Abstract
Seeds of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench.] were submitted to different osmotic potential levels induced by polyethylene glycol (PEG) with the objective of evaluating the effects of drought stress on seed germination and early seedling growth. Seeds were arranged in paper rolls and soaked in PEG solutions prepared with osmotic potentials 0.0 (control), -0.2, -0.4, and -0.8 MPa and kept into a seed germinator, at 25 °C for 18 days. A completely randomized design in a 2 × 4 factorial scheme with four replications of 50 seeds each was used. The results showed that by increasing of the osmotic potential level, germinated seed number, germination rate index, root and shoot length, shoot and root dry matter, and seedling vigor index (SVI) decreased, while mean germination time (MGT) and root: shoot ratio (RSR) increased in both crops. Additionally, the maize was more susceptible than sorghum to drought stress, with germination response declining more rapidly with decreasing osmotic potential. Sorghum crop tolerates water stress of up to -0.2 MPa, without reducing germination of the seeds; however, the growth of shoots and roots are inhibited. Drought stress limits the process of seed germination and early growth of maize seedlings.
Highlights
Maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench.] are two of the most important cereal crops in the world due to their use for food, animal feed/forage, for ethanol production and other industrial products
This research was carried out to investigate the effects of drought stresses induced by polyethylene glycol (PEG) on seed germination and early seedling growth of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench.]
The normality of data was previously tested by the Kolmogorov-Smirnov test and data were submitted to analysis of variance (ANOVA), and means of plant species and osmotic potentials were compared by the F and Tukey test, respectively, both at the 0.05 level of confidence
Summary
Maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench.] are two of the most important cereal crops in the world due to their use for food, animal feed/forage, for ethanol production and other industrial products. Many studies on plant responses to drought stress induced by PEG solutions with regard to seed germination and seedling growth have been recently reported, including studies of crops, common bean (Machado-Neto et al, 2006), soybean (Teixeira et al, 2008), sunflower (Ahmad et al, 2009), sorghum (Oliveira & Gomes-Filho, 2009), maize (Khodarahmpour, 2011), and cotton (Meneses et al, 2011). Identification and understanding the mechanisms of drought tolerance in sorghum have been major goals of plant physiologists and breeders which includes prolific root system, ability to maintain stomatal opening at low levels of leaf water potential and high osmotic adjustment (Rajendran et al, 2011; Tsago et al, 2014) Information about this moderate tolerance to drought during the seed germination and seedling establishment stages are still incipient and inconclusive. This research was carried out to investigate the effects of drought stresses induced by polyethylene glycol (PEG) on seed germination and early seedling growth of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench.]
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