. Bonner zoologische Monographien. Zoology. 114 sticky appendages hanging downwards from the micropyle. For only a short period, a few hours, a pollination droplet is exposed during night time and kept between the two appendages. The liquid of the pollination droplet dissolves the sticky secretions and the pollen grains ascend in the pollination droplet to the nucellus of the ovule. The so-called airsacs of the pollen grains work as buoys in the pollination droplet as was already proposed by Doyle & O'Leary (1935). The air sacs apparently reduce the specific weight of pollen grains. The sm
. Bonner zoologische Monographien. Zoology. 114 sticky appendages hanging downwards from the micropyle. For only a short period, a few hours, a pollination droplet is exposed during night time and kept between the two appendages. The liquid of the pollination droplet dissolves the sticky secretions and the pollen grains ascend in the pollination droplet to the nucellus of the ovule. The so-called airsacs of the pollen grains work as buoys in the pollination droplet as was already proposed by Doyle & O'Leary (1935). The air sacs apparently reduce the specific weight of pollen grains. The small specific weight of pollen grains may help to increase transport intervals in the air, or may make possible upward-transport in a hanging pollination droplet and thus reduce the time span up to fertilization. Support for the buoy-hypothesis is the observa- tion that so-called air sacs are almost exclusively found in gymnosperm species with hanging pollination droplets in which the pollen grains have to ascend to their target. Additional evidence for the buoy-hypothesis are measurements of the sinking velocity of pollen grains in the air which, according to data summarized by KuGLER (1970), seemingly is not strikingly reduced in species, in which the pollen grains have Fig. 3: Pollination system of Pimis mugo (Pinaceae, Gymnospermae). Pollen collection by the pollination droplet and pollen grain transport towards the ovule are shown. Modified after Stützel & Röwekamp (1997).. 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 Bonn, Zoologisches Forschungsinstitut und Museum Alexander Koenig
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Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectzoology
