygenelectrode and the recovery of these from photoinhibition wasfollowed in intact leaves using an infra-red gas analyser. Fromsoon after attachment of the parasite, infected sorghum plantshad a lower A1500. During the period when Striga induced a loweringof A1500, a was more sensitive to photoinhibition in Striga-infectedplants. However, at the same time, the high-light-induced inhibitionof A1500 was similar in Striga-infected and uninfected plants.Recovery of both a and A1500 was incomplete after 6 h and thetime-course of recovery was similar in Striga-infected and uninfectedplants. The results indicate that Striga-infected plants weremore sensitive to photoinhibition and that photoinhibition wasprimarily due to damage to electron transport/photo-phosphorylationand not disablement of the recovery processes. Key words: Photoinhibition, quantum yield, recovery from photoinhibition, parasitic plants |
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