The laticifer system of Chamaesyce thymifolia: A closed host environment for plant trypanosomatids

Specimens of Chamaesyce thymifolia (Euphorbiaceae) infected and uninfected by Phytomonas sp., a parasite of the Trypanosomatidae family, were anatomic ally and ultrastructurally analyzed with special emphasis on the laticifer system. C. thymifolia presents branched non-articulated laticifers and was heavily infected by Phytomonas sp. in all collection sites. Infection was o ften observed in the initial stages inside the vacuole, when the latex part icles could be seen. In intermediary stages of laticifer differentiation, P hytomonas sp. were found free in the cytoplasm, inside small vacuoles or in the central vacuole. In differentiated laticifers that had only the plasma membrane, Phytomonas sp. were free in the latex and close to the cell memb rane. Infected and uninfected plants showed identical anatomy and ultrastru cture and the starch grain numbers in the latex were not reduced in the pre sence of this flagellate. Biochemical analysis of the latex of infected and uninfected plants presented similar levels of protein, carbohydrate and be ta-1,3-glucanase, suggesting that this species is not pathogenic for the ho st. Besides, all infected plants complete its life cycle. Plants infected w ith Phytomonas presented occasionally virus like particles and bacteria ins ide the laticifer tubes.