호접란의 저온 기간 중 간헐적 고온처리에 따른 개화 억제

학위논문 (박사) -- 서울대학교 대학원 : 농업생명과학대학 식물생산과학부, 2020. 8. 김기선.Phalaenopsis plants require low temperature exposure for their inflorescence initiation. However, since they are originated from tropical regions where a temperature is steadily warm without photoperiodic change throughout the year, this low temperature requirement is dissimilar to the low temperature requirements of vernalization-requiring plants which demand prolonged cold exposure as shown in a typical winter. In this study, we conducted a series of experiments to figure out the low temperature requirement and to determine the inhibitory effects of discontinuous low temperature exposure by intermittent high temperature in Phalaenopsis. In Chapter I, the periods of low temperature exposure required for floral induction were observed at different cultivars and temperatures, and the effect of discontinuous low temperature exposure by intermittent high temperature treatment was also determined. In Chapter II, the correlation between inflorescence initiation and carbohydrate contents in the leaves was analyzed at different inducing temperatures. In Chapter III, metabolic changes under intermittent high temperature condition were identified by transcriptome analysis. In this study, six to eight weeks of low temperature exposure were required to induce the competent inflorescence emergence regardless of cultivars. Also, there was no difference between the required periods at 20 and 23˚C. These results indicated that the low temperature accumulation for floral induction did not show a quantitative response to inducing temperatures although a certain period of low temperature is necessary for the inflorescence initiation of Phalaenopsis. Also, in Chapter II, a delay of inflorescence emergence was observed in the plants at 17˚C compared with at 20˚C and 23˚C. The inflorescence initiation induced the carbohydrate accumulation in the leaves, while the plants at vegetative temperature showed significantly low carbohydrate contents. The inflorescence emergence was correlated with the photosynthetic ability and soluble sugar contents in the leaves at each temperature, not the amount of the cumulative low temperatures. Low temperature disrupted by intermittent high temperature treatment significantly inhibited the inflorescence initiation despite sufficient low temperature period. Flowering-inhibited plants showed the increased number of new leaves, implying that vegetative growth was maintained by the intermittent treatment. In transcriptome analysis, down-regulation of carbohydrate metabolism was observed. Also, the expression levels of genes related to carbohydrate metabolism such as orthologs of fructose-1,6-bisphosphatase, glycoside hydrolase, G-3-P dehydronase, and sucrose transporter were decreased by intermittent high temperature treatment rather than continuous low temperature treatment. These levels were similar under continuous high temperature and intermittent high temperature conditions. Also, homologs of genes related to flowering, PhalCOL and DhGI1, showed decreased expression levels under continuous or intermittent high temperature conditions. Sugar contents in the leaves significantly increased under continuous low temperature condition rather than continuous high temperature condition. However, the contents were significantly decreased under intermittent high temperature condition rather than continuous low temperature condition although the contents were higher than