땅갈이는 농사의 태동기부터 터득되고 실천되는 최초의 농작업 이었다. 동양의 고전들에서도 가장 중요하고 필연적인 농사 기술로 취급되어 왔다. 땅과 하늘의 기운을 소통시키는 성스런 농삿일이기도 하였다. 그러나 땅갈이는 수많은 노동력을 요하는 과정이면서도 그 효과는 방법과 시기, 또는 작물이나 토양에 따라 천차만별로 다르게 나타나는 것이었다. 우리나라의 고대 농서들에 의하면 밭갈이의 실제를 효과에 따라 가급적 가볍게 하려는 쪽으로 검토 · 발전되었다. 그 일환으로 콩과 같은 작물을 밭갈이를 가볍게 하거나 앞 작물의 그루터기에 의존하는 정도로 하고 무경운에 가깝도록 하여도 좋다는 결론에 이르렀다. 이에 더하여 밭갈이는 기존의 잡초를 갈아엎고 파종을 하기 위한 작업 이상의 의미가 없음이 밝혀지게되었다. 또한 제초는 제초제로 쉽게 해결할 수 있는 기술이확립되면서 옥수수나 콩과 같은 작물의 경우, 최소경운이나 무경운 재배법이 체계화되기에 이르게 되었다. 이와 같은 논리는 필자의 무경운재배에 관한 시험연구로도 확증이 되었다. 고대의 밭갈이 농사기술은 이런 경과를 거쳐서 노력의 최소화가능성을 획득하기에 이르렀다.

Characteristics related to grain quality and starch viscosity were investigated in three independent japonica transgenicrice lines expressing a Protox gene from Bacillus subtilis and compared to the control. In this study, we found that there were nosigni

Transgenic rice plants expressing a Bacillus subtilis protoporphyrinogen oxidase (Protox), the last shared enzyme of the porphyrin pathway in the expressed cytoplasm or the plastids, were compared with non-trangenic rice plants in their growth characteristics such as tiller number, plant height, biomass, and yield. Transgenic rice plants of ~textrmT3 generation had 8 to 15 % and 25 to 43% increases in tiller number compared to non-transgenic rice plants at 4 and 8 weeks after transplanting(WAT); similar values were observed for ~textrmT4 generation at 4 and 8 WAT. However, the plant height in both ~textrmT3 and ~textrmT4 generations was similar between transgenic rice plants and non-transgenic rice plants at 4 and 8 WAT. Transgenic rice plants had 13 to 32% increase in above-ground biomass and 9 to 28% increase in grain yield compared to non-transgenic rice plants, demonstrating that biomass and yield correlate with each other. The increased grain yield of the transgenic rice plants was closely associated with the increased panicle number per plant. The percent of filled grain, thousand grains and spikelet number per panicle were similar between transgenic and non-transgenic rice plants. Generally, the growth and yield of transgenic generations (~textrmT2 , ~textrmT3 , and ~textrmT4 ) and gene expressing sites (cytoplasm-expressed and plastid-targeted transgenic rice plants) were similar, although they slightly varied with generations as well as with gene expressing sites. The transgenic rice plants had promotive effects, indicating that regulation of the porphyrin pathway by expression of B. subtilis Protox in rice influences plant growth and yield.

The purpose of this study is to investigate the positive or negative effects of 5-aminolevulinic acid(ALA) on the growth of several crops and weeds, by applying a seed soaking treatment, foliar treatment, and application timing, while comparing biological activity between ALA produced by chemical synthesis (Synthetic-ALA) and extracellularly-accumulated ALA by overexpressing the hemeA gene isolated from Bradyrhizobium japonicum(Bio-ALA). Seed soaking treatment of ALA in barley (five cultivars) and wheat (five cultivars) had not shown positive effects at lower concentrations, 0.05 to 0.5 mM as well as negative effects at higher concentrations, 1 to 30 mM. In rice, there also was no positive effect by seed soaking treatment of ALA at lower concentrations, although the rice became damaged by an application of 5 and 10 mM ALA. Growth in barley cultivars, Ganghossalbori, Naehanssalbori, Songhakbori, Saessalbori, and Daehossalbori were increased up to 14%, 19-51 %, 17-64%, 18-23%, and 22-38% by ALA foliar application at lower concentrations, 0.05 to 0.5 mM, respectively. On the other hand, the growth in barley cultivars was inhibited by ALA foliar application at higher concentrations. Barley responded more positively to ALA foliar application than wheat and rice. The growth stimulation caused by ALA seed soaking treatment was less than by ALA foliar treatment. ALA treatment at the 1.5-leaf stage increased growth of barley by 19-58%, while pretreatment to seeds, post-emergence treatment at 3 days after seeding, 3-leaf stages, and 5-leaf stages had not shown positive effects. Thus, the positive effects of ALA on barley were dependent greatly upon the timing of application and its concentration. Monocots weeds were more sensitive to ALA foliar treatment than dicotyledonous weeds. A monocot weed, Setaria viridis L. was the most susceptible plant to ALA while a dicotyledonous weed, Plantago asiatica L. was the most tolerant. No significant difference in biological activity between bio-ALA and synthetic ALA on barley, wheat, rice, and weed, Ixeris dentate tested was observed. Thus, ALA produced by microorganisms would be a potent substance to be used effectively in agricultural production.

