Dry Matter Yields and Photosynthetic Rates of Diploid and Hexaploid Triticum Species

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Abstract
The above ground dry matter yields of two wild diploid Triticum species averaged 76 per cent of that of two hexaploid bread wheat varieties in field trials carried out over five years. A cultivated diploid species, T. monococcum, gave similar dry matter yields to the bread wheat varieties but had a longer growth cycle. The flag leaves of wild diploid species had higher rates of photosynthesis than those of the bread wheat varieties both when expressed per unit area of leaf or per unit weight of chlorophyll. Photosynthetic rates of other organs, expressed per unit weight of chlorophyll were also greater for the wild diploids than for hexaploids. For snoots at the stage when their flag leaves were fully expanded, the investment in photosynthetic machinery, as measured by chlorophyll concentration, was less in the two wild diploids than in the hexaploids. This compensated for the high photosynthetic rate of the former, such that the specific growth rates, assessed by carbon-14 fixation per unit shoot dry matter, were similar.