Graham M. Simpson

Leaf analysis for abscisic, phaseic and 3-indolylacetic acids by high-performance liquid chromatography

Abstract High-performance liquid chromatography (HLPC) is described for the purification and analysis of abscisic acid (AbA), phaseic acid (PA) and 3-indolylacetic acid (IAA) extracted from Sorghum bicolor leaves . The method is rapid, suitable for automation and capable of accommodating large numbers of samples. Detection limits are less than 1 ng for each hormone. Recovery efficiency is 75% for AbA and PA and 64% for IAA. After initial extraction and partition, AbA, PA and IAA were purified together as ammonium salts (ion pairs) on polyvinylpyrrolidone. This was followed by further purification and separation of the three hormones on preparative C 18 reversed-phase HPLC (5-μm spherical particles). Analysis of AbA and PA was by absorption phase silica HPLC (5-μm spherical particles) with detection by UV absorption. Analysis of IAA was by C 18 reversed-phase HPLC (5-μm spherical particles), with fluorescence detection.

Dormancy and enzyme levels in seeds of wild oats

Abstract Nine enzymes were compared in dry and steeped mature dormant and non-dormant seeds of wild oats. In dry seeds only glutamate-pyruvate transaminase and phosphoglycerate kinase were greater in non-dormant seeds. In steeped non-dormant seeds glucose-6-phosphate dehydrogenase activity doubled while the enzyme declined sharply in dormant seeds. Increases in isocitrate dehydrogenase, glutamate-oxaloacetate transaminase and acid phosphatase in non-dormant seeds, during steeping, are consistent with the hypothesis that the pentose phosphate and glycolysis-tricarboxylic acid pathways are involved in the control of dormancy of wild oat seed.

Diurnal changes of leaf water potential, abscisic acid, phaseic acid and indole-3-acetic acid in field grown Sorghum bicolor L. Moench

Summary Diurnal changes of leaf water potential, abscisic acid, phaseic acid and indole-3-acetic acid were studied in field grown sorghum. Leaf water potential fluctuated over a range of -0.84 to -1.82 MPa with two distinct low value peaks at 10.00 and 16.00 h. Abscisic acid exhibited a distinct diurnal variation and fluctuated over a range of 45–110 ng g-1 fresh wt. with two distinct peaks at 08.00 and 18.00 h. Abscisic acid levels, except those from 10.00 to 17.00 h were, negatively correlated with leaf water potential and began to increase at leaf water potential values around -1.0 MPa. Phaseic acid levels were low compared to abscisic acid levels, but fluctuated in a manner similar to abscisic acid with peaks at 10.00 and 18.00 h. Fluctuations in indole-3-acetic acid levels were very small.

The Problem of Plant Breeders

The art of plant breeding, particularly successful in the last one hundred years, but nevertheless several thousand years old, relies essentially on the identification of superior traits in individuals. These individuals are either removed from the general population and multiplied to constitute a new population with superior attributes or crossed to other plants to combine specific characteristics which are desirable from an agronomic or utilization perspective.