In order to examine the mechanistic basis for differential sensitivities to chilling and subsequent recovery between two rice (Oryza sativa L.) cutivars, a chilling-tolerant japonica type (Ilpumbyeo) and a chilling-susceptible indica type (Taebaekbyeo), changes of physiological responses and antioxidant enzymes were investigated. Both cultivars at 3 leaf stage were exposed at a low temperature of 5~circC for 3 days and subsequently recovered in a growth chamber at a 25~circC for 5 days with 250 mmol m-2 s-1 . Physiological parameters such as leaf fresh weight, relative water content, cellular leakage, lipid peroxidation, and chlorophyll a fluorescence showed that the chilling tolerant cultivar had a high tolerance during chilling. However, the chilling-susceptible cultivar revealed severe chilling damages. The chilling-tolerant cultivar was also faster in recovery than the chilling-susceptible cultivar in all parameters examined. We analyzed the activity and isozyme profiles of four antioxidant enzymes which are: superoxide dismutase (SOD), caltalase (CAT), ascorbate peroxidase (APX), and glutation reductase (GR). We observed that chilling-tolerance was due to a result of the induced or higher antioxidant enzyme system, CAT and APX in leaves and SOD, CAT, APX, and GR in roots. Especially, we observed the most significant differences between the chilling-tolerant cultivar and -susceptible cultivar in CAT and APX activity. Also in isozyme profiles, CAT and APX band intensity in the chilling-tolerant cultivar was distinctively higher than in the chilling-susceptible cultivars during chilling and recovery. Thus, the cold stability of CAT and APX are expected to contribute to a tolerance mechanism of chilling in rice plants. In addition, the antioxidative enzymes activity in roots may be more important than in that of leaves to protect chilling damage on rice plants.

본실험 '식물생장조절제의 콩종자처리가 수향 구성요소간의 상관계수에 미치는 영향'은 식물생장조절제의 콩종자처리가 콩의 초기생육에 어떠한 영향을 주며 이러한 초기영향이 생육후기까지의 지속여부 및 수량 구성요소에 미치는 영향을 연구하기 위한 것이다. 사용한 종자는 Bragg로서 10ppm의 kinetin, ethrel , IAA and salicylic acid에 침지한 후 근류균 인공접종후 파종하였다. 대조구로는 물에 침지한 종자를 사용하였다. 시료는 주기적으로 포장에서 채취하여 초기성장, 근류균형성 생화학적 변화(엽록소함량, Nitrate Reductase활성도) 및 수량 구성요소 등을 보았으며 결과는 다음과 같다. 1. kinetin, IAA 및 Ethrel은 초기생육을 촉진시켰으나 페놀계통의 SA는 발아과정을 지연시켰으며 가장 낮은 발아율을 보였음. 2. kinetin, ethrel, SA는 근류형성을 촉진했으나 IAA는 초기근류형성을 다소 지연시켰으나 후기에는 촉진시켰음. 3. kinetin, ethrel, IAA는 엽록소함량 및 N-RA에 유의성 있는 증가효과를 보였으나 SA는 대조구와 비슷한 경향을 보였음 4. SA는 개화촉진 및 개화수 증가에 가장 효과적이었는데 이는 패놀계통의 화학물질이 작물체의 영양생장에서 생식생장 단계로의 전환을 촉진하고 있음을 보였으며 이러한 생식생장기관의 증대가 수량증대에 기여한 것으로 나타남. 5. 전처리구에서는 수량 및 수량구생요소(꽃수, 협수, 주당립수)가 유의성 있는 증가를 보였으나 협당립수 및 결협률에는 유의성이 없었음 6. 수량은 협수(r=-0.962)와 가장 높은 정의 상관관계를 보였으나 100 립 중과는 부의 상관관계를 보임 (r =-0.634). 7. 100립중의 경우 전 처리구가 대조구보다 낮았는데 이는 식물생장조절제의 처리가 동화생산기관 (source) 및 저장기관(sink)을 동시에 증가시켜 수량증가효과를 가져왔으나 증가된 생산기관(source)이 증가된 저장기관(sink)에 동화물질을 충분히 공급할 수 없음에 따른 동화물질 분배상의 희석 효과(dilution effect)로 보여짐.