Effects of temperature and water potential on the germination of muskmelon cultivars

Abstract

SUMMARYThe rate and final germination of four muskmelon cultivars (Cucumis melo) were examined in response to incubation temperatures of 20, 26 and 32°C. Germination was also characterised at 26°C pr 32°C over a range of water potentials from 0 to ‐ 1000 kPa achieved with solutions of polyethylene glycol. The germination of one cultivar, TAM‐Uvalde, was consistently slower at 20°C than at 26°C or 32°C. The other three cultivars, Perlita, TAM‐Dew and Greenflesh, were inhibited by incubation at 32°C. However, the germination responses of cvs Perlita, TAM‐Dew and Greenflesh at 26°C or 32°C improved as water potentials were reduced from 0 to – 200 or – 400 kPa. Cv. TAM‐Uvalde was extremely sensitive to water stress and failed to germinate at water potentials below – 600 kPa when incubated at 26°C. The inhibition of germination at low water potentials was partially reversed in all cultivars by increasing the incubation temperature from 26°C to 32°C. It is suggested that the inhibition of germination at 0 kPa (distilled water) was due to a seed coat‐mediated barrier to oxygen that could be reversed by removal of the seed coat or exposure to an oxygen‐enriched atmosphere.