. The Caribbean forester. Forests and forestry Caribbean Area Periodicals; Forests and forestry Tropics Periodicals. 54 Caribbean Forester. Figure 2. Comparative heights of Caribbean pine after 30 weeks exposure to 5 different photoperiods. Note that 8-hour day seedling is shorter than the 12-, 14-, and 16-hour seedlings which are shorter than the seedling with 11 hours interrupted light. Growth and development of Honduras pine (Plnus caribaea v. hondurensis) exposed to various photoperiods were observed in a study at Beltsville, Maryland, with seed ob- tained from British Honduras. Approximat
. The Caribbean forester. Forests and forestry Caribbean Area Periodicals; Forests and forestry Tropics Periodicals. 54 Caribbean Forester. Figure 2. Comparative heights of Caribbean pine after 30 weeks exposure to 5 different photoperiods. Note that 8-hour day seedling is shorter than the 12-, 14-, and 16-hour seedlings which are shorter than the seedling with 11 hours interrupted light. Growth and development of Honduras pine (Plnus caribaea v. hondurensis) exposed to various photoperiods were observed in a study at Beltsville, Maryland, with seed ob- tained from British Honduras. Approximate ly 2 months after germination, the seedlings were divided into 5 groups, with the average height of the seedlings approximately the same in each group, Figure 1. Each group was exposed to one of five photoperiods: 8, 12, 14, 16, and 11 hours per day. The 11- hour seedlings received light in two separate periods, as explained below. Each group of pines was placed on a greenhouse truck for transporting into and out of its appropriate photoperiod The 8-hour seedlings were moved into the greenhouse at 8 and into a dark chamber at 4 p. m. Also at 4 , the 12-hour trucks were wheeled into a chamber illuminated by incandescent bulbs (Downs, Borihwick, and Piringer; 1958) and left to 8 ; the 14- hour seedlings were left under incandescent lights until 10 , the 16-hour seedlings to midnight, and the interrupted-light seedlings were in the illuminated chamber from 11 to 2 The light intensity within the chambers was 40 footcandles and the mini- mum temperature was 70°F. The general effect on Honduras pine of extended photoperiod was to increase both 1/ Photoperiod facilities were provided by R. J. Downs, Plant Physiology Pioneering Research Laboratory, Agriculture Research Service, Beltsville, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration an
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