Effects of sublethal herbicides on offspring germination and seedling growth: Redroot pigweed (Amaranthus retroflexus) vs. velvetleaf (Abutilon theophrasti).

The effects of sublethal doses of herbicides on plants cannot be ignored, yet little is known about the effects of sublethal doses of herbicides on the F1 generation of plants. Seed germination and seedling growth of native and invasive plants following the sublethal exposure of parent plants to herbicides were comparatively analyzed in this study. Sublethal atrazine and tribenuron-methyl had carry-over effects on the germination and seedling growth of the F1 generation of invasive redroot pigweed (Amaranthus retroflexus L.) and native velvetleaf (Abutilon theophrasti Medicus), both of which had different responses to the carry-over effects of sublethal herbicide. The germination percentage of the F1 redroot pigweed (decreased) was greater than that of the F1 velvetleaf (increased or not significantly changed) following parental exposure to atrazine or tribenuron-methyl. Atrazine reduced the radical growth of 7-day-old velvetleaf seedlings and decreased the difference in seedling length between velvetleaf and redroot pigweed, while tribenuron-methyl had no significant effects on the growth of 7-day-old velvetleaf seedlings. The herbicide inhibition effect on the germination and growth of F1 velvetleaf and redroot pigweed did not increase as the sublethal dose increased. This study suggests that carry-over effects of sublethal herbicides weaken the growth advantage of the F1 velvetleaf at the seedling stage and may have a more negative influence on progeny population development of native velvetleaf compared with invasive redroot pigweed.