Influence of Drought on Leaf Growth and Water Potential in Tobacco

한발이 담배 잎의 생장과 수분 포텐셜에 미치는 영향

The experiment which imposed the water stress to tobacco(Nicotiana tabacum L.) plant was carried at the late of maximum growth period. In order to know the influence of drought stress on the growth and developmemt of tobacco leaves of different position and to elucidate the physiological response of plant to various soil water content, stomatal conductance, and leaf water potential were measured. The drought stress at the maximum growth period negatively affected to the overall growth characteristics of shoot. The response of the growth was small at the middle and the lower leaves, and great at the upper leaves. The relative water content of upper, middle, and lower leaves at the fifth day after treatment were 74, 64, and 59%, respectively, as soil water content was reduced by 4.3%. This suggested that the wilting point of tobacco leaf was about 75%. The leaf water potential was -0.58 MPa in control and dropped to -1.20 MPa at the fifth day after treatment. This indicated that wilting of leaf may occur at the condition in which the difference of water potential between treatment and control, well watered, was greater than about 20%. Stomatal conductance at the fifth day after treatment dropped from 12 mol /$\textrm{m}^2 sec^{-1}$ to 0.8 mol /$\textrm{m}^2 sec^{-1}$ in the middle and the upper leaves. Stomatal conductance of lower leaves already matured were not affected highly by drought stress at the maximum growth period, but maturing leaves, middle and upper leaves, were highly affected by limitation of soil water.

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 /$\textrm{m}^2 sec^{-1}$에서 0.8 mol /$\textrm{m}^2 sec^{-1}$로 떨어져, 한발처리에 따른 담배의 최대생장후반기의 엽위에 따른 생장반응은 중ㆍ상위엽까지 영향을 미쳤다.