The influence of Peronospora tabacina Adam upon the growth rhythm of Nicotiana tabacum cv. Samsun.

The cinematographic method was used for studying the changes of the growth rhythm of the leaves in Nicotiana tabacum cv. Samsun after the inoculation with Peronospora tabacina Adam. The leaves were screened only at the maturing phase when displaying characteristic disturbances of the growth rhythm. The leaves of a healthy plant show a regular growth rhythm, with regular amplitudes of growth spirals and growth rate. The growth spiral increments are elongated regular and even up to the mature stage of the leaf. In Nicotiana tabacum cv. Samsun the original regular rhythm was kept for 130 hrs. after the infection with the conidia of Peronospora tabacina Adam. When the first symptoms of the disease appeared on an inoculated leaf (approximately after 20 hrs.), fructification of the mould occurred, the growth rhythm was retarded and, after the necrotization of spots, the leaf died away.