Toxic effects of a commonly used herbicide, 'taffacide' of the triazine group, have been evaluated in the root tip mitosis of maize, cv. Suwan. Germinated root tips were treated with three concentrations of the herbicide, viz. 5, 25 and 50 ppm for 6 and 12 h durations with two recovery periods for 4 and 8 h along with control. The root-tips were fixed in 3:1 alcohol-acetic acid fixative and examined cytologically through routine acetocarmine squash preparations. Marked mitotic depression was duration- and concentration-dependent. Reversal of adverse effects of the herbicide was observed during recovery treatments even in treatments with higher doses for longer durations (Table 1).

Various cytological abnormalities with varying frequency, viz. fragmentation, despiralization, C-mitosis, laggards, etc. were observed in 6 h treatment only, while giant cells and pulverisation were observed in 12 h treatments only. Maximum frequency of C-mitosis (0.69%) and fragmentation of chromosomes (0.78%) was scored in 50 ppm treatments for 6 h and recovery of 4 h.

Table 1. Effects of taffacide on root tip mitosis in maize.
 

Frequency of abnormalities (%)

 

Sl no.	Concn . (ppm)	Treatment (h)	Recovery period (h)	Mitotic index (%)	Total abnormal cells	Despiralization	Fragmentation	Stickiness	Pulverization	C-mitosis	Laggard	Binu. cell	Giant cells
1	5	6	4	9.22	2.28	1.54	0.33	-	-	0.42	-	-	-
2	5	6	8	10.23	2.09	1.48	-	0.30	-	0.31	-	-	-
3	5	12	4	4.36	0.70	-	-	-	-	-	-	-	0.70
4	5	12	8	5.52	0.55	-	-	-	-	-	-	-	0.55
5	25	6	4	7.21	3.08	2.13	0.45	-	-	0.50	-	-	-
6	25	6	8	9.19	3.47	2.38	-	0.53	-	0.39	0.17	-	-
7	25	12	4	3.39	0.97	-	-	-	-	-	-	-	0.97
8	25	12	8	4.47	0.97	-	-	-	0.39	-	-	-	0.58
9	50	6	4	5.91	5.87	3.75	0.83	0.55	-	0.69	-	-	-
10	50	6	8	5.88	5.16	2.60	-	0.84	-	0.35	-	1.37	-
11	50	12	4	2.09	1.19	-	-	-	-	-	-	-	1.19
12	50	12	8	3.35	1.20	-	-	-	0.47	-	-	-	0.73
13	control	-	-	10.54	-	-	-	-	-	-	-	-	-

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