Carnations cut in early-bud stage are known to have several advantages for production efficiency （Nowak et al., 1983; Halevy, 1987）, storage and distribution （Goszczy〓ska and Rudnicki 1982）; i.e., less space for storage and shipment （Kofranek, 1976; Halevy et al., 1978）, less damage during postharvest handling, and less susceptibility to ethylene in carnations （Barden and Hanan, 1972; Maxie et al., 1973）. However, many growers hesitated to harvest standard type carnations in an early-bud stage because bud-cut carnations have to be opened before they are sold in the market. In order to retard or avoid deterioration of opened flowers after flower bud opening （FBO）, the time required for FBO of cut flowers must be reduced. Several methods using specific chemical solutions to drive FBO of bud-cut carnations have been reported （Kofranek, 1976; Goszczy〓ska and Rudnicki, 1982）. However, little attention has been paid to the physical environment, such as light intensity, for post-harvest FBO of 'tight bud'-cut carnations. Also the addition of inorganic nutrient salt （INS）, as in use of hydroponic culture, for post-harvest bud opening has not been reported previously. The flower heads and leaves/stems of cut carnations play a role as a sink or a source for carbohydrates. Considering the significance of carbon balance during post-harvest FBO, CO2 exchange measurement of flower heads and leaves/stems is necessary under elevated PPFD conditions. The aims of the present experiments were to investigate the time required for FBO of 'tight bud'-cut carnations by high PPFD and an addition of INS in flower opening solution, and the relationship between carbon/water balance and cut carnations quality during/after FBO of 'tight bud'-cut carnations.

Red standard carnations （Dianthus caryophyllus L cv. Francesco） that had been harvested at 'tight bud' stage [stage III as defined by Cywi〓ska-Smoter et al. （1978）] in Yamaguchi （Ex-1）, and Nagano （Ex-2, 3） were used. The stems cut-ends of the carnations （n=60） were trimmed to a length of 45cm （Ex-1） and 60cm （Ex-2, 3） in deionized water and separated randomly for FBO treatments. For each FBO treatment, carnations were placed in a transparent cylindrical container [0.33 m in diameter, 0.50 m in height （Ex-1） and 0.70 m in height （Ex-2, 3）], set in a growth chamber, with number of air exchanges of 128 l h-1 （Ex-1）, 180 l h-1 （Ex-2）, 25.7 l h-1 for flower heads space and 154.3 l h-1 for leaves/stems （Ex-3）. Cut carnations were placed under PPFDs [30 （P30）, 120 （P120）, and 250 （P250） μmol m-2 s-1 for Ex-1, 30 （P30）, 150 （P150） μmol m-2 s-1 for Ex-2, and 30 （P30）, 90 （P90） and 150 （P150） μmol m-2 s-1 for Ex-3] at a bud top level with continuous light from white fluorescent lamps. Air temperature and relative humidity in the containers were controlled at 25・1°C and 87・5% during FBO. Seven （Ex-1, 2） or six （Ex-3） cut carnations were placed in 50 ml of flower opening solution containing 25 mg l-1 AgNO3 + 200 mg l-1 8-hydroxyquinolin-citrate （8-HQC） [with 30 g l-1 sucrose （S30） or without sucrose （S0） for Ex-1, and with INS in flower opening solution （INS） and without INS （N） for Ex-2]. We tested some FBO treatments of P30-S30, P120-S30 and P250-S30 for Ex-1, P30-INS, P30-N, P150-INS, and P150-N for Ex-2, and P30, P90, and P150 for Ex-3. All Experiments were repeated twice. After FBO, the stems of cut carnations were re-cut in distilled water and placed in deionized water in a chamber （20・1°C） with a 12 h photoperiod at 12 μmol m-2 s-1 PPFD for 10 d in order to evaluate flower quality. The 5 scores were used for quality evaluation of treated carnations depending on visual quality （Fujiwara et al., 2004）. These experiments had been carried out until 6 out of 7 buds （Ex-1, 2） or 5 out of 6 buds （Ex-3） in each treatment were opened more than 75o, which is equivalent to Stage VII according to Cywi〓ska-Smoter et al. （1978）. CO2 exchange rate, dark respiration rate, sucrose uptake, flower opening angles and transpiration rate were measured in all experiments. Total net CO2 exchange （TNCE）, integrated gross photosynthesis （IGP）, total sucrose uptake （TSU） and total carbon uptake （TCU） rate were calculated for understanding the relationship between FBO/flower quality and these factors.

