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Some observations on germination of Pseudotsuga menziesii (Mirb.) Franco pollen in vitro Ho, Ronghui

Abstract

Pollen morphology, pollen germination, and the effects of nutrients during pollen germination of Pseudotsuga menziesii (Mirb.) were studied. Pollen extraction was done at room temperature and the pollen morphology was studied using a staining technique. Several types of substances were introduced to the medium (double-distilled water) to culture the pollen. The substances were boric acid, calcium nitrate, potassium salt of gibberellie acid, indoleacetic acid, indolebutyric acid, naphthaleneacetic acid, thiamin, water extracts of Douglas-fir seeds, sucrose and stock solution. Incubation of pollen grains was carried out in the growth chamber where light intensity was about 3500 foot-candles during the 12-hour light period each day and the temperature was maintained at 20°G at night and 25°C during the day time. The relative humidity was kept at about 40 percent. Pollen grains were checked daily. Mature pollen grains were at the two-celled stage with two degenerated prothallial cells. When dry, the grains were cup-shaped, while turgid grains were spherical or elliptical without any furrows or sacs. The exine was thin being about 2 microns, and quite smooth. The intine was about 8 microns thick and was of uniform hyaline appearance. The pores in the exine were about 2 microns in diameter; those in the intine were enclosed with a membrane. Boron and calcium ions were very important to the pollen germination and elongation. Pollen germination was stimulated by growth-promoting substances, but was inhibited by fungicide and bactericide. Sucrose solution of 10 to 15 percent was recommended for the osmotic milieu and for nutrient purposes. Stock solution (boron 0.1 g., calcium nitrate 0.3 g., and double-distilled water 100 ml.) is the best for pollen germination and elongation. Pollen grains cultured in the medium containing stock solution B, 10 ppm IAA, and sucrose were found in four-celled stages (tube cell, two sperm cells and stalk cell) after five days. The actual germination of the Douglas-fir pollen in vitro was accomplished in this study. These may be of practical value in ensuring a uniformly high rate of seed production in Douglas-fir seed orchards, but field studies (artificial pollination) are needed to obtain further information.

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