PHOTOSYNTHETIC PROPERTIES OF LEAVES OF EUPATORIUM-MAKINOI INFECTED BYA GEMINIVIRUS

We examined photosynthetic properties of Eupatorium makinoi leaves inf ected by a geminivirus. Since a major symptom of the geminivirus infec tion is variegation or yellowing of leaves, Chi content was used as an index of disease severity. As leaf Chi content was lowered, leaf abso rptance, maximal quantum yield of photosynthesis on an absorbed quantu m basis (phi O-2,(max)) and light-saturated rate of photosynthesis (P- max) decreased. The share of energy allocated to PS II, which can be e stimated from fluorescence parameters and oxygen evolution rate, was a bout 30% lower in the infected yellow leaves than in uninfected leaves . Analyses of the composition of thylakoid polypeptides by gel electro phoresis showed preferential loss of LHC II. The lower phi O-2,(max) i n the infected leaves was, thus, attributed to the decreased energy al location to PS II. These features were largely consistent with those o f b-less mutants, but lowered P-max has been never reported for b-less mutants. Possible mechanisms causing these changes in photosynthetic properties to the infected leaves are discussed.