Germination of Sweet Sorghum Seeds in Different Water Potentials

Abstract

The implantation of sweet sorghum has been shown as viable alternative in crop rotation in sugar cane plantation reform areas. The seed environment in the field is complex and several factors, such as different genotypes and osmotic stress, can negatively influence the seeds water uptake and, therefore, the sequence of germination events can be compromised. In this context, the objective of this study was to evaluate the different physiological responses of sweet sorghum seeds ( Sorghum bicolor (L.) Moench) belonging to the hybrids CV 007 and CV 147 and cultivar BRS 506 when submitted to substrates with different water potentials (-0.1, -0.2, -0.3, -0.4, and -0.5 MPa) using solutions of polyethylene glycol (PEG 6000). The seeds remained in Biochemical Oxygen Demand-type germination chambers, under constant white light and the temperature of 25°C for 14 h in the high temperature and 10 h in the low temperature. The moisture of the substrates was regularly monitored. The physiological potential of the genotypes was evaluated using the following characteristics: first count, germination, germination speed index (GSI), root length, and fresh and dry weights of seedlings. In general, germination and early growth of seedlings were negatively affected by the reduction of water potentials below -0.1 MPa, which was also damaging to the GSI of the seeds. Germination and growth of seedlings of the hybrids CV 007 and CV 147 and of the cultivar BRS 506 were affected by reduced water potentials starting at -0.1 MPa. The seeds of hybrid CV 147 were more tolerant to simulated water stress with PEG 6000 than those of hybrid CV 007 and cultivar BRS 506.