The present work was done to elucidate the impact of gibberellic acid (GA₃) on male meiosis of Brassica campestris L. with an aim to study its cytological peculiarities. Microsporogenesis analysis of distilled water treated sets displayed the normal meiotic and post-meiotic courses. However GA₃ sprayed sets possessed several meiotic manifestations followed by disturbed postmeiosis. In present case meiotic irregularities followed by unusual tetrad configurations such as tetrad having randomly arranged microspores, completely vacant (sterile) tetrad, monad (microsporesac bearing one microspore), dyad (two microspores), triad (three microspores) and polyads (more than four microspores) were registered. As a consequence of such an anomalous microsporogenesis, pollen fertility rate of the present crop has been declined considerably in a dose dependent manner whereas its direct and negative influence on the reproductive success of the test crop has been determined. In ours study, marked dropdown in the reproductive success has been recorded; which was estimated on the basis of rate of increased pollen abortion which in turn led to considerable decreased seed set of crop at maturity.

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Petasites frigidus (L.) Fries had the stable chromosome number of 2n=60. However, P. radiatus (J. F. Gmel.) Toman had a mixoploidy since the majority of the mitotic metaphase cells showed 2n=86∼90 (83% metaphase cells studied) and 2n=30 (14% metaphase cells studied). Numerous data on chromosome numbers of Petasites reported in various species of the genus in 1970′s to 1980′s commonly reported 2n=60 by several authors should be rechecked and determined again.

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Perillula reptans was karyomorphologically studied. This species had the resting chromosomes of the complex chromocenter type, the mitotic prophase chromosomes of the proximal type, and had 2n=14 chromosomes in the mitotic metaphase with basic chromosome number of x=7. The chromosome numbers of this species was reported here for the first time. The chromosome complement showed a gradual (monomodal) gradation in length from the longest (2.8 μm) to the shortest (1.7 μm) chromosomes, and consisted of six submedian-centromeric and eight subterminal-centromeric chromosomes.

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Chromsome numbers and karyotypes of four taxa of Launaea (Asteraceae) were studied. They showed various chromosome numbers and karyotypes. Launaea nudicaulis (2n=18) had 18 median chromosomes, L. capitata (2n=18) had 18 median chromosomes, L. fragilis subspecies fragilis (2n=16) had nine median and seven submedian chromosomes and L. fragilis subsp. teniuloba (2n=32) had 31 median and one submedian chromosomes.

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Two new forms of Pogonia different from P. japonica and P. minor were found in Japan: One was called ‘Miyamatokisou’ collected in Mt.Hakusan and the other one was still unnamed and collected in Higashi-Hiroshima City, Hiroshima Prefecture. The karyotype of Pogonia called ‘Miyamatokisou’ was 2n=18 and consisted of 18 median-centromeric chromosomes but was a little bit different from that of P. minor (2n=18). That of Pogonia collected Higashi-Hiroshima-City was 2n=20 that was consisted of 16 median-centromeric chromosomes and four terminal-centromeric chtomosomes, and similar to that of P. japonica (2n=20). Origin and relationships of those two new forms were analyzed by RAPD (the randomly amplified polymorphic DNA) technique: According to the results of RAPD obtained here, Pogonia called ‘Miyamatokisou’ and Pogonia from Higashi-Hiroshima City had different DNA fragment-patterns from P. japonica, P. minor and their F₁ hybrids. Additionally, Pogonia called‘Miyamatokisou’was different from Pogonia originated from Higashi-Hiroshima City although their flower shape was similar to each other. It was confirmed that newly naturally developed Pogonia from P. japonica and P. minor existed in nature according to the RAPD analysis.

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A method for meiotic chromosome preparation including a hypotonic treatment of suspending pollen mother cells (PMCs) released from male strobili was developed in several conifer species. Preparations of meiotic chromosomes were easily made just by dropping of an aliquot of fixative suspending PMCs on a glass slide. The preparations of meiotic chromosomes obtained in all 16 species used of seven confer families were adequate for conventional observation on sequences of meiosis and spread chromosomes at metaphase I. Fluorescent bandings using chromomycin A₃ (CMA) and DAPI were applied the preparations to reveal chromosome configuration of chromosomes with fluorescent band. In male plant of Podocarpus macrophyllus DAPI-bands appeared on a trivalent of XXY-type sex chromosomes indicating structural relationships among them and in Sequoia sempervirens after CMA-banding a hexavalent were formed with six chromosomes having CMA-band. Details of the preparation method for conifer meiotic chromosomes and some cytological applications using the preparations obtained by this method were reported.

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The combination of BA and NAA in concentration at 0-4 mg/l could not significantly induce shoot primordia in four endangered species of orchids. Size of shoot meristem used in the preliminary research might be too big to induce shoot primordia in Grammatophyllum speciosum and for increasing the survival frequency of Vanda and Phalaenopsis. Certain concentrations of BA and NAA affected the survival frequency of Vanda and Phalaenopsis. The type of basal medium has no effect to the growth and the survival frequency of the orchid studied, except for Phalaenopsis gigantea which only grow well in Hyponexpepton medium. The chromosome numbers of the four orchid species showed very high stabilities during the courses of their micropropagations.

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