To elucidate the mechanism of callose plug formation, we studied the time span taken for pollen tubes of Camellia japonica, from the start of plug formation until the stage of plug ingrowth, using electron microscopy. A cell membrane was detected around the plugs at all stages of plug formation, and a small amount of cytoplasm was present near the plugs except for those in the earliest stage of formation. Plug ingrowth proceeded even in the vacuole region of the tube, without any supply of cytoplasm. The cytoplasm near the plugs contained a number of granules, organelles and other structures, but none of these reacted with the anti-callose antibody, whereas, the plugs were intensely labeled at all stages of formation. The results suggest that the plugs are not formed by a successive supply of callosic granules to the inner layer of the tube wall, but by inward auto-growth of a portion of the callosic inner layer of the tube wall, dependent on preferential callose synthesis.

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Pollen morphology of Notopora schomburgkii Hook. f. was examined using light (LM), scanning (SEM) and transmission electron microscopy (TEM). Pollenkitt ropes were observed, and are reported for the first time on pollen grains of N. schomburgkii, Ericaceae. With TEM these ropes show lipidic ("pollenkitt-like") electron density but also show some resistance to acetolysis.

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Pre-medical treatment before pollen dispersal is important for Gramineae pollinosis. To estimate the starting date of pollen dispersal, we investigated the relationship between grass-pollen dispersal and early spring meteorological data. For 22years, from 1984 to 2005, the quantities of dispersed pollen in Morioka City, were observed daily using a Durham Sampler. As an index, the earliest starting day for pollen dispersal (EDPD) was defined as the date when 0.3/cm^2/day was observed for two consecutive days. Meteorological data were collected from the database provided by the Morioka Local Meteorological Observatory. The correlations with the EDPD were calculated based on the accumulated daily mean-, maximum- and minimum-temperatures, accumulated sunshine duration, and accumulated amount of global solar radiation from April 1^<st> to 15^<th>. As a result, the highest correlation coefficient (r=-0.831, p<0.001) was obtained between the EDPD and the accumulated daily maximum temperature. The mean and range of the EDPD from 1984 to 2005 in Morioka City were April 30.3 and the period from April 15^<th> to May 16^<th>, respectively. Using a regression equation y=-0.2529x+168.53, where 'x' is the accumulated daily maximum temperature from April 1^<st> to 15^<th>, we could estimate the earliest starting day of pollen dispersal with an accuracy of ±4.1days.

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Pollen yield per male inflorescence in a young Alnus sieboldiana community was measured in 1987 and 1988. The seven to eight year old community was growing on freshly dumped detritus with little humus. Male inflorescences from four trees in the study community were sampled at suitable dates before pollen release on 27 March 1987 and 8 April 1988. Number of bracts per inflorescence, number of stamens per bract, and number and dry weight of pollen per stamen were measured, and pollen yields per inflorescence were estimated by multiplying the quantities of pollen grains per stamen by the number of stamens per inflorescence. The number of pollen grains per stamen, taken from trees bearing a large number of stamens per inflorescence, was small whereas for trees with a small number of stamens, the pollen number per stamen was large. No relationship between pollen weight per stamen and the number of stamens per inflorescence was recognized. For trees showing the minimum dry weight for a single pollen grain, the number of pollen grains per stamen was maximal in both years. Comparison of pollen yields per inflorescence between the study years showed that the number in 1987 was less than that in 1988, while the weight was approximately equal in both years; in 1988 a large number of small, light grains were produced. Mean numbers of pollen grains per stamen for the four sample trees in 1987 and 1988 were 10,720 and 14,410, respectively, whereas pollen weights were 0.142mg and 0.126mg, giving a mean single pollen grain dry weight of 13.5×10^<-6>mg and 8.99×10^<-6>mg, respectively. Mean pollen quantities per inflorescence in 1987 and 1988 were 9.94×10^6 grains and 16.5×10^6 grains, and weighed 133mg and 145mg, respectively.

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We measured the annual production rates of Clerodendrum trichotomum pollen grains in a young C. trichotomum plantation in the nursery of the Kyoto Prefectural University Campus, Kyoto. Pollen production rates were determined on a land-area basis from the number of 4-staminate flowers/corollas that opened in the study community and the mean number and dry weight of pollen grains contained in the flowers before pollen release. The mean number of pollen grains per stamen was 3,459. The mean dry weight of pollen per stamen determined from the difference between the mean weight of anthers before and after pollen release was 0.4311mg, giving a mean single pollen grain dry weight of 125×10^<-6>mg. The mean numbers and dry weight of pollen grains per flower were 13,840 and 1.724mg, respectively, for the four stamens borne by each flower. The ratio of pollen grain number to a single ovule was calculated to be 3,459 grains, as there were 4 ovules per flower. In 2003 the yield of opened flowers per 1m^2 land area of the study community, measured using litter traps plus the clipping method at the end of the study, was 1,585.0/m^2. Therefore, the rates of pollen grain production by this C. trichotomum community in terms of grain number and dry weight were estimated to be 21.9×10^6/m^2 and 2.73g/m^2, respectively.

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We measured the annual pollen production rates of Salix pseudoyoshinoi in 2003 in a young (tree age, 8 to 11years) and pure stand of S. pseudoyoshinoi. No female trees were identified within a 20×40m plot set, and no female inflorescences or infructescences were caught with litter traps. Pollen production rates were determined on an area basis from the number of male inflorescences in the studied stand, and the mean number and dry weight of pollen grains contained in male inflorescences before pollen release. The mean number of pollen grains per stamen was 3,883. The mean dry weight of pollen per stamen was 0.02228mg, giving a mean single pollen grain dry weight of 5.8×10^<-6>mg. The mean number and dry weight of pollen grains for the two stamens borne by each flower were 7,766 grains and 0.04456mg respectively, and, per inflorescence, were 0.967×10^6 grains and 5.54mg. These figures were obtained by multiplying the quantity of pollen grains per flower by the mean number of flowers per inflorescence. The yield of open male inflorescences per hectare of the study stand, measured with litter traps, was 8.2067×10^6/ha/yr. Therefore, the production rates of pollen grains from this S. pseudoyosinoi stand, in terms of grain number and weight, were estimated to be 7.93×10^<12>/ha/yr and 45.4kg/ha/yr, respectively.

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