Effect of spray application of 2 , 4-D on morphological characters of Hibiscus cannabinus Linn

In present study, the herbicidal activities of 2,4-D on Hibiscus cannabinus Linn. studied. The plants were sprayed with aqueous solution of different concentrations of 2,4-D from 100 to 5000 ppm. 2,4-D at all concentrations showed the effects like epinastically curvature, swollen and bending of stem. The leaves turned yellowish and roots became swollen and finally decayed. Vegetative growth of plants was retarded and finally plants dried. The lethal dose of 2,4-D was 500 ppm.


INTRODUCTION
Hibiscus cannabinus L. belongs to the family Malvaceae.Commonly known as Bimli, Bimlipatum, Jute and Deccan hemp in different regions of the country.Traditionally cultivated for cordage uses in Africa and Asia, some kenaf is used by small pulp mills primarily in countries like China, India, and Thailand (although much of the acreage in the latter is devoted to roselle (H.sabdariffa L. var.altissma).Since the 1960's, there has been increasing interest in kenaf as an annually renewable source of fiber for the manufacture of newsprint and other pulp and paper products in the United States and other countries.
Plants of Hibiscus cannabinus Linn.were raised from seeds collected from naturally growing plants of different places in Nagpur and its environs.They were allowed to grow till they attained the flowering and at this stage plants were plants were sprayed with different concentrations of 2,4-D.
The aqueous solution of herbicide ranging from 100 to 5000 ppm was prepared.Ten pots for each concentrations (100 to 2000 ppm) containing 2 to 3 plants were sprayed.If 2000 ppm was found higher; the lower concentrations were tried to determined lethal dose.Asppe-poly sprayer of one litter capacity did spraying.A small quantity of sodium lauryl sulphate as a surfactant added in the herbicide solution.The spraying was started in month of October 1996 and same experiments were repeated next year also.Spraying was done twice in an hour to make it more effective in the evening hour, when the wind was slow and temperature comparatively lower than that of the day.This help in less evaporation and more absorption of herbicide solution by the leaves.To avoid contamination of different concentrations of herbicide, cardboard was used at the time of spraying application.Six pots were sprayed with water used as control.Field trials were conducted on naturally growing plants in randomly designed plots of size approximately 3 :3 feet's.
The fresh and dry weight of shoots and roots of control as well as treated plants were taken to determined desiccation of plants.Morphological changes were observed daily till the death of plants.

RESULTS
The control plant of Hibiscus cannabinus Linn.were growing luxuriantly in the field as well as in earthen pots (Fig. 1c and 2).This herbicide showed some morphological changes at all concentration i.e. from 100 to 500 ppm after spray treatment.The growth of plants was inhibited as compared to control due to the application of herbicide.The plants treated with 2,4-D started showing some morphological changes after 48 hours of treatment.The epinastically curvature of stem, petiole, and chlorosis, necrosis on leaves were observed progressively at all the concentrations (Fig. 3 and 4 ).The curvature of the stems at apical nodes was maximum at 300, 400 and 500 ppm.The growing points of the plants were turned downwards.On fifth day, after application of herbicide the leaves at 400 and 500 ppm showed marked chlorosis (Fig. 3) as well as necrosis (Fig. 5).On sixth day, crumpling of leaves observed and leaves rolled inward and then started drying from margin towards midrib at all concentrations of herbicide (Fig. 6).On seventh day, chlorosis of leaves increased with increases in the concentrations and latter became yellow and ultimately leaves dried off.Owing to this, the lateral and apical vegetative growth of plants was inhibited.On eight day, stem and petiole turned yellow and latter on brownish spots occurred on petiole.Petiole rolled inward at 200, 300, 400 and 500 ppm (Fig. 7).On ninth day, nearly 100 percent of the leaves dried at 500 ppm.The stem, petiole, leaves, root dried completely, and death of plants occurred.Root showed formation of bulb like nodules around it (Fig. 8 and 9).Therefore, this dose was considered as a lethal (Fig. 1 and 10).Similar results were also observed in field trials (Fig. 11).
The vegetative growth stopped with injury to the plant apices and flowering inhibited in treated plants at all concentrations of herbicide.The plants appeared to be frozen due to inhibition of growth.In the next 5 to 6 days, the plants sprayed with 100 to 500 ppm concentrations of herbicide also dried.Fresh and dry weight of shoots and roots of treated and untreated plants were noted (Table 1).
Fresh weight decreased in both shoot and roots as the concentrations of herbicide increased from 100 to 500 ppm.At the same concentrations decrease was found in dry weight also (Table 1).

DISCUSSION
This herbicide found to be effective by inducing growth malformation, the epinastically curvature of stems and petioles at all concentrations.Epinastically curvature was occurred due to the unequal elongation of cortical cells and it has been supported by Zimmerman (1942) and Marth and Mitchell (1944) on Datura, Beal (1944b)  The inhibition of apical shoots appeared stunted growth till the death of plants progressively observed at all concentrations of herbicide.It has been reported by Weaver (1946) on bean spp.That 2,4-D was effective and it checked the height.Kelly (1949) on bean reported stunted growth of plants due to 2,4-D treatment.Khosla (1967) on Achyranthes aspera, Cassia tora, and Ruellia tuberosa reported vegetative growth inhibition due to application of 2,4-D.Bakale (1976Bakale ( , 1978aBakale ( , and 1978b) ) on Cress crecita, Alternanthera, Polygonoides var.erecta and Xanthium strumarium, reported inhibition of lateral and apical growth of stem.Raj and Tripathi (1986) on Galinsaga ciliata, and Galinsaga parriflora reported inhibition of growth.Srinivasu (1986) on Parthenium hysterophorus reported inhibition of apical and lateral shoots.Dhanpal et al. (1989) observed the growth of several weeds reduced by 2,4-D.Kasera and Sen (1990) on Chenopodium album, Chenopodium murale and Plantago ovate reported reduction of growth within few hours after applications of different concentrations of herbicide.Tripathi et.al. (1992) noticed stunted of stem growth in Lantana abcamera application of 2,4-D.Jain (1993) on Chenopodium album, Gopal (1993) on Medicago sativa and Bobde (1993) on Crotolaria juncea reported inhibition of shoots growth of these plants due to spray application 2,4-D.Suresh babu and Muniyappa (1994)  The flowers on the inflorescences dried and fell down at higher concentrations of 2,4-D were observed in the present study.Mitchell and Brown (1945) on Morning glory reported that new flowers failed to develop due to 2,4-D treatment.Khosla (1967) on Cassia tora, and Ruellia tuberosa, reported delaying in flowering and fruiting.Pearse (1970) on Homeria spp.noticed that 2,4-D prevented flowering in the weed.Bakale (1976) on Cress