Physiological effect of the toxin from Xanthomonas retroflexus on redroot pigweed (Amaranthus retroflexus)

A new toxin from Xanthomonas retroflexus could cause a series of physiological responses on seedlings of redroot pigweed. The experimental results revealed that respiratory ratio first increased 106% after treatment with the CFS (concentrated centrifugal fermentation supernatants) of X.retroflexus for 2 h, and decreased after treatment for 3 h; peroxidase (POD) activity increased 30% and 50% after treatment with CFS for 1 h and 2 h, respectively; Malon dialdehyde (MDA), soluble protein andmitotic indices appeared not to be affected by the toxin. Ultrastructure observation indicated that the thylakoids of chloroplast and cristae of mitochondria swelled, when the leaves were placed in the toxinfor 2 h. After treatment with the phototoxin for 3 h, the cell membrane was disrupted, the chloroplasts disintegrated and the mitochondria vesiculated