ABSTRACT
Although the most reliable tests of cotton (Gossypium hirsutum) seed vigor are based on growth, there continues to be interest in identifying a metabolic marker that correlates with vigor before substantial seed growth has occurred. Our objective was to determine if cotton seed vigor is most correlated with biochemical processes linked metabolically to seed growth. To test this hypothesis, a metabolic process was required that could be 1) assayed nondestructively on individual seeds, 2) linked and unlinked experimentally to seed growth, and 3) correlated with individual seed growth performance during stress. EtOH fermentation appeared to meet these requirements because it could be measured nondestructively and cotton seed growth is inhibited during EtOH biosynthesis, but not EtOH assimilation. For all experiments, high vigor Deltapine 90 (1986 harvest, 11% moisture content) seeds were first imbibed 28 h at 28 C. To measure EtOH assimilation, 50 seeds were incubated individually in air at 28 C for 2 h in test tubes containing 50 uL of 64 mM EtOH. To measure EtOH biosynthesis, 50 seeds were incubated individually in either N2 or CO2 gas at 28 C for 2 h in tubes containing 50 uL of 4 mM ETOH with or without polyethylene glycol (0.8 g mL water-1). EtOH excreted into (biosynthesis) and taken up from (assimilation) the imbibition solution of individual seed was quantified by gas-liquid chromatography. Following either measurement, seeds were cool-tested individually at 18 C for 6 days. Results indicated that cotton seed radicle growth was inhibited, but not stopped during sudden exposures to either N2 gas or PEG. Radicle growth stopped only when both treatments were applied simultaneously. Growth resumed if all stresses were removed within 2 h. Cotton seeds consistently biosynthesized ETOH during anoxic stress and assimilated EtOH in air. The original hypothesis could not be tested, however, because seed performance (radicle growth) during cool testing was not significantly correlated to either EtOH biosynthesis or EtOH assimilation. It was concluded that EtOH metabolism both in the presence and absence of seed growth has limited usefulness as a metabolic marker of cotton seed vigor.
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