under continuous high temperature condition. These results indicated that discontinuous low temperature exposure by intermittent high temperature treatment might induce the down-regulation of sugar metabolism and inhibit the subsequent inflorescence initiation of Phalaenopsis plants. In conclusion, Phalaenopsis plants showed carbohydrate accumulation in the leaves during inflorescence initiation. The inflorescence emergence timing was correlated with carbohydrate contents rather than the amount of low temperature exposure. Low temperature exposure disrupted by intermittent high temperature prevented the inflorescence initiation despite sufficient low temperature exposure and these inhibitory effects would be attributed to the down-regulation of carbohydrate metabolism by intermittent high temperature condition.호접란의 화경 유도를 위해서는 저온 노출이 필요하다. 하지만, 호접란은 일장의 변화가 없고 일년 내내 따뜻한 열대 지역에 자생하는 식물이라는 점이 특징이다. 이러한 특징은 겨울의 연속적인 저온 노출을 필요로 하는 일반적인 춘화 식물들의 특징과는 다르다. 따라서, 본 연구에서는 호접란의 저온요구도를 이해하고 불연속적인 저온 노출 환경에서의 개화 억제 효과를 알아보고자 하였다. 제1장에서는 호접란의 화경유도를 위해 필요한 저온 노출 기간을 여러 품종 및 저온 처리 온도에서 확인하였으며, 또한 간헐적 고온 처리를 통한 불연속적인 저온 노출 환경에서의 화경유도 반응을 관찰하였다. 제2장에서는 화경유도와 잎에서의 탄수화물 함량 간의 상관관계에 대하여 분석하였으며, 제3장에서는 전사체 분석을 통한 간헐적 고온 처리 환경에서의 대사 변화를 확인하였다. 본 연구에서는 호접란의 화경유도를 위해서는 품종에 상관없이 6~8주 동안의 저온 노출 기간이 필요하였으며, 저온 기간이 부족할 경우 화경이 출현하지 않거나 화경 발달이 멈추는 현상이 관찰되었다. 20℃와 23℃의 저온 처리에서는 화경유도 반응에 차이가 없었으며, 이를 통해 화경유도를 위한 저온 충족 반응이 처리 온도에 양적인 반응을 나타내지 않는다고 판단되었다. 두번째 연구에서 17℃의 저온 처리를 하였을 때 20℃나 23℃에 비해 화경 출현이 유의성 있게 늦게 나타났다. 저온에 의해서 화경이 유도될 때 영양생장 환경과 비교하여 잎에서의 탄수화물 축적이 일어나는 것을 관찰할 수 있었는데, 이는 각 온도에서의 화경 출현 일수는 그 온도에서의 광합성 능력과 잎에서의 당 함량과 상관관계가 있었다는 것을 나타낸다. 따라서 호접란의 화경유도는 저온의 양 보다는 유도 환경에서의 탄수화물 함량이 중요한 것으로 나타났다. 간헐적 고온 처리로 인한 불연속적인 저온 노출 환경에서 저온 노출 기간이 충분했음에도 불구하고 화경유도가 억제되었고 이때 신엽의 수가 유의성 있게 증가하였는데, 이를 통해 영양생장이 유지되었음을 알 수 있었다. 전사체 분석을 통해 간헐적 고온 처리 환경에서의 탄수화물 대사의 저하를 확인하였고, fructose-bisphosphatase, glycoside hydrolase, G-3-P dehydrogenase orthologs의 발현량이 감소하였다. 또한 호접란의 개화 관련 유전자들의 발현을 비교하였을 때 연속적 고온 또는 간헐적 고온 처리 환경에서 연속적 저온 환경에 비해 PhalCOL과 DhGI1 homolog의 발현이 감소하였고, DhEFL4 homolog의 상대적인 발현이 증가하였다. 이러한 유전자들의 발현량은 연속적 고온과 간헐적 고온 환경에서 유사한 것으로 나타났다. 당의 함량을 확인하였을 때 연속적 저온 환경에서 앞선 실험과 마찬가지로 높게 유지되었다. 간헐적 고온 환경에서는 연속적 고온 환경에 비해 당 함량이 높았고, 연속적 저온 환경에 비해서는 유의성 있게 낮았다. 이러한 결과는 간헐적 고온 처리로 인한 호접란의 화경유도 억제가 탄수화물 대사의 저하로 인한 잎에서의 당 함량 감소 때문일 수 있음을 의미한다. 따라서, 호접란의 화경유도 과정에서 잎에서의 탄수화물 축적이 일어나며, 화경유도는 저온의 양 보다는 각 온도에서의 당 함량과 상관관계가 있음을 알 수 있었다. 불연속적인 저온 노출은 호접란의 화경유도를 억제하며, 이러한 개화억제 효과는 탄수화물 대사의 저하로 인한 것으로 판단된다.GENERAL INTRODUCTION 1 LITERATURE REVIEW 5 Horticultural Characteristics of Phalaenopsis 5 Environmental Requirements for Inflorescence Initiation of Phalaenopsis 7 Metabolic Changes during Inflorescence Initiation of Phalaenopsis 8 LITERATURE CITED 11 CHAPTER I. Low Temperature Requirement for Inflorescence Initiation and Flowering Inhibition by Intermittent High Temperature Treatment in Phalaenopsis 17 ABSTRACT 18 INTRODUCTION 20 MATERIALS AND METHODS 23 RESULTS 27 DISCUSSION 35 LITERATURE CITED 39 CHAPTER II. Correlation between Inflorescence Initiation and Carbohydrate Contents in the Leaves at Different Inducing Temperatures in Phalaenopsis 42 ABSTRACT 43 INTRODUCTION 45 MATERIALS AND METHODS 48 RESULTS 53 DISCUSSION 63 LITERATURE CITED 69 CHAPTER III. Flowering Inhibition by Carbohydrate Reduction in the Leaves by Intermittent High Temperature Treatment in Phalaenopsis 74 ABSTRACT 75 INTRODUCTION 77 MATERIALS AND METHODS 81 RESULTS 88 DISCUSSION 98 LITERATURE CITED 105 CONCLUSIONS 112 ABTRACT IN KOREAN 114Docto

