본 연구는 각시괴불나무 종자의 휴면유형과 발아특성을 구 명하기 위하여 수행되었다. 수분흡수 실험결과, 각시괴불나무 종자는 수분흡수가 원활히 이루어졌다. 따라서, 물리적 휴면은 가지지 않는 것으로 판단된다. 각시괴불나무 종자는 탈리 시점에 미숙배를 가지고 있으며, 발아직전까지 배/종자 비율이 약 46% 증가하였다. 온도실험결과, 5℃에서는 발아가 전혀 이루어지지 않았다. 20℃에서는 파종 후 1주부터 발아가 시작되었으며 최종 발아율은 2주차에 86.7%였다. 15℃에서는 파종 후 2주부터 발아를 시작하였으며, 최종 발아율은 4주차에 75.0%였다. 25℃에서 파종 후 1주부터 발아가 시작되었으며 최종 발아율은 19주차에 48.3%였다. 결론적으로, 각시괴불나무 종자의 발아를 위한 최적온도는 가장 높은 최종 발아율과 가장 짧은 평균 발아 일수를 나타낸 20℃이다. 각시괴불나무 종자는 5℃를 제외 한 모든 온도에서 4주 이내에 발아하였기 때문에 생리적 휴면은 관찰되지 않았다. 따라서, 각시괴불나무 종자는 오직 형태적 휴면만을 가지는 것으로 판단되었다.

Osmoconditioning and hardening effects for the seed germination of normal and naturally aged rice seeds were studied through analyzing the total sugars and α -amylase activity. The normal seeds which used to have high germination rate accelerated germination with the osmoconditioning at the suboptimal temperature of 17~circC . On the other hand, the aged seeds did not affect germination rate at 25~circC , while increased germination rate and accelerated germination a little at 17~circC , Hardening of aged seeds increased germination rate by 10-15% compared with control seeds at both 17 and 25~circC and accelerated germination. Total sugar content and α -amylase activity of normal seeds were higher than did aged seeds. The aged seeds with treatment of osmoconditioning and hardening increased total sugar content and α --amylase activity, but hardening was more effective than osmoconditioning. The α --amylase activity was positively correlated with the total sugar content and germination rate.

In order to determine the optimum harvest time of vegetable corns, the changes in sugars, soluble solids, and flavor of kernels of sweet (cv. ‘Golden Cross Bantam 70’), super sweet (cv. ‘Cocktail E-51’), and waxy corns (cv. ‘Chalok 2’) were observed at different ripening stages. Sucrose was a major sugar in the sweet and super sweet corns and the content increased from 15 to 21 and 27 days after silking (DAS), respectively and then decreased. Glucose and fructose contents of sweet and super sweet corns tended to decrease with kernel maturity. Total sugar content of the sweet corn analyzed by the anthrone method increased rapidly from 15 to 21 DAS, while that of the super sweet and the waxy corns increased slowly up to 24 and 26 DAS, respectively and decreased thereafter. The content of soluble solids in sweet corn was much higher than that of super sweet corn. Starch content of the sweet corn increased slowly from 15 to 33 DAS, while that of the super sweet corn increased a little rapidly from 15 to 21 DAS and then leveled off to 33 DAS. Starch content of the waxy corn increased continuously from 21 to 38 DAS. There was a positive correlation between the sum of individual sugars (sucrose, glucose, and fructose) and soluble solids in both sweet and super sweet corns, while the content of soluble solids was not related to the sum of individual sugars or total sugars. The flavor rate of sweet and super sweet corns maintained high between 21 and 27 DAS and that of waxy corn decreased from 24 to 33 DAS. The optimum harvest time for sweet, super sweet, and waxy corns was thought to be 21 to 24 DAS considering sugar and starch contents, flavor, and marketing.

