Soybeans [Glycine max (L.) Merr.] are frequently exposed to unfavorable environments during growing seasons and water is the most important factor limiting for the production system. The purpose of this study was to determine the leaf water potential changes by irrigation, and to evaluate the relationships of leaf water potential, growth and yield in soybeans. Three soybean cultivars, Hwangkeumkong, Shinpaldalkong 2, and Pungsannamulkong, were planted in growth chamber and field with irrigated treatments. Leaf water potential of three soybean cultivars was positively correlated with leaf water content during vegetative and reproductive growth stages in growth chamber and field experiments. Leaf water potentials measured for three soybean cultivars under growth chamber were higher than those of under field conditions. Higher leaf water potential with irrigated plots under field was observed compared to conventional plots during reproductive growth stages. Leaf water potentials of three soybean cultivars were continually decreased during reproductive growth stages under field and there was no significant difference among them. Number of leaves, leaf water content, pod dry weight, number of seeds and seed dry weight with irrigated plots were higher than those of conventional plots. The results of this study suggested that leaf water potential could be used as an important growth indicator during the growing season of soybean plants.

Plant water status during growth is directly and indirectly associated with seed yield. The objective of the present study was to determine the genotypic differences in leaf water characteristics at an early growth stage of soybean [Glycine max (L.) Merrill] plants through the pressure-bomb technique. Measurements of water potential as well as relative water content (RWC) were made at the third leaf from the fully-expanded top leaf of eight different soybean genotypes grown for 31 to 35 days after field emergence. On the basis of the modified exponential model, pressure-volume (PV) curves were fitted well (R2 =0.92＊＊ to 0.99＊＊ for the curvi-linear region and R=0.67＊＊ to 0.96＊＊ for the linear region), indicating that a segmented model using PROC NLIN of SAS could be used effectively to estimate the leaf water characteristics. The regression analysis for the pressure-volume (PV) curve revealed genotypic variation in the solute potential at saturation (Ψs,sat :-10.7 to -14.8 bar), solute potential at incipient plasmolysis (Ψs,ip : -14.3 to -18.3 bar), RWC at incipient plasmolysis (RW Cip : 83.3 to 91.7%), high integrated turgor pressure from saturation to plasmolysis ( 1 b : 0.39 to 0.81), and maximum volumetric modulus of elasticity (~varepsilon max : 150 to 445 bar).).

본 실험은 담배의 최대생장 후반기에 수분제한처리를 하여, 한발이 엽위에 따라 생장과 발달에 미치는 영향을 분석하고, 엽영에 따른 엽내 수분상태가 기공컨덕턴스, 잎수분포텐셜과 토양수분관계에 영향을 미치는 생리적 반응을 구명하고져 실시하였다. 담배의 최대생장기 한발영향은 지상부의 제형질을 감소시켰고, 엽위에 따른 생장반응은 중ㆍ하위엽에서 작았고 상위엽에서 컸다. 처리 5일째에 잎의 상대수분함량은 토양수분함량이 4.3%로 감소될 때 상위엽 74%, 중위엽 64%, 하위엽 59%로 담배잎의 위주점은 상대수분함량이 약 75%이었다. 한발에 따른 잎수분포텐셜은 대조구의 -0.58 MPa에서 처리구의 처리5일째에 -1.20 MPa로 떨어졌고, 대조구와 비교하여 약 20%의 수분포텐셜차이가 위주점이 되었다. 기공컨덕턴스는 중ㆍ상위엽에서 12 mol /m2 sec1에서 0.8 mol /m2 sec1로 떨어져, 한발처리에 따른 담배의 최대생장후반기의 엽위에 따른 생장반응은 중ㆍ상위엽까지 영향을 미쳤다.

Development of shoot and root, leaf water potential and photosynthetic rate affected by water stress in early growing stage of tobacco were surveyed to interpret stress response in terms of plant physiological and agricultural aspects. The growth of shoot and root was highly suppressed by water stress and the difference in dry weight by rewatering was smaller in root than in shoot. The total root length was highly decreased by water stress and the lengths of root for water stress and non-stress were 74m and 84m, respectively, after rewatering. The root growth treated by water stress was increased between 2nd and 3rd day after treatment indicating that temporary water stress at early growing stage might have increased of root zone activity for early growth stage. The leaf water potentials were decreased to -7.63MPa, -9.47MPa, -11.89MPa, -13MPa at the 2nd, 3rd, 4th and 5th day by water stress. The relative water contents were 75%, 62% and 57% at the 3rd, 4th and 5th day after treatment. Photosynthesis was reduced largely by water stress. The photosynthetic rate after treatment at 2nd day and 3rd day was dropped to 18.15~mu mol. CO2 /m2 ㆍsec-1 and 9.35~mu mol. CO2 /m2 ㆍsec-1 . It was never recovered to the normal, even after rewatering. Stomatal conductance had been reduced since 2nd day after treatment and increased after rewatering.

콩품종 타치나가하(Tachinagaha)를 공시하여 토양수분조건에 따른 식물체내의 수분상태 즉 잎의 수분 potential, 광합성 및 생육에 미치는 영향을 검토하고자 실험을 수행한 결과를 요약하면 다음과 같다. 1. 광량자밀도가 1,000u mol m2 s1 이하로 낮아질 때 광합성 속도는 점차 저하하였고, 토양수분 조건에 따른 광합성 속도는 건조구와 과습구는 적습구보다 떨어졌다. 2. 생육시기에 관계없이 광합성 속도와 기공 conductance와는 정의 상관 관계가 인정되었다. 3. 광합성 속도와 기공 conductance는 토양수분 부족에 매우 민감하게 반응하였다. 4. 잎의 수분 potential은 적습구가 과습구 또는 건조구보다 높았으며, 광합성 속도와도 밀접한 관련이 있었다. 5. 잎의 신장은 토양수분에 민감한 반응을 보여 건조구에서 엽면적이 가장 낮았으나 엽록소 함량은 높았다. 6.식물체의 총 건물중은 적습구 > 과습구 > 건조구 순이었으나 건물중에 대한 뿌리의 비율은 건조구에서 높게 나타났다