Archive image from page 5 of Day length and crop yields. Day length and crop yields daylengthcropyie507park Year: 1942 Strawberries produce abundant fruit when the day length is 14 or 15 hours, but they usually do not flower when the day length is only 1 0 or 11 hours. of plant growth. The shading of certain crops, such as to- bacco and coffee, has become an established field practice, whereas the elimination of shade through removal of trees or other obstructions has been found advanta- geous for various other crops. Despite these gen- eral observations, certain details of plant behavior
Archive image from page 5 of Day length and crop yields. Day length and crop yields daylengthcropyie507park Year: 1942 Strawberries produce abundant fruit when the day length is 14 or 15 hours, but they usually do not flower when the day length is only 1 0 or 11 hours. of plant growth. The shading of certain crops, such as to- bacco and coffee, has become an established field practice, whereas the elimination of shade through removal of trees or other obstructions has been found advanta- geous for various other crops. Despite these gen- eral observations, certain details of plant behavior remained unexplained on the basis of variations in light intensity only, Among these was the fact that in nature many plants bloomed only at definite seasons of the year. Some plants, such as poinsettia, could be propagated by means of cuttings made at various times of the year, but all the new plants, large and small, generally bloomed at approximately the same time. Various economic plants when grown in the North bloomed and set seed but did not do so in the South. Similarly, many kinds grown from seeds were leafy and grew luxuriantly when sown at certain seasons of the year but remained small and went to seed quickly at other seasons. From time to time many explanations for these various behaviors were advanced, but none ad- equately accounted for them.
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Keywords: 1940, 1942, archive, book, bookauthor, bookdecade, bookpublisher, booksponsor, booksubject, bookyear, borthwick_h_a_harry_alfred_1898_, crop_yields, drawing, historical, history, illustration, image, page, parker_m_w_marion_wesley_1907_, picture, plant_photoperiodism, plants, print, reference, u_s_department_of_agriculture_national_agricultural_, vintage, washington_d_c_u_s_dept_of_agriculture, zimmermann_a_albrecht_b_1860
