Weedy amaranth species usually have prolonged seed dormancy. Seeds of A. blitoides , A. gracizans , and A. retroflexus germinated after six years of burial. C. Germination 1. NOT due to lack of water uptake. Probably due to mechanical constraints or limited O2 diffusion.
Most species produce light-responsive seeds and germination is under phytochrome control.
Prolonged illumination usually inhibits germination at low temps. Germination increases as temps increase. Best emergence in field occurs in range of 24-34 degrees C. 4. Depth of emergence a. Small seeds and limited food reserves limits emergence depths.