caa a22 4500 47580676X CHVBK 20180406123749.0 cr unu---uuuuu 170329e20000301xx s 000 0 eng 10.1007/BF00984100 doi (NATIONALLICENCE)springer-10.1007/BF00984100 Cruden R. Department of Biological Sciences, University of Iowa, 52242, Iowa City, IA, USA aut Pollen grains: Why so many? [Elektronische Daten] [R. Cruden] My objective is the examination of selective forces that affect pollen number. Relationships among other floral traits of animalpollinated plants, including pollen size, stigma area and depth, and the pollen-bearing area of the pollinator may affect pollen number and also provide a model to examine how change in one trait may elicit change in other traits. The model provides a conceptual framework for appreciating intra- and inter-specific differences in these traits. An equivalent model is presented for wind-pollinated plants. For these plants the distance between putative mates may be the most important factor affecting pollen number. I briefly consider how many pollen grains must reach a stigma to assure fruit set. I use pollen-ovule ratios (P/Os) to examine how breeding system, sexual system, pollen vector, and dispersal unit influence pollen grain number. I also compare the P/Os of plants with primary and secondary pollen presentation and those that provide only pollen as a reward with those that provide nectar as part or all of the reward. There is a substantial decrease in P/O from xenogamy to facultative xenogamy to autogamy. Relative to homoecious species the P/Os of species with most other sexual systems are higher. This suggests that there is a cost associated with changes in sexual system. The P/Os of wind-pollinated plants are substantially higher than those of animal-pollinated plants, and the available data suggest there is little difference in the pollination efficiency of the various animal vectors. The P/Os of plants whose pollen is dispersed in tetrads, polyads, or pollinia are substantially lower than those of species whose pollen is dispersed as monads. There was no difference in the P/Os of plants with primary and secondary pollen presentation. The P/Os of plants that provide only pollen as a reward were higher than those that provide nectar as a reward. All of these conclusions merit additional testing as they are based on samples that are relatively small and/or systematically biased. Springer-Verlag, 2000 Animal-pollination nationallicence breeding systems nationallicence duration stigma receptivity nationallicence pollen grain number nationallicence pollen grain size nationallicence pollen packaging units nationallicence pollenovule ratios nationallicence secondary pollen presentation nationallicence sexual systems nationallicence stigma area and depth nationallicence wind-pollination nationallicence Plant Systematics and Evolution Springer-Verlag 222/1-4(2000-03-01), 143-165 0378-2697 222:1-4<143 2000 222 606 https://doi.org/10.1007/BF00984100 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00984100 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Cruden R. Department of Biological Sciences, University of Iowa, 52242, Iowa City, IA, USA aut NATIONALLICENCE 773 0- Plant Systematics and Evolution Springer-Verlag 222/1-4(2000-03-01), 143-165 0378-2697 222:1-4<143 2000 222 606 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer