. Day length and crop yields. Plants; Crop yields; Plant photoperiodism. r«r Pyrethrum produces flowers, which are the source of insect powder, only when grown in localities where the photoperiods are long. Under short photoperiods the plants remain as rosettes. vail in any given region arc as important as moisture and soil fertility in determining the specific behavior and economic value of varieties which it may be desired to grow. Although the length of photoperiod in any particular locality changes from day to day throughout the season, the photoperiods of corresponding days in successive
. Day length and crop yields. Plants; Crop yields; Plant photoperiodism. r«r Pyrethrum produces flowers, which are the source of insect powder, only when grown in localities where the photoperiods are long. Under short photoperiods the plants remain as rosettes. vail in any given region arc as important as moisture and soil fertility in determining the specific behavior and economic value of varieties which it may be desired to grow. Although the length of photoperiod in any particular locality changes from day to day throughout the season, the photoperiods of corresponding days in successive years are always of the same length. Therefore, the seasonal variations in this environmental factor can be predicted far more accurately than the variations in temperature, moisture, or soil fertility. It is not a difficult task to determine under controlled experimental conditions many of I he special photoperiodic and temperature require- ments of individual varieties. By making such determinations one can readily tell in advance whether certain varieties of soybean-, pea-. onions, barley, and many other plant- arc adapted to the photo- periodic conditions known to prc\ ail in a given locality. Such detailed experiments can be substituted, at least in part. for the far more costly necessity of growing or at tempt ing to grow crops in any given locality to obtain the same information. If a variety were found by experi- ment to be unadapted, it would not be grown in the held. Either an existent variety that was adapted to the locality would be chosen,or il none was known, one or more which would be suitable could be bred. 18273 i-'. 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 Parker, M. W. (Marion Wesley), 1907-; Borthwick, H. A. (Harry Alfred), 1898-. Washington, D. C. : U. S. Dept. of Agriculture
Size: 2762px × 905px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisherwashingtondcusd, booksubjectplants
