Lettuce (Lactuca sativa L.) is known to contain water-soluble substances that are biologically active. Aqueous or methanol extracts and residues from leaves of lettuce plants were assayed to determine their allelopathic effects, and the causative allelochemicals from fractions were quantified by means of HPLC analysis and bioassayed. Extracts from oven-dried leaf samples were more phytotoxic than those from freeze-dried samples. Leaf extracts of 40 g L-1 were completely inhibitory on root growth of alfalfa (Medicago sativa L.), while root growths of barley (Hordeum vulgare L.) and soybean (Glycine max L.) were less sensitive. Early seedling growth of both alfalfa and barnyard grass (Echinochloa crus-galli) was significantly reduced by methanol leaf extracts. The major allelopathic substances analyzed by HPLC were coumarin, trans-cinnamic acid, o-coumaric acid, p-coumaric acid and chlorogenic acid. Of them p-coumaric acid was found as the greatest amount (8.9 mg 100 g-1 ) in the EtOAc fraction; only coumarin was found in all the fractions. Hexane and EtOAc fractions of L. sativa reduced alfalfa root growth more than did BuOH and water fractions. These results suggest that lettuce had potent herbicidal activity, and that its activity differed depending on type and amount of causative compounds by fraction.

Scented lettuce (Lactuca sativa L.) may be highly valued in certain lettuce growing areas, and the trait may be useful as a marker for genetic studies in lettuce. Crosses were made between the scented cultivar ‘Baimach’ and the nonscented cultivar ‘Oaklea

돈분뇨 발효액비를 양채류인 결구상추의 재배에 비료원으로 활용하면서 환경오염 부담을 경감하고자 강원도 고랭지 지역인 대관령에서 수행한 연구결과를 요약하면 다음과 같다. 돈분뇨 발효액을 토양에 처리하였을 때 대조구인 화학비료시용구에 비해서 결구상추의 생육이 증가하는 경향을 보였으며, 수량은 돈분뇨 발효액 처리구에서도 저농도인 50배 희석구에서 가장 높았다. 돈분뇨 발효액 처리시 결구상추에 흡수되는 영양소 함량은 대조구인 화학비용시용구에 비해 증가되는 경향이었으며, 돈분뇨 발효액 희석구와 비교할 때 유의성있는 차이를 보여주지 않았다. 시험전 토양에 비해 돈분뇨 발효액를 처리한 후 pH, EC, 토양의 질소(NH4-N, NO3-N), Av. P2O5, Ex. Ca 및 Mg함량은 뚜렷한 변화가 없었다. 본 시험결과 돈분뇨 발효액에는 많은 양의 비료성분을 함유하고 있어 과다 시용시에는 작물피해는 물론 토양이나 지하수를 오염시킬 수 있기 때문에 결구상추의 경우 관비재배시 50배 희석하여 시용하면 작물생육과 환경 측면에서 매우 바람직하다고 판단되었다.

Nitrate in edible vegetables is converted to nitrite by nitrate reductase(NR) and/or bacteria in intestines. Nitrite and amino, in the intestine of some animals and human, bind to form nitrosamine, which is toxic and known as carcinogen. This study was carried out to examine the effect of added chlorides and their concentrations on growth, yield and nitrate content in leaf lettuce plants in hydroponics. Seeds of lettuce cv, "Samsunjokchukmyon" were planted on April 29, and seedlings were planted on June 2, and were cultured until July 5 in 1998. KCI and CaCl₂ were used as chloride source and their concentrations were 1, 2 and 4 me/L, respectively, in the lettuce standard nutrient solution for National Horticultural Research Institute(NHRI). Completely randomized design with 3 replications was used. Nitrate content and NR activity were measured 2 and 5 weeks after planting(WAP). The obtained results were summarized as the follows : Leaf weight per plant was difference from harvest dates and treatments, but total leaf weight was not significantly different among treatments. Number of leaves was higher in KCI 2 me/L, CaCl₂1 me/L and control at 2 WAP than the others, and was higher in KCI 1 me/L, and control at 3 WAP than others, and was higher in control at 5 WAP. Total number of harvested leaves was the highest in control with 14, which followed by KCI 2 me/L and CaCl₂1 me/L. Nitrate content was decreased by addition of chloride in nutrient solution. Nitrate content in the 3rd and 9th leaves was significantly decreased. NR activity was higher in control and CaCl₂ addition treatments, while KCI addition treatments reduced NR activity. However, no direct relationship with nitrate was observed. Growth characteristics such leaf length and leaf width were not significantly influenced by chloride addition.

An efficient regeneration system was established by using in vitro plantlets of germinated seedlings from different cultivars of lettuce (Lactuca sativa cv. Chongchima, Chongchuckmyun, Jeokchima, Jeokchuckmyun). Shoot formation were observed from all cultivars on MS medium supplemented with 0.1 mg/L NAA and 0.5 mg/L BA. In all cultivars, when cotyledon was cultured, the number of shoot per explant was more greater than that hypocotyl and leaf disc were cultured. Shoot formation rate (91.7%) was high in a cotyledon culture of cultivar, Chongchukmyun. The growth of multiple shoots derived from the cultivar, Chongchukmyun, was most effective on medium containing 0.5 mg/L BA and 1.0 mg/L GA3. When shoots were transferred on MS medium without plant growth regulators, roots were effectively differentiated. Rooted plantlets were acclimated on pots for further propagation.

비파괴적인 방법으로 활력이 높은 종자를 선별하는 방법을 개발하기 위하여, 참깨, 파, 상추 종자를 상대습도 90%, 온도 45℃ 에서 인위적으로 퇴화시켜 활력이 다른 종자를 물에 침지하였을 때 종자가 분비하는 당, 아미노산, 단백질의 양과 속도 등을 조사한 결과를 요약하면 다음과 같다. 1. 참깨 종자는 활력과 침지시간에 관계없이 당, 아미노산, 단백질을 거의 분비하지 않았다. 2. 파의 죽은 종자는 건전종자나 활력이 중인 종자보다 아미노산을 더 많이 분비하였으나 전당과 단백질 분비량은 크지 않았다. 3. 상추의 죽은 종자는 당, 아미노산, 단백질을 모두 많이 분비하였다. 건전종자와 활력이 중인 종자는 당은 거의 분비하지 않았으나 아미노산과 단백질은 다소 많이 분비하였다.