It decides,b1b2b3b4 whether or not it measures the generation frequency of the elastic wave which is generated the frame (2,2,2,2) the elastic wave reception component which is locked (11a, 11b, 11c and 11d) with, by cavitation, respectively at front and back of change of the water stress, for the vascular bundle plant at front and back of change from generation frequency of the elastic wave which was respectively measured, it calculates the rate of change of generation frequency, from the rate of change which was calculated, it has reached to the level which cannot restore enborizumu of vascular bundle system, it includes the affusion time to the vascular bundle plant and the fact that water content is decided this decision result as a collimating mark.軸部(2b1,2b2,2b3,2b4)に固定された弾性波受信素子(11a,11b,11c,11d)により、キャビテーションにより発生する弾性波の発生頻度を、維管束植物に対する水ストレスの変化の前後でそれぞれ測定し、変化の前後でそれぞれ測定された弾性波の発生頻度から、発生頻度の変化率を算出し、算出された変化率から、維管束組織のエンボリズムが修復できないレベルに達しているか否かを判定し、この判定結果を指標として、維管束植物への灌水時期及び灌水量を決定することを含む。
