Infection with phloem limited Abutilon mosaic virus causes localized carbohydrate accumulation in leaves of Abutilon striatum: Relationships to symptom development and effects on chlorophyll fluorescence quenching during photosynthetic induction

Infection with phloem limited Abutilon Mosaic Virus caused localized carboh ydrate accumulation (high levels of starch, sucrose, and hexoses) in leaves of Abutilon striatum during early symptom development. In mature leaves wi th attenuated symptoms, tissues showing faint vein-clearing had markedly hi gher carbohydrate contents than uniformly green areas of the same leaf. A s imilar pattern of carbohydrate accumulation was found in pale-green mosaics in mature leaves with overt symptoms when compared to green-islands of the same leaf, but overnight carbohydrate loses were comparable to controls. B ecause leaves with attenuated symptoms showed no further symptom developmen t whereas the pale-green mosaics became yellow and eventually necrotic in l eaves with overt symptoms, it seems unlikely that carbohydrate accumulation following impaired translocation was responsible for symptom expression. H igh carbohydrate status in leaves with attenuated symptoms had little effec t on nonphotochemical quenching during early stages of photosynthetic induc tion. In leaves with overt symptoms, areas of high carbohydrate status with pale-green mosaics showed markedly slower nonphotochemical quenching. Earl y symptom areas of young leaves, and advanced symptom areas of mature leave s had low starch contents but were otherwise similar to controls in carbohy drate status. Impaired nonphotochemical quenching in these tissues tended t o reflect the state of symptom development, Father than carbohydrate status . Plants with overt symptoms grew about half as fast as plants with attenua ted symptoms.