The mode of inheritance and allelic relationship of resistance genes in a Korean landrace, Guju and a Korean weedy rice, Geumleungaengmi 33 were studied using Korean isolate (HB9101, race K1) of Xanthomonas oryzae pv. oryzae. The analysis of F₁

Two rice cultivars of the japonica type, ozone-resistant Ilpumbyeo (IL) and ozone-susceptible Keu-mobyeo#l (KM) were exposed to ozone (O3 ) at 0.15 ppm for 30 days. The available nutrient regimes were varied by doubling the supply of nitrogen (N), phosphorus (P) and potassium (K) within a basic fertilizer status (N, P, K; 15, 12, 12 kg l0a-1 ). There was little difference on plant height between ozone-treated and nontreated plants. The most significant ozone stress on tiller number was shown on the 30th day of ozone exposure. Slight recovery from ozone stress was noted on the 60th day. On the 30th day, tiller number was greatly decreased by 40.8% in IL and 64.6% in KM, whereas at a high nitrogen supply regime (2N), it was decreased by 21.4% in IL and 42.7% in KM as compared to the control not treated with ozone at basic fertilizer status. The inhibition of tiller production caused by ozone exposure was alleviated on the 60th day. In both cultivars, number of spikelets per plant and weight of 100 grains were affected little by the ozone treatment irrespective of nutrient regime. However, the number of panicles per plant and yield were reduced significantly. In both cultivars, yield of ozone-treated plants with 2N status was 12.4-16.1 % higher than that of the ozone-treated plants with basic nutrient status. A significant yield decrease of 47.8% and 33.4% was observed for IL and KM, respectively, in ozone-treated plants with higher potassium (2K) status.

Ozone (O3 )-induced changes in chlorophyll content and specific activities of antioxidant enzymes, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were investigated in two rice cultivars (Oryza sativa L.) grown under variable nutrient treatments. For this study, two rice cultivars of Ilpumbyeo (IL) and Keumobyeo#l (KM), which were known as resistant and susceptible to O3 , respectively, were exposed to O3 at 0.15ppm for 30 days and investigated with 10 days interval. The available nutrient regimes were varied by doubling the supply of nitrogen (N), phosphorus (P) and potassium (K) Within a basic fertilizer status (N, P, K; 15, 12, 12kg/l0a-1 ). In both cultivars and at all nutrient status, chlorophyll content in O3 -treated plants decreased with prolonged treatment period, although higher N, P and K supply with O3 treatment alleviated the decrease in chlorophyll content. The activities of almost all enzymes investigated for this study were decreased during initial stages of O3 - exposure except GPX which maintained higher activity throughout the exposure period than the non-treated plant. However, the antioxidant enzymes in O3 -treated plants showed almost the same or higher activities on 30 days after O3 - exposure. The most significant changes in activities were observed in GR of the O3 -treated leaves. With the prolonged treatment period, the activity of GR at 30 days was increased by 3-8 times compared to those in 10 days. Most of the investigated enzymes showed very similar tendency to O3 treatment in all fertilizer status. There was no observed evidence for enhanced detoxification of O3 -derived activated oxygen species in plants grown under higher fertilizer status compared with that in plants grown under basic fertilizer status. The increase in the activities of SOD, APX and GR in rice leaves by relatively long-term treatment with O3 at low concentration is considered to indicate that the plant became adapted to the O3 stress and the protection system increased its capacity to scavenge toxic oxygen species. Our results in two rice cultivars indicated that there was little difference in the activities of antioxidant enzymes between IL and KM, which were known as resistant and susceptible cultivar to O3

To examine the seedling stand and growth as affected by early seeding dates of dry direct seeded rice in the Honam plain area of Korea, Dongjinbyeo was seeded at six seeding dates from early March to late April in rice fields of silty loam soil(Jeonbuk series) at the National Honam Agricultural Experiment Station (NHAES) for two years, 1996 and 1998. Seedling stand decreased slightly. with an early seeding date, but it produced more than the optimum seedling number except for the seeding of 25 March in 1996. Days to emergence was significantly longer, as seeding date was earlier, and days to emergence by early seeding was shortened only by 8 days because the mean air temperature was lower in 1996 than average, while in 1998, the reduction effect was nine to twenty five days because the mean air temperature was higher than average. In early seeding, various weeds occurred at the emergence date of rice and dominant weeds were Alopecurus aequailis, Ludwigia prostata and Rorippa islandica. NH4 + -N content in the soil at the 5th leaf stage and maximum tillering stage were lower, as the seeding date was earlier when nitrogen was split applied as basal and top dressed in 1996, while it was not significantly different among seeding dates when nitrogen was intensively applied as a top dressing in 1998. Tiller number at the maximum tillering stage and panicle number/m2 were more, as seeding date was earlier in 1996, while it was not different in 1998. Filled grain rate and 1,000 grain weight was not different among the seeding dates. Milled rice yield was significantly decreased in the seeding before the middle of March, but in the seeding after late March, it was not varied when compared with the normal seeding date in 1996, while in 1998, there was no difference among seeding dates. From the above results, in consideration of seedling stand, weed occurance, rice growth and milled rice yield, the critical optimum early seeding time in the southern plain area may lie in early April. But it was suggested that when soil moisture is proper for seeding practices, seeding amount is increased and nitrogen is applied after plumule emergence of rice, milled rice yield may not be reduced in the seeding of middle or late March, compared with the seeding in April.l.

콩의 건물축적과 단백질전류에 대한 Source-Sink변경의 효과를 구명하기 위하여 1992년에 고려대학교 자연자원대학 실험농장에서 황금콩을 공시품종으로 착협시기(R3)에 상위 40%, 하위 60%의 엽과 협을 제거하여 건물중 및 단백질함량의 변화를 조사한 결과는 다음과 같다. 1. 상엽-하협제거처리에서 하위 엽과 경 건물중이 증가하였고, 상위 종실과 협 건물중은 감소하였다. 2. 엽의 단백질함량은 상위 엽보다 하위 엽에서 높았다. 3. 종실의 단백질함량은 상엽-하협제거와 하엽-상협제거처리에서 낮았다. 4. 상엽-하협제거처리에서 엽의 단백질함량은 가장 높았고 종실 단백질함량은 가장 낮았다. 5. 본 실험의 결과에서 콩의 단백질원은 하부에서 상부로 이동하나 생식생장기간중의 장거리 전류를 위한 엽 단백질의 재이동은 약한 것으로 나타났다.