EFFECT OF HERBICIDE GLYPHOSATE ON POLLEN GERMINATION IN VITRO AND POLLEN TUBE LENGTH OF Hibiscus cannabinus Linn

The germination of pollen grains in various concentrations of herbicide by adopting "Hanging drop technique" (Vasil, 1960). Effect of herbicide on pollen germination and pollen tube length was studied. Glyphosate inhibited the pollen germination and pollen tube growth at higher concentrations. The percentage of pollen germination was decreased from 29.29, 23.74, 11.49, 3.94 and 0.0 at 20, 40, 60, 80 and 100 ppm of glyphosate, respectively. Similarly, the pollen tube length was also declined and which was recorded from 373.7, 212.1, 80.8, 40.4 and 0.0 microns of Glyphosate at 20, 40, 60, 80 and 100 ppm of glyphosate, respectively. The bursting of pollen tubes at their tips were observed at higher concentrations of the herbicide.


INTRODUCTION
The pollen grains have been reported to be most sensitive to herbicidal action.The present investigation deals with the effect of glyphosate on pollen tube length and percentage of pollen germination in different formulation of herbicide.
Stock solution of 1000 ppm of Glyphosate were prepared by using tap water.Anther was collected from the weeds growing in fields.Pollen grains were collected on a cavity slide by taping the anther.The "Hanging drop" technique (Vasil 1960) was adopted for pollen germination and pollen tube growth experiment.The germination percentage of pollen grains and pollen tube length were calculated with respective concentrations of freshly prepared aqueous solution.The germination of pollen grains and pollen tube growth at different solution was studied from morning 7'O Clock onwards.

RESULTS AND DISCUSSION
The germination percentage of pollen grains and pollen tube length of H. cannabinus in tap water were 38.34 with 464.6 microns and 32.31 in distilled water with 300 microns, respectively.In sucrose solution it was 11.0, 19.5, 21.8, 35.52 and 25.2 at 100, 200, 300, 400 and 500 ppm with pollen  The germination percentage at 20, 40, 60, 80 and 100 ppm was 29.29, 37.74, 11.49, 3.94 and 0.0 and the pollen tube length was 373.7, 212.1, 80.8, 40.4 and 0.0 micros, respectively.The step fall in the percentage of pollen germination was observed at 20 to 80 ppm and at 100 ppm it was zero.Similarly, the steep fall in the pollen tube length was observed in the same concentrations as compared to control.Percentage of pollen germination and pollen tube length were decreased with increase in the concentrations of herbicide (Table -1 The bursting of pollen tube at there tips occurred in medium but maximum bursting occurred at higher concentrations of glyphosate.Abnormality like curvature of pollen tube was also occurred at higher concentrations of this herbicide.

DISCUSSION
In the present investigation, the percentage of pollen germination was found to be maximum in tap water as compared to distilled water and different concentrations of sucrose solution.Therefore, tap water considered as control media for further investigation.It was observed that drop of alcohol present in water did not change the percentage of pollen germination and growth of the pollen tube.
The pollen germination was maximum in control i.e. in tap water.Banerji and Ganguli (1937) in Eichhornia crassipes reported maximum pollen germination in tap water.Similar observations were recorded by Srinivasu (1987) in Parthenium
It was cleared that the percentage of pollen germination was zero at 100 ppm.So this concentration considered to be lethal dose.Workers like Jain (1993) in Chenopodium album, Bobde (1993) in Crotolaria juncea and Kulkarni (1998) in Crotolaria medicaginea var.Luxurians reported reduction of percentage of pollen germination due to application of glyphosate.
In present study, pollen tube length also decreased as the concentrations of glyphosate increased.It was 464.6, 373.7, 212.1, 80.8, 40.4 and 0.0 microns at control, 20, 40, 60, 80 and 100 ppm, respectively.An abnormalities like bursting of pollen tubes were occurred due to application of glyphosate.Similar results were observed by Bobde (1993) in Crotolaria juncea Jain (1993) in Chenopodium album and Kulkarni (1998) in Crotolaria medicaginea var.Luxurians.This herbicide inhibited the percentage of pollen germination and decreased the pollen tube length.From foregoing discussion, it was concluded that glyphosate inhibit the pollen tube growth with bursting which enhance the change of fertilization by revealing the moments of pollen tube through the stigma and style.

Table - 1: Effect of herbicide on pollen germination in vitro and pollen tube length and various concentrations of medium and glyphosate Medium / Conc. Total no. of Total no. of % of Pollen tube Abnormal Time / herbicide (ppm) pollen
R.B. -Rare bursting, F.B. -Few bursting, M.B. -Maximum bursting, Ab.Al. -Absolute alcohol