An experiment was carried out to find out the changes in morphology, sugars, and α -amylase activity during the priming of rice seeds (Oryza sativa L. cv. ＇Ilpumbyeo＇). For priming, seeds were soaked in -0.6 MPa PEG solution at 15~circC for 4 days (properly primed) and at 25~circC for 4 and 10 days (over-primed) and dried at room temperature. The size of coleoptile and differentiated leaves of properly primed seeds were bigger and coleoptile was separated from the other part of embryo compared with non-primed and over-primed seeds. As priming of seeds advanced, compound starch grains in the endosperm disintegrated into tiny starch granules, and small holes were found in the tiny starch granules and a cavities developed between embryo and endosperm. The radicle and plumule of properly primed germinating seeds developed faster than non-primed and overprimed germinating seeds. Sucrose, maltose, and raffinose contents of properly primed seeds decreased, while content of glucose and fructose and α -amylase activity increased. However, sugar content and α -amylase activity of over-primed seeds were lower compared with non-primed seeds or properly primed seeds.

priming; rice seed; SEM; embryo; starch granule; α -amylase; sugar

An experiment was carried out to find out the priming effects of rice seeds, Oryza sativa L. (cv. Ilpumbyeo) on. the seedling establishment and early emergence under excess soil moisture conditions. Seeds were primed by soaking in -0.6 MPa polyethylene glycol (PEG) solution at 25~circC for 4 days. The primed seeds were sown in soils with various soil moistures (60, 80, 100, 120, and 140% field capacity) at 17 and 25~circC , respectively. Germination and emergence rates, plumule height, and radicle length of primed seeds were higher than those of untreated seeds at any soil moisture and temperature examined. The time from planting to 50% germination (T50 ) of primed seeds was less than that of untreated seeds by 0.9～3.7 days. Germination rate, emergence rate, plumule height, and radicle length were highest at the soil moisture of 80% field capacity among the soil moistures. Priming effects of rice seeds on germination and emergence rates were more prominent under the unfavorable soil moistures (60, 100, 120, and 140% field capacity) than those under the optimum soil moisture condition (80% field capacity). However, priming effects on seedling growth were greater at near optimum soil moisture compared with too lower or higher soil moistures. Therefore, these findings suggest that priming of rice seeds may be a useful way for better seedling establishment under the adverse soil conditions.

To find out the effects of humidification and hardening of rice (Oryza sativa L. cv. Ilpumbyeo) seeds on the germination, both normal and artificially aged seeds with 60% germination rate were humidified at 40, 60, and 80% RHs and 25~circC for five weeks or hydrated for 6, 12, 18, and 24 hours at 25~circC from one to five cycles for hardening. Relative humidity and duration of humidification did not affect the germination rate of normal seeds, while reduced the time to get 50% germination rate (T50 ) by 1.0～1.6 days compared to that of normal seeds at 25~circC . Aged seeds humidified at 40 and 60% RHs did not affect the germination rate and T50 regardless of relative humidity and duration of treatment, while at 80% RH, the germination rate decreased and T50 increased significantly with the duration of humidification. Hardening of normal seeds reduced T50 by 0.7～1.1 days without changes in the germination rate. However, the germination rate and T50 of aged seeds soaked in water for 6, 12, and 18 hours were similar regardless of soaking/drying cycles, while hardening of artificially aged seeds with 1～4 cycles in 24 hours soaking increased the germination rate by 11-16% and reduced T50 by 1.4～2.0 days.

Experiments were carried out to find out the optimum water potential, temperature, and duration for the priming of rice seeds, Oryza sativa L. (cv. Ilpumbyeo) for better germination at sub-optimal temperatures. Seeds were primed in 0, -0.2, -0.4, -0.6, -0.8, and -1.0 MPa PEG (polyethylene glycol) solutions at 25~circC . The optimum water potential for seed priming, the highest water potential at which rice seeds did not germinate, was -0.6 MPa. To find out optimum priming temperature and duration rice seeds were primed in -0.6 MPa PEG solution and 0 MPa (water as a control) for various durations at 15 and 25~circC and the seeds were germinated at 17, 20, and 25~circC . Considering germination rate and speed, the optimum priming time in water (0 MPa) was 4 days at 15~circC and 1 day at 25~circC , while 4 days was the optimum priming time in a -0.6 MPa PEG solution, regardless of the priming temperature. Priming reduced the actual time of germination, especially at sub-optimal temperatures. Priming did not affect germination rate in -0.6 MPa PEG solution at 15~circC , but overpriming reduced the final germination rate in water at 15~circC and in -0.6 PEG solution at 25~circC . Total sugars and α -amylase activity induced during the seed priming were negatively correlated with the final germination rate and there was no noted relationship with the speed or uniformity of germination.