. Auxins and plant growth. Auxin; Plant growth promoting substances. Herbicides 291 type of injurious effects suffered by grains changes with different times of application. For example, in figure 119 it can be seen that spraying a stand of wheat in early April resulted principally in abnormal position of spikelets in the head. Sprays in mid-April resuked in the occurrence of supernumerary spikelets, and sprays in late April or early May induced abnormal glume formation. In the case of corn several different injurious effects have been described, inchiding the production of brittle stems, seed
. Auxins and plant growth. Auxin; Plant growth promoting substances. Herbicides 291 type of injurious effects suffered by grains changes with different times of application. For example, in figure 119 it can be seen that spraying a stand of wheat in early April resulted principally in abnormal position of spikelets in the head. Sprays in mid-April resuked in the occurrence of supernumerary spikelets, and sprays in late April or early May induced abnormal glume formation. In the case of corn several different injurious effects have been described, inchiding the production of brittle stems, seed of low viability, poor set of the kernels or distorted ears (Rodgers, 1952; Staniforth, 1952). These abnormalities, too, are a function of the time of spray application. Reductions in yield can be closely correlated with some of these injurious effects. Sample data on reduction of yields in peas as a function of time of auxin application are shown in figure 120. It is evident that the germinating seed is most sensitive to the auxin application, for treat- ment at that stage reduced yields to almost zero. A second period of sensitivity occurs as flowering begins. The inverse relationship of this curve with figure 114 may be noted. Yield data for other crops do not always follow the same trend (Derscheid, 1952; Andersen and. 2" 6" Stage Stage 12" Bud Early Stage Bloom Full Blo( TIME OF APPLICATION Fig. 120. The effects of an heibicidal spray of of MCPA (2-methyl 4-chlorophenoxyacetic acid) applied to peas at various stages of development upon subsequent yield (Buchholtz, 1952).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Leopold, A. Carl (Aldo Carl), 1919-. Berkeley, University of California Press
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