고온 교란을 이용한 팔레놉시스의 겨울철 조기 개화 억제

학위논문 (석사)-- 서울대학교 대학원 : 식물생산과학부, 2015. 2. 김기선.High temperature above 28°C is necessary to inhibit flowering in Phalaenopsis. During winter season, however, growers maintain a greenhouse temperature conditions below 25°C because of greenhouse heating cost. This cultivation practice induces premature flowering. This study was conducted to develop new cultivation strategy by preventing premature flowering through energy-saving flowering inhibition using high temperature inhibition. The experiment in Chapter I was performed to determine the growth period of the juvenile stage and low temperature duration required for inducing premature flowering. Clones of Phalaenopsis Hwasu 355 grown in a greenhouse for 2, 4, and 8 months (2, 4, and 8-month-old), which have 1-2, 2-3, or 3-4 newly developed leaves, respectively, were used in the experiment for determining the juvenile period. These plants were grown under low temperature at 25/20°C with 7 different durations: 0, 1, 2, 3, 4, 5, and 10 weeks. After each treatment, plants were transferred to 28/28°C. In addition, to observe flower-stalk differentiation 8-month-old plants were treated with 7 weeks of low temperature. With the results of chapter I, the objective of the experiment in Chapter II was to determine the cultivation strategy for inhibition premature flowering by high temperature inhibition. Clones of 8-month-old Phalaenopsis Hwasu 355 and Doritaenopsis Mantefon plants were cultivated at four different temperature regimes for 16 weeks: continuous low temperature (L) (no interruption), 1 week of high temperature (H) every 1 week (1L + 1H), 1 week of high temperature every 2 weeks (2L + 1H), and 2 weeks of high temperature every 2 weeks (2L + 2H). During the experiment, the low temperature and high temperature were set at 25/20°C and 28/28°C, respectively. In Chapter I, the length of juvenile period of Phalaenopsis plants seemed to be between 4 and 6 months, with 3 fully developed leaves. Low temperature for 4 and 5 weeks could induce flower-stalk emergence in 8-month-old Phalaenopsis Hwasu 355, but the elongation of flower-stalks stopped. About 8 weeks of low temperature was required to induce visible inflorescences (flower-stalks longer than 0.5 cm). In chapter II, the inhibition of premature flowering was observed in plants treated with high temperature interruption treatments. However, the flowering was slightly inhibited in Doritaenopsis Mantefon, whereas that was completely inhibited in Phalaenopsis Hwasu 355. The inhibition effects increased with shortening the interval between high temperature interruption treatments. The number of days to visible inflorescence increased with lengthening the duration of total high temperature. These results indicate that high temperature interruption can prevent premature flowering in winter. Furthermore, high temperature interruption can be used to improve previous cultivation practice through raising the flower quality by preventing premature flowering. However, because the low temperature sensitivity is different among cultivars, detailed studies are needed for specific cultivars.CONTENTS ABSTRACT i CONTENTS iv LIST OF TABLES vi LIST OF FIGURES vii GENERAL INTRODUCTION 1 LITERATURE REVIEW The juvenility of orchids 4 Flowering in response to low temperature in orchids 4 Inhibition of premature flowering in Phalaenopsis 6 LITERATURE CITED 7 CHAPTER I. Determination of Juvenile Period and Low temperature Duration to induce Premature Flowering in Phalaenopsis ABSTRACT 11 INTRODUCTION 13 MATERIALS AND METHODS 15 RESULTS 18 DISCUSSION 24 LITERATURE CITED 27 CHAPTER II. Inhibition of premature flowering of Phalaenopsis orchids by high temperature interruption ABSTRACT 29 INTRODUCTION 31 MATERIALS AND METHODS 34 RESULTS 37 DISCUSSION 46 LITERATURE CITED 49 ABSTRACT IN KOREAN 52Maste

Effect of Ground Freezing with Liquid Nitrogen on Freezing Rate and Mechanical Properties of Coastal Clayey Silt

The artificial ground freezing (AGF) method is an environmentally friendly ground improvement technique for numerous geotechnical applications. It can be used in fine-grained soils, which may not be efficiently improved via conventional cement-based ground improvement techniques. However, some of the issues hindering the application of the AGF method to fine-grained soils include inefficiency in achieving the target volume of frozen soil and degradation in mechanical properties of the soil after the freezing-thawing process. In this paper, the freezing rate and degradation in strength and stiffness of a clayey silt in South Korea were investigated using field experiments. At two different outlet temperatures (-180 degrees C and -120 degrees C), liquid nitrogen was injected into the freezing pipe to evaluate the freezing rate. A simple equation to estimate the theoretical radial freezing rate was proposed and compared with the experimental results. In addition, a piezocone penetration test (CPTu) and pressuremeter test (PMT) were performed to assess the degradation in strength and stiffness of the soil after the freezing-thawing process. Results of the CPTu, PMT, and laboratory experiments revealed that the degradation in mechanical properties of Korean clayey silt could be attributed to the rearrangement of soil particles. (C) 2021 American Society of Civil Engineers