The pollen morphology of 41 species in 12 of the 13 genera constituting tribes Andromedeae s.s., Gaultherieae, Lyonieae and Oxydendreae of Ericaceae, subfamily Vaccinioideae, was investigated with light (LM) and scanning electron microscopy (SEM). The pollen of the species included in these tribes is stenopalynous: 3-colopor (oid) ate grains in oblate permanent tetrads. Pollen characteristics do not show notable correlation with the tribal classification, although it is observed that the pollen tetrads tend to be compact in Andromedeae s.s., Gaultherieae and Oxydendreae, but usually lobed in Lyonieae, especially in Lyonia. The compact tetrads of tribe Andromedeae are characterized by a thin, perforated septum. Apocolpial exine sculpture of individual grains within the pollen tetrad varies from psilate to coarsely rugulate, the rugulae have a 'secondary sculpture' of faint to well-defined fine or coarse striae. Two main R and S types, six subtypes and seven sub-subtypes of exine are recognized based on the primary sculpture and distinctness of secondary sculpture on the rugulae. A continuous series of variation in both qualitative and quantitative characters of the pollen was observed within all four tribes. Sometimes exine sculpture shows little variation in some genera within these tribes; e.g. Leucothoe (S2 and S2**) within the tribe Gaultherieae, and Agarista (R2-3 and R4) and Lyonia (R3, R3* and R3**) within the tribe Lyonieae. Exine sculpture, degree of tetrad compactness, tetrad size and septum thickness proved to be the most useful characters for helping to clarify the infrageneric classification in Gaultheria, Agarista and Lyonia. An exine surface with secondary striate sculpture is apparently characteristic of subfamily Vaccinioideae, based on our general palynological survey of the Ericaceae.

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Pollen tube growth of Camellia japonica is inhibited by exogenous maltose in contrast, for example, to that of Lilium longiflorum pollen which is promoted. On glucose medium, the tube growth of C. japonica is inhibited competitively by maltose, whereas on sucrose medium is not. Maltose may be involved in pollen tube growth without undergoing cleavage to glucose as pollen has no maltase activity. The present study focusses on the mechanism responsible for this unique inhibition of pollen tube growth by maltose. The effect of exogenous maltose on pollen tube growth in ca. 50 species from different families, representing both monocotyledons and dicotyledons, was examined. Results show that tube growth is inhibited only in pollen belonging to the Theaceae. Although it was not ascertained whether or not maltose was taken up into the pollen cytoplasm, the levels of intermediates related to glycolysis and sucrose metabolism were not affected by maltose, even when the pollen was incubated on a variety of sugar media in the presence or absence of maltose. Several glucosides, for example, phlorizin and salicin, inhibited pollen tube growth in C japonica in a similar way to maltose. These results suggest that inhibition of pollen tube growth is due to binding of maltose to the glucose transporter, which consequently inhibits the uptake of exogenous glucose, but not that of sucrose. It is also likely that the conversion of endogenous sugar into tube wall components is suppressed, although respiration is unaffected.

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Pollen morphology of Schoenoplectus gemmifer was examined with scanning electron microscopy and light microscopy. Pollen grains are of the 'one-pore and six-furrow' type. In equatorial outline they have the appearance of an isosceles triangle while, in polar outline they appear circular or tetragonal. The length of the polar axis is 38.7±2.4μm, the diameter of the equatorial axis is 2.83±1.5μm. and the P/E ratio is 1.37±0.06. The ornamentation is scabrate- punctate. The concavity and convexity are pronounced: in the convex area puncta are absent while the furrow membranes are covered with angular granulae that have some puncta and some microspines. The boundary between the furrow membrane and tectum is well-defined.

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The production rates of pollen, flowers and fruits in a 102-year old Camellia japonica stand were studied in 2000-2003. The rates, in terms of number and dry weight on an area basis, were measured using 24 litter traps set within a 20×26m plot. Pollen yields per flower have been reported previously. Pollen production rates, obtained by multiplying the pollen yield per flower by the number of open flowers per ha, were estimated to be 0.790-1.83×10^<12> (mean, 1.49×10^<12>) grains/ha, and 60.0-139 (mean, 113) kg/ha. Annual fluctuation of pollen production rates during four consecutive years, represented as the ratio of the maximum rate relative to the minimum, was 2.3. The investment of photosynthates in reproduction or total dry matter of flowers and fruits, including pollen, in the stand was 1,470-2,241 (mean, 1,998) kg/ha. Pollen allocation among total matter was 4.1%-6.7%, with a mean of 5.7%.

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Pollen yields per strobilus of Abies firma, in terms of grain number and dry weight, were measured in two productive years. Male strobili from three trees, 60 to 70 years old, in the Kyoto Prefectural University Campus were sampled on suitable dates before pollen release in 1993 and 1995. Pollen yields per strobilus were estimated by multiplying the pollen quantities per stamen by the number of stamens per strobilus. The mean number of stamens per strobilus ranged from 97.4 (Tree#3 in 1995) to 117.3 (Tree#1 in 1993). The quantities of pollen per stamen varied among sample trees and years. The mean numbers of pollen grains per stamen were 1,936 in 1993 and 2,251 in 1995, and the mean dry weights were 0.3333mg and 0.2825mg, respectively. The mean numbers of pollen grains per strobilus were estimated to be 211.0×10^3 in 1993 and 240.7×10^3 in 1995, corresponding to mean weights of 36.10mg and 30.30mg, respectively. The dry weight of a single pollen grain, obtained by dividing the weight by the number of pollen grains per stamen, was in the range of 106 (Tree#3 in 1995) to 203 (Tree#3 in 1993)×10^<-6>mg, and the mean weight was 176×10^<-6>mg in 1993 and 130×10^<-6>mg in 1995.

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The production rates of pollen, male catkins, female strobili and seed cones in a 26-year-old Alnus sieboldiana stand, planted on the site of an old landslide in a Sugi and Hinoki plantation, were studied in 1987 and 1988. These rates, in terms of number and dry weight on an area basis, were measured using litter traps. Male catkins from four trees in the study stand were sampled on suitable dates before pollen release. Number of bracts per catkin, number of stamens per bract, and number and dry weight of pollen grains per stamen were measured, and pollen yields per catkin were estimated by multiplying the mean values for the trees. Mean pollen quantities per catkin were 22.34×10^6 grains and 227.3mg in 1987, and 19.47×10^6 grains and 180.9mg in 1988. The dry weight of a single pollen grain, obtained by dividing the weight by the number of pollen grains per stamen, was 10.29×10^<-6>mg in 1987 and 9.41×10^<-6>mg in 1988. Pollen production rates, obtained by multiplying the pollen yield (by number and dry weight) per catkin by the number of open male catkins per ha, were estimated to be 40.5×10^<12> grains/ha and 412kg/ha in 1987, and 35.1×10^<12> grains/ha and 326kg/ha in 1988. The mean numerical ratio of pollen grains to ovules (P/Ov ratio) for the two study years was 120×10^3. The dry-matter production rates of male components were 829.5kg/ha in 1987 and 755.6kg/ha in 1988, and pollen allocations reached 49.7% and 43.2%, respectively. The investment of photosynthates in reproduction or the mean dry-matter production rate for male plus female components was 1,035.9kg/ha, among which pollen allocation reached 35.7%.

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