야간 온도 차이가 생육 및 화색에 미치는 영향을 조사하기 위해 4월 초순 화뢰가 완전히 출현한 다음 화분상태로 자연광이 있는 생장상으로 옮겨 주간/야간 온도를 25/15oC, 25/20oC, 25/25oC로 90일간 달리하 여 처리하였다. 그 후 잎이 노화될 때까지 생육 및 개화특성을 조사하였다. 온도차에 따른 생육특성을 보 면, 25/15oC처리에서 초폭의 수치가 높았으며, 엽내 엽록소함량도 다른 처리에 비해 높았다. 생장상에 입실 후 광합성 속도를 조사한 결과 25/15oC와 25/20oC에 서는 큰 차이 없이 유지되었으나 25/25oC에서는 입실 20일 후 급격히 감소하였다. 25/15oC와 25/20oC에서는 개화기간이 각각 23, 25일로 23일 이상을 유지하였으 나 25/25oC로 야간 온도가 높은 처리구에서는 개화기 간이 13일로 짧았다. 온도차에 따른 개화특성은 주/야 간 온도를 25/15oC로 처리시 화수장이 17.2cm로 가 장 길었고 소화수도 한 화경에 18.2개로 가장 많았다. 화색은 처리 온도차에 따라서 확연히 구분되었는데, 25/15oC에서 화색을 측정한 결과 red를 나타내는 a값 이 37.5로 가장 높았고 화피내 안토시아닌 함량도 2.6mg/100g으로 가장 높은 수치를 보였다.

The tight regulators of fruit set initiation, gibberellin (GA) and auxin, have been applied for decades to induce parthenocarpy, fruit set without fertilization. The integration of GA and auxin signaling mediated by either GA or auxin application during parthenocarpy has been actively reported in tomato, and recently we reported that GA application at pre-bloom also activating auxin signaling and down-regulated negative regulators of fruit set initiation in grapevines. However, the activation of auxin signaling upon GA application without up-regulation of auxin biosynthesis is still unclear. In this study, expression patterns of three auxin efflux transporter genes, VvPIN1a, VvPIN2 and VvPIN4, were monitored during inflorescence development in ‘Tamnara’ grapevines with or without GA application. Without GA application, transcription levels of VvPIN1a and VvPIN4 gradually increased from 14 days before full bloom (DBF) to 2 and 5 days after full bloom (DAF), respectively, except down-regulation of VvPIN1a during 5 DBF to full bloom. However, VvPIN2 expression declined steadily after peaking at 10 DBF. With GA application, VvPIN1a did not show significantly different expression patterns when compared to no GA application, with the exception of 4-fold up-regulation at full bloom, but transcription of VvPIN4 was reduced between 5 and 2 DBF. In addition, VvPIN2 was down-regulated between 12 and 10 DBF by more than 50% compared to levels in the absence of GA application. These reductions of both VvPIN2 and VvPIN4 with GA application prior to pollination suggest that GA application might regulate auxin distribution, instead of auxin biosynthesis, to activating auxin signaling during parthenocarpic fruit initiation.

Gibberellic acid (GA) is a well-characterized plant hormone, which plays a critical role in various plant growth and development. including stem elongation, floral indcution and seed development. GA is known to cause enlargement of ripening fruits and, especially in grapevines, GA shows a unique function: the induction of seedlessness in seeded grape varieties. However, despite extensive previous studies about GA, there has been no clear verification of the mechanism that induces seedlessness in grapes. To understand how GA treatment results in artificial parthenocarpy of seeded grapes at molecular levels, we analyzed transcriptional changes in seeded grapes with and without GA application in various inflorescence developmental stages using RNA-seq. At 14 days before flowering (DBF), seeded grapes were treated with 100 ppm GA and clusters were collected at three developmental stages: 7 DBF, full bloom, and 5 days after flowering (DAF). Of a total of 28,974 genes that were mapped to grape genome reference sequences, 7,013 and 9,064 genes were up- and down-regulated, respectively, in the GA-treated grape as compared to the non-GA-treated control at 7 DBF, full bloom, and 5 DAF. Clustering analysis revealed that these genes could be grouped into 9 clusters with different expression patterns. We also carried out functional annotation based on gene ontology categories. There were significant differences in the expression of the GA and auxin-related gene families. These findings expand our understanding of the complex molecular and cellular mechanisms of GA-induced parthenocarpy of grapes and provide a foundation for future studies on seed development in grapevines.

To study the effects of an urease inhibitor, N-(n-butyl)-thiophosphoric triamide (NBPT), and a nitrification inhibitor, dicyandiamide (DCD), on nitrogen losses and nitrogen use efficiency, urea fertilizer with or without inhibitors and slowrelease fertilizer (synthetic thermoplastic resins coated urea) were applied to direct-seeded flooded rice fields in 1998. In the urea and the urea+DCD treatments, NH4 + -N concentrations reached 50 mg N L-1 after application. Urea+NBPT and urea+ NBPT+DCD treatments maintained NH4 + -N concentrations below 10 mg N L-1 in the floodwater, while the slow-release fertilizer application maintained the lowest concentration of NH4 + -N in floodwater. The ammonia losses of urea+NBPT and urea+NBPT+DCD treatments were lower than those of urea and urea+DCD treatments during the 30 days after fertilizer application. It was found that N loss due to ammonia volatilization was minimized in the treatments of NBPT with urea and the slow-release fertilizer. The volatile loss of urea+DCD treatment was not significantly different from that of urea surface application. It was found that NBPT delayed urea hydrolysis and then decreased losses due to ammonia volatilization. DCD, a nitrification inhibitor, had no significant effect on ammonia loss under flooded conditions. The slow-release fertilizer application reduced ammonia volatilization loss most effectively. As N03 [-10] -N concentrations in the soil water indicated that leaching losses of N were negligible, DCD was not effective in inhibiting nitrification in the flooded soil. The amount of N in plants was especially low in the slow-release fertilizer treatment during the early growth stage for 15 days after fertilization. The amount of N in the rice plants, however, was higher in the slow-release fertilizer treatment than in other treatments at harvest. Grain yields in the treatments of slow-release fertilizer, urea+NBPT+ DCD and urea+NBPT were significantly higher than those in the treatments of urea and urea+DCD. NBPT treatment with urea and the slow-release fertilizer application were effective in both reducing nitrogen losses and increasing grain yield by improving N use efficiency in direct-seeded flooded rice field.field.