Indole 3-acetic acid is a major naturally occurring auxin. Molecular genetics approach using a model plant Arabidopsis have demonstrated the molecular mechanism of auxin action. However, it is still hard to study the physiological role of auxin beyond the model plants. To complement the molecular genetic approach to auxin biology, we have been investigated the chemical probes on auxin signaling and transport, such as antagonist specific for TIR1/AFB auxin receptors, caged auxins and competitive auxin transport inhibitors. Our work substantiates the useful chemical tools for plant biology.

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It is well known that increasing CO_2 concentration stimulates plant photosynthesis at the short-term scale. To understand plant responses to elevated CO_2 concentration at the long-term scale under the field conditions, free-air CO_2 enrichment (FACE) experiments have been conducted for various crop species. The FACE experiments have shown that photosynthetic capacity often, but not always, declined during the prolonged exposure to elevated CO_2, known as an acclimation response. At the whole plant scale, rice biomass was stimulated by elevated CO_2 during the early growth stage, but stimulation ratio gradually decreased with the plant stage. The early growth stimulation could be related with enhanced nitrogen uptake, leaf area expansion and canopy photosynthesis. As the growth stage progressed, a decrease in leaf nitrogen concentration became obvious under FACE conditions, and stimulation ratios of biomass, nitrogen uptake and leaf area were gradually declined. The mechanisms of these acclimation responses are still uncertain, but nitrogen status of the whole plant plays a major role. In addition, the concepts of sink-source or carbon-nitrogen balance are useful for understanding the mechanisms of acclimation response to elevated CO_2, but need to be tested quantitatively by using the FACE systems and mechanistic crop growth models.

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What kind of agriculture is "glutathione agriculture"? "Glutathione agriculture" is a concept of an agricultural effect like the "Green Revolution", in which the function of glutathione is used to increase biomass production. In the present review, we describe how glutathione is used to increase biomass production and compare the agriculture system to the "Green Revolution" effects to overview the research and development for achieving the conceptional vision.

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The mechanism of sex differentiation in cucurbitaceous plants has been studied for more than 80 years. Sex expression in cucumber (Cucumis sativus L.) plants is genetically controlled by the F and M genes. Similarly, it is controlled by the A and G genes in melon (Cucumis melo L.) plants. These genes interact to produce four different sex phenotypes; gynoecious (M-F-) (A-gg), monoecious (M-ff) (A-G-), hermaphroditic (mmF-) (aagg), and andromonoecious (mmff) (aaG-). The gynoecious type produces only female flowers, whereas the monoecious type produces both male and female flowers on the same plant. The hermaphroditic type produces bisexual flowers with both staminate and pistillate organs, while the andromonoecious type produces bisexual and male flowers on the same plant. Sex expression in both cucumber and melon plants is mainly controlled by a plant hormone, ethylene. Thus, the mechanism of sex expression may be similar or even identical in cucumber and melon plants. The F gene was identified more than 10 years ago, whereas the M, A, and G genes were identified recently. The F, M, and A genes encode ACC synthase, which catalyzes the production of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) from S-adenosyl methionine (SAM). This article reviews the similarities and differences in the mechanism of sex expression in cucumber and melon plants and proposes a genetic model of sex expression.

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Rings or arcs of fungus-stimulated plant growth occur often on the floor of woodlands which are commonly called "fairy rings". The fairy-ring forming fungi cause circles of mushrooms, rings or arcs of dark green grass due to luxuriant growth, or rings of dead grass. The liquid-cultured fungus was filtered, the filtrate was fractionated by successive chromatography, and the fractions were tested for their growth regulating activity on bentgrass. This lead to the purification of the active principles, 2-azahypoxanthine (AHX) and imidazole-4-carboxamide (ICA). Both AHX and ICA increased rice seed yield by 25.5% and 26.0%, respectively, in a greenhouse experiment. The growth-promoting activity of AHX was investigated using a rice oligo DNA microarray, reverse transcriptase-polymerase chain reaction, and bioassay. The results indicate that plants develop tolerance to various and continuous stress from the environment and increased nitrogen absorption by AHX-treatment, resulting in the growth promotion.

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Ethylene plays a crucial role in petal senescence in many plant species, and inhibition of ethylene signaling by chemical treatment or genetic modification has successfully improved flower longevity in ornamental plants. In contrast, regulatory mechanisms of petal senescence in flowers that show ethylene-independent senescence remain largely unknown. This report summarizes recent findings focusing on the role of ethylene in petal senescence and our attempts to identify factors regulating ethylene-independent petal senescence.

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Apple latent spherical virus (ALSV) is a latent virus that infects to most host plants without showing any symptoms, has a relatively broad host range, and distributes in the meristematic tissues in infected plants, which are characteristics suitable for virus vector expressing foreign genes in plants. In this article, we showed that the expression of FLOERING LOCUS T (FT) gene from Arabidopsis thaliana by the ALSV vector promoted precocious flowering in several plants including apple, soybean, eustoma, and Japanese gentian. The rapid flowering system described here will be a valuable and powerful tool for efficient breeding of the plants, which have long juvenile period.

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