The effect of low growth temperature on Hill reaction and Photosystem 1 activities in three biotypes of Kochia scoparia (L.) Schrad. with different sensitivity to atrazine and ALS-inhibiting herbicides

A possible influence of low growth temperature on the photochemical activity of isolated mesophyll chloroplasts was studied in three biotypes of kochia [Kochia scoparia (L.) Schrad.] that showed either double resistance to both atrazine and acetolactate synthase (ALS) inhibitors (Bubny biotype), resistance to ALS inhibitors but not to atrazine (Jihlava biotype), or sensitivity to both types of herbicides (Karlín biotype). Plants 5 or 12 weeks old since the date of sowing were examined. The Bubny biotype displayed the lowest values of Hill reaction activity (HRA) among all biotypes examined, and a significantly lower activity of Photosystem (PS) 1 compared to the Karlín biotype; this applied both for the control and low temperature-grown plants and for both plant ages studied. The comparison of HRA and PS1 activity in the Jihlava and Karlín biotypes showed lower values of both parameters for the Jihlava biotype. The HRA of plants grown at low temperature conditions was usually only slightly lower compared to the control plants of all three biotypes examined. The activity of PS1 in the kochia biotypes grown under low-temperature conditions increased markedly and significantly compared to the control plants; this increase was slightly higher in the atrazine-sensitive biotypes Jihlava and Karlín than in the resistant biotype Bubny. The differences between resistant and susceptible biotypes in the HRA diminished under low-temperature conditions whereas the differences in PS1 activity increased.