The present invention without requiring a power source, a simple structure, and to be able to adjust the atmosphere such as the internal temperature. A to the upper surface 2a of the transparent cover body 2 which covers the seedlings 1 I provide a ventilation unit 3. The ventilation unit 3, a valve member 5 for opening and closing the mouth 4 for ventilation are opened on the top surface 2a of the cover body 2, and I is formed by the operating device 6 of the valve member 5. The operation unit 6 is provided with a shape memory alloy member 6a for operating the valve member 5 can be deformed by the heat energy of sunlight. The shape memory alloy member 6a, I is housed in an upright in a transparent form of case 7 is formed on the upper surface 2a of the cover body 2. [Selection Figure] Figure 1【課題】 電源を必要とすることなく、簡易な構造で、内部温度等の雰囲気を調節できるようにする。【解決手段】 苗1を覆う透光性のカバー本体2の上面2aに換気部3を設ける。この換気部3を、カバー本体2の上面2aに開口されている換気用の口4を開閉する弁部材5と、この弁部材5の動作装置6とで形成する。この動作装置6は、太陽光の熱エネルギーで変形して弁部材5を動作させる形状記憶合金部材6aを備える。この形状記憶合金部材6aを、カバー本体2の上面2aに起立状に形成している透明状のケース7に収納する。【選択図】 図1