Among the S30 treatments, the higher the PPFD, the more rapidly the flowers opened. The average periods required for FBO were 6.75, 6.5, 6.0, and 7.0 d for P30-S30, P120-S30, P250-S30 and P250-S0, respectively （Ex-1）. Flowers in the S30 treatments were considered as satisfactorily marketable products. These results indicate that PPFD of 120 and 250 μmol m-2 s-1 combined with 30 g l-1 sucrose in flower opening solution was effective for reducing the time required for post-harvest FBO of 'tight bud'-cut carnations.

Although there was no significant difference in flower-opening angle between INS and N treatments during FBO, bud-cut carnations in both experiments tended to open more rapidly in INS treatments （Ex-2）. Cut carnations absorbed more flower opening solution at the INS treatment during FBO treatment because absorbed INS would decrease water potential of petals. Mean flower quality scores were high （4.0） at the end of all FBO treatments （Ex-2）. To ascertain the relationship between INS and FBO, the amount of each component of the absorbed INS should be investigated. Addition of an optimal concentration, or a different constituent of INS in the flower opening solution may further accelerate FBO of 'tight bud'-cut carnations. Carnations under P150 treatments stored greater quantity of carbohydrates than those in P30 treatments, by the end of FBO. Greater TCU resulted from increased TSU and TNCE under higher PPFD, which also contributed to reduce the time for FBO of 'tight bud'-cut carnations. Hourly average of TSU in P150 treatments, which is proportional to the uptake of flower opening solution, was twice as much as that in P30 treatments, indicating that under higher PPFD transpiration increased. 'Tight bud'-cut carnations placed under high PPFD （P150） did not show stem blockage or water deficiency during FBO even though they were cut. FBO of 'tight bud'-cut carnations by higher PPFD could be accelerated by increased rates of TSU and TNCE, stimulated by the addition of INS. Enhancing TCU will improve FBO of 'tight bud'-cut carnations, help them retain their quality after opening.

Gross photosynthesis of bud-cut carnations were increased in higher PPFD treatment and water balance was kept positively during FBO, showing that flower opening solution uptake of cut carnations was greater than amount of transpiration during FBO treatment （Ex-3）. Absorbed sucrose in petals could be hydrolyzed with glucose or fructose and these monosaccharides would decrease the water potential in cells of petals. Cells will be expanded and cut carnations will open rapidly. FBO of 'tight bud'-cut carnations correlated with fresh weight increment of them with correlation coefficients of 0.80 for P30, 0.78 for P90, and 0.89 for P150 treatment during FBO treatment （Ex-3）. The mean flower quality scores of opened carnations after FBO closely correlated with TCU with correlation coefficients of 0.94 and 0.98 during 10-d flower quality evaluation. The elevated PPFD shifted the climacteric peak ahead under the same temperature condition. Even though the climacteric peak was shifted ahead in higher PPFD treatment, their quality for 10 d after FBO was better than that in lower PPFD treatment. Present proposed FBO technique might be applied to other kinds of cut flowers, depending on the physiological and morphological characteristics.

