MSc

“Seed invigoration and dormancy studies in snake gourd (Trichosanthes anguina L.)” were carried out at Department of Olericulture, College of Horticulture, Kerala Agricultural University, Vellanikkara, Thrissur during 2004-2005. This study aimed at standardizing seed invigoration techniques in snake gourd that can break dormancy and improve seed vigour and studying the impact of invigoration techniques on storability as well as field performance.

Among the different invigoration treatments tried, mechanical scarification by way of seed rupturing was the most effective one followed by acid treatments (5N H2SO4, 5N HCl and 5N HNO3 for 10-20 minutes), hot water soaking (400 C for 5 minutes) and treatment with 1 % KNO3 for 12 hours. These treatments could break the dormancy of snake gourd seeds from the freshly extracted state onwards and improve the seed vigour. From the fourth month onwards, untreated seeds also showed higher germination. Treatments such as water soaking, GA3 250 / 500 ppm, NAA 100 ppm, 0.5 % NaH2PO4 and 0.5 % KH2PO4 did not show any positive influence on dormancy release.

It is evident from the present study that dormancy in seeds of snake gourd is due to water impermeable seed coat and this is naturally broken only four months after extraction and if the seeds are to be used immediately after extraction or till three months afterwards, an invigoration treatment is inevitable.

An insight in to the changes in the anatomy of seed coat thickness revealed the differences in the layer wise coat thickness of invigorated seeds, stored seeds and fresh seeds. The stored seeds had lesser coat thickness as in the case of invigorated seeds. In contrast, untreated fresh seeds had higher coat thickness and this acts as a mechanical barrier for water imbibition.

The study on moisture imbibition rate revealed that the seeds subjected to mechanical scarification imbibed water more rapidly after 24 hours and resulted in higher and early germination and high speed of release of dormancy. The stored seeds as well as seeds invigorated with acids and hot water also displayed high imbibition rate due to reduced seed coat thickness and opening of specialized cracks in seed coat. On the other hand, untreated seeds showed lesser water imbibition.

There was a gradual reduction in quality parameters like germination percentage, speed of germination and vigour indices during storage of invigorated seeds. This indicates that the invigorated seeds can be supplied to farmers only for immediate use and they are not amenable to storage beyond one to two months.

Electrical conductivity of seed leachates was significantly influenced by the invigoration treatments during the period of storage. The EC values showed increasing trend with increase in duration of storage. This confirms the usefulness of electrical conductivity study as a rapid and effective indicator of seed deterioration during storage.

The seeds subjected to mechanical scarification and seeds from previous Kharif crop were found to have maximum field emergence and the seeds treated with 1 % KNO3 recorded highest fruit set, earliness, higher yield, maximum fruit weight as well as higher seed yield followed by stored seeds from previous Kharif crop. All other treatments were also superior in field performance when compared to untreated fresh seeds. Thus it can be seen that the initial advantage gained through seed invigoration has been sustained to a larger extent in the field performance as well.