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Articles by R.E.L. Naylor
Total Records ( 4 ) for R.E.L. Naylor
  M.Z. Alam , T. Stuchbury , R.E.L. Naylor and M.A. Rashid
  Water uptake and pattern of germination of two rice cultivars differing in seed size were determined in iso-osmotic solutions of NaCl and polyethelene glycol, different concentrations of CaCl2 and combinations of NaCl and CaCl2. The results demonstrated that full imbibition of rice seeds occurred at around 30% moisture content (mc) and the critical mc for germination was around 25-30%. Although rates of water uptake in rice seeds were reduced with increasing salinity, rice seeds attained full imbibition by 48 h up to 150 mM salinity and reached at least critical mc by 72 h up to 250 mM salinity. Water uptakes in NaCl solutions were greater than in iso-osmotic solutions of PEG and rice seeds did not attain even critical mc in PEG solutions lower than -0.232 MPa even after 72 h. When Ca was added in combination with NaCl, water uptake in rice seeds increased. Water uptake in smaller seed was less during the first 12 h of imbibition than larger seeds. However, equilibrium mc was attained within 48 h in both large and small seed. The onset of germination declined with increasing concentrations of NaCl and in iso-osmotic solutions of PEG, particularly below-0.457 MPa osmotic potential. Large and small grain rice seed differed significantly in their response to salt and osmotic stress. Supplemental Ca (3 to 9 mM) significantly increased germination percentage compared to no Ca salt stress. Three mM Ca completely offset the deleterious effects of 150 mM NaCl and 6 mM Ca partially offset the deleterious effects of 225 mM NaCl on rice seed germination. Nine mM Ca significantly increased germination in large seed cultivar but not in the small grain cultivar compared to 6 mM Ca.
  M.Z. Alam , T. Stuchbury and R.E.L. Naylor
  The effect of reduced osmotic potentials on germination and early seedling growth of four rice cultivars differing in salt tolerance were studied using iso-osmotic solutions (0, -0.232, -0.457, -0.677, -0.906 and -1.129 MPa) of NaCl and polyethylene glycol (PEG 4000). Seed germination and early seedling growth were assessed using four replicates of 25 seeds at 21±10C in the dark using paper towel method. Onset of germination, germination rate and seedling growth, all declined with increasing concentrations of both NaCl and PEG, the former being more inhibitory. Germination and growth processes were mainly affected at and above -0.457 MPa osmotic potential in both NaCl and PEG. Rice cultivars differed greatly in their tolerance to salt and water stress. However, the differences were well pronounced in NaCl but less so in PEG. The imposition of water stress by PEG for 9 days did not permanently inhibit germination or induce dormancy. However, salt stress appeared to be lethal than the equivalent osmotic potentials of PEG. Salt tolerant cultivars (V2 and BR23) performed consistently better under salt stress and consistently poor under osmotic stress compared with salt sensitive cultivars (V1 and IR8). These results suggested that the salt tolerance of rice cultivars is probably determined by their ability to withstand excessive Na+ and Cl‾ ions rather than their ability of water stress tolerance.
  M.G. Ali , R.E.L. Naylor and S. Matthews
  The effect of seed ageing of 14 Bangladeshi rice cultivars was investigated to aid the identification of rice genotypes tolerant of low temperature during germination. This would facilitate breeding cultivars suitable for direct wet-seeding in the cooler Boro season in Bangladesh. The present study was carried out at the University of Aberdeen, UK during 1999. The results of the experiment on temperature gradient plate at a range of constant temperatures (13.7-37.3oC) revealed a number of cultivars (BR1, KS and KG) were to be of lower physiological quality than the rest. It was therefore, necessary to confirm whether the reason for their relatively poor performance was physiological deterioration. Seed survival curves of all cultivars at 24% moisture content (mc) and 45oC for up to 96 h tested at 21oC showed a clear separation in germination after 48 h ageing. Cultivars BR1, KS and KG were identified as the lowest quality seed lots with 0, 35 and 17% germination, respectively. Cultivar samples had different Ki (initial seed quality) after probit transformation with a range 79.30% (e.g. cv. KG) to 99.36% (e.g. cv. BR29), but surprisingly, had different slopes. The steepest slope was found for cv. BR11 (-0.046) and shallowest of that was for cv. BR24 (-0.017). The rates of germination of the faster germinating cultivars (8 cultivars, around 0.30 seed d-1) declined more rapidly and at 72 h ageing the rates of germination of all cultivars were closer. Cultivars KS and KG had the least rates of germination (around 0.15 seed d-1). Only when the lower quality cultivars (BR1, KS and KG) were included, were significant relationships found between measures of physiological age (48 h ageing germination, Ki and viability period) and final germination at lower temperature. The results of the study suggested that seed quality as well as genotype might be responsible for reducing final germination of cultivars. The present study also revealed that germination of seed lots of 14 rice cultivars in low temperature was influenced more by genotype than seed quality.
  M.G. Ali , R.E.L. Naylor and S. Matthews
  Germination of 15 rice cultivars were investigated on a temperature gradient plate with a range of temperatures 13.7-37.3 °C to identify rice genotypes tolerant of low temperature which would facilitate in cultivar selection for winter sown rice (Boro rice) in Bangladesh. The results demonstrated a plateau of more than 90% final germination between 18 and 33 °C for eleven cultivars. Three cultivars had a plateau of less than 90% germination. At the lowest temperature seven cultivars achieved 80% germination whereas lower quality cultivars showed less than 8% germination. The rest of cultivars were intermediate with about 30-50% germination. The rate of germination (the reciprocal of median germination time) for all cultivars increased linearly from 13.7 up to 30.9 °C and then declined rapidly between 30.9 and 37.3 °C. At optimum temperature cultivars with lower quality seed sample (BR1, KS, KG and BR30) had the lowest rates of germination along with cv. BR5. Rates of germination at higher temperatures (20.1 and 30.9 °C) were significantly related to the rates of germination at lower temperature (13.7 and 15.8 °C). The base temperature differed little between cultivars (range 12.6–13.9 °C) and optimum temperature ranged from 29.9 to 33.5 °C (mean 32.1 °C). Thermal time to achieve 50% germination at sub-optimal temperatures ranged from 526 to 1667 °C h and differed significantly between cultivars. Cultivars with lower quality seeds and BR5 required than above 900 °C h. The application of these findings to the development of routine methods to identify rice genotypes able to germinate at lower temperature is emphasized. Measurements of rates of germination at higher temperatures (20 and 30 °C) could provide a relatively rapid screening method indicative of low temperature performance for large numbers of genotypes.
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