The high PPFD combined with 30 g l-1 sucrose and an addition of INS in flower opening solution was effective for reducing the time required for FBO of 'tight bud'-cut carnations, maintaining their high quality during/after FBO. FBO of 'tight bud'-cut carnations correlated with fresh weight increment （opening solution uptake）, and the mean flower quality scores of opened carnations after FBO closely correlated with TCU during 10 d flower quality evaluation. High PPFD showed beneficial effects on positive carbon/water balance for post-harvest FBO of 'tight bud'-cut carnations and preservation of flower quality after FBO. Though the climacteric peak of cut carnations was shifted ahead by increasing PPFD, carnations quality after FBO in higher PPFD was better than that in lower PPFD treatments. These results showed that the positive carbon/water balance by elevated PPFD reduced the time required for FBO of 'tight bud'-cut carnations, and contributed to the preservation of their quality.

カーネーションのつぼみ切りは、開花後の収穫に比べて、生産効率、貯蔵・流通での小容量化、物理的衝撃への耐性、エチレン耐性などの点で優れている。しかし、つぼみ切りカーネーションは、市場に出荷する前に強制的に開花させなければならない。品質の劣化を避けるためには、強制開花の時間はできる限り短縮することが必要である。しかし、つぼみ切り切り花の強制開花に関する既往の研究には、光強度などの物理的環境要素に関するものや、開花液への無機塩添加の影響に関するものはほとんどない。つぼみ切り切り花の開花には、切り花の炭素収支・水収支が関係しているはずであるが、そのような解析例もない。そこで、本研究では、光合成有効光量子束密度（以下、PPFD）と開花液への無機塩添加の強制開花所要時間および切り花の品質への影響を、切り花の炭素収支・水収支との関係も含めて解析することを目的とした。

本研究での一連の実験は、基本的に同じ仕様に基づいている。つぼみ切りカーネーションは透明な円筒容器に入れ開花処理をした。照明は連続照明とした。各カーネーションの茎の切り口を開花液に差し込み、開花液にはショ糖の添加／無添加、および無機塩の添加／無添加の処理区を設けた。開花処理後、10日間栽培し、品質を評価した。開花処理期間中は炭素収支・水収支に関連する事項の測定を行った。以後の記述で、Pの後の数字は連続照明時のPPFDの値（単位：〓mol m-2 s-1）を、Sの後の数字は開花液中のショ糖の濃度（単位：g l-1 ）を、INSは開花液に無機塩を添加した場合を、Nは添加しなかった場合を表す。

得られた結果は以下のようである。

S30区のなかでは、PPFD（P30―P250）が高いほど開花時間は短縮された。また、INS区は開花時間を短縮する傾向がみられた（有意差はない）。INS区の切り花はＮ区に比べ開花液を多く吸収していた。

P150区での開花処理期間中の総炭素吸収量はP30区に比べ顕著に大きかった。これは、総ショ糖吸収量、総二酸化炭素吸収量（純同化量）ともに、高いPPFD下で大きくなったからである。総ショ糖吸収量が、高いPPFD下で大きくなったのは、蒸散が促進されたためである。P150区の時間平均のショ糖吸収速度は、P30区のおよそ2倍であった。

開花処理期間中の開花液吸収量は蒸散量よりも多かった。すなわち、水収支は正であった。開花の進行（開花角度の増加）と生体重の増加は正の相関があった。一方、開花後の品質は、開花処理期間中の総炭素吸収量と正の相関があった。

高いPPFDはクライマクテリックピークの時期を早めた。しかし、クライマクテリックピークが早くなったが、品質保持は低PPFDの場合より良好であった。

以上、本研究はつぼみ切りカーネーションの強制開花の環境制御に関して、これまでほとんど考慮されることのなかった光強度および開花液への無機塩添加に注目し、高いPPFDおよび無機塩添加が強制開花時間を短縮するとともに、開花後の品質保持にも貢献することを見出し、その効果のメカニズムを、切り花の炭素収支および水収支の観点から考察したものであり、学術上および応用上貢献するところが少なくない。よって、審査委員一同は、本論文が博士（農学）の学位論文に値するものと認めた。