Involvement of Endomannanase in the Control of Tomato Seed Germination under Low Temperature Conditions

The cause of differences in germination rates in a cold-toleranttomato line (PI341988), a control line (UC82B), and six progenylines stemming from crosses and backcrosses between the twoparent lines was investigated. Pursuant to earlier work showingthat differences in germination ability at 12°C are dueto the barrier imposed by the endosperm layer, we analysed theactivity of cell-wall-hydrolysing enzymes extracted from theselines. A significant increase in endomannanase activity wasfound in plant line PI341988 prior to germination at 12°C.Extracts of PI341988 seeds that had imbibed at either 12 or25°C exhibited higher endomannanase activity than theircounterparts from plant line UC82B. Moreover, a positive relationshipwas found between germination ability at low temperature andendomannanase activity in the six progeny lines. Analysis ofendomannanase activity in sub-regions of the seed indicatedthat the increase in activity prior to germination was higherin the micropylar endosperm cap than in the rest of the seed.Exogenous application of mannanase originating from soil-bornebacteria increased germination rates under both moderate andlow temperature conditions. Cellulase (endo-1,4-ß-glucanase)activity was also found to be higher in plant line PI341988.However, the activity of this enzyme probably increases aftergermination and it is therefore not considered as a key enzymecontrolling germination at low temperatures.Copyright 1995,1999 Academic Press Lycopersicon esculentum, tomato, seed germination, cell wall