Allelopathic effects of Cassia tora and Cassia uniflora on Parthenium hysterophorous L .

Laboratory studies on the seed powder and water extract of seeds of Cassia tora and Cassia uniflora on the germination of Parthenium seeds was studied. Seed powders of both weeds were much inhibitory on seed germination of Parthenium than the water extract. Seed powder of Cassia tora showed maximum germination inhibition of 98% and water extract of 67%, whereas seed powder of C. uniflora showed germination inhibition of 95% and water extract of 61%. The results showed that the C. tora seed powder and water extract of its seeds showed much inhibitory effect than C. uniflora on Parthenium.


INTRODUCTION
In plant protection, allelochemicals play a vital role.In floral community there is much influence at biodiversity and composition level.Allelochemicals vary at various stages of plant and also in different parts of plants, in particular stages of development.Out of many competitors, widely found Cassia species are widely distributed herbaceous weeds common in India wastelands.
Cassia tora and Cassia uniflora cover a large area of wastelands.Cassia species can be used for the biological control of Parthenium hysterophorus.Plant parts of C. tora have allelochemicals which inhibit seed germination of Parthenium (Kumar and Bhan, 1997;Senthil et al., 2004;Singh and Thapar, 2002).
Biochemical substances are mostly secondary metabolites by plant in primary metabolism intermediates pathway called allelochemicals.There are several ways in which allelopathic plants can release their protective chemicals which include volatilization, leaching, exudation, etc. (Akhtar et.al, 2001).
Of these various ways, weed-weed interaction is an important phenomenon which was observed in case of Cassia uniflora and Cassia tora dominates on Parthenium and Achyranthus aspera dominates on C. uniflora.
P. hysterophorous L. commonly called congress grass is a vigorous colonist in poor and overgrazed pastures and readily occupies bare areas where stock movement is frequent.It does not invade most well managed crops and pastures, but may be a problem even when present at low levels.Parthenium weed inhibits the growth and germination of other plants by allelopathy.
Parthenium weed is known to cause allergic reactions in people (Mahadevappa and Patil, 1999).Symptoms are itching on exposed skin and development of a dermatitis which may spread over the whole body.It also causes asthma.The sesquiterpene lactone parthenin is the major allergen produced.C. tora and C. uniflora were tested for antigermination activity by allopathic effect on P. hysterophorous L.

Collection of plant
The seeds of C. tora and C. uniflora were collected from pods from University of Pune campus.The seeds were obtained from pods, dried and then powdered for carrying out further experiments.
Parthenium plant was collected from University of Pune campus seeds which were obtained from these plants.The seeds were dried and powdered in a pestle and mortar.

Preparation of water extract
Water extract of seeds of C. tora and C. uniflora was prepared by distilling the seed powder with water in a Soxhlet distillation apparatus.

Apparatus used
Sterile petri plates, germination paper, Soxhlet distillation apparatus was used for the extraction of seed powder.

Preparation of seeds powder
The seeds of C. tora and C. uniflora were dried in the sun and powdered.

Preparation of water extract
Fifty grams of seed powder of each plant was taken in a round bottom flask containing 500 g of water and an extraction was carried out in a Soxhlet distillation apparatus for 8 h.The extract was then filtered and used for experimentation.

Germination test
Healthy and equal sized seeds of P. hysterophorous were taken in a beaker.The seeds were soaked in hot water (50 ml) up to 5 min.Out of these, 100 seeds were taken for germination test.Treated seeds are sown in petri plate containing germination paper and water extract was taken and petriplate was then kept in germination chamber at temperature of about (22 to30°C).
Similarly in control, seeds without water extract were taken with distilled water for 7 days.Both petri plates were kept in germination chamber for 7 days.Two laboratory germination tests were conducted at 25°C.

RESULTS AND DISCUSSION
The results of the experiment are tabulated as shown in Tables 1 to 4. The data on the seed powder and seed powder water extract of C. tora and C. uniflora on the germination of Parthenium seeds is as shown in Tables 1  to 4.
Seed powders of both weeds were much inhibitory on seed germination of Parthenium than the water extract.Seed powder of C. tora showed maximum germination inhibition of 98% and water extract of 67%, whereas seed powder of C. uniflora showed germination inhibition of 95% and water extract of 61%.The results showed that the C. tora seed powder and water extract of the seeds showed much inhibitory effect than C. uniflora.
It can also be concluded that allelochemicals extracted from C. tora and C. uniflora have the potential to inhibit the germination of Parthenium seeds.C. tora and C. uniflora showed allelopathic effect on Parthenium.Both plants are found in abundance in nature.By using water extract or simply seed powder, inhibition of Parthenium takes place which is confirmed by this experiment.
In water extract of the seeds and seed powder, some allelochemical substances are present which affect germination of Parthenium.In future, Cassia species can act as herbicide to other weed such as Parthenium.For agricultural practices, both are more beneficial, because they are abundant in nature and have high inhibition property to Parthenium.
The allelochemicals present in extract affected germination and seedling growth (Narwal et al., 1992).The allelochemicals present in extract might have altered some of the physiological processes responsible for the plant growth.

Table 1 .
Germination of Parthenium hysterophorous seeds exposed to Cassia tora seeds powder.

Table 3 .
Germination of Parthenium seeds exposed to Cassia uniflora seed powder.

Table 4 .
Germination of Parthenium hysterophorous seeds exposed to Cassia uniflora seed powder water extract.