液滴体积对水稻叶面接触角的影响

接触角是衡量液滴在水稻叶片上润湿展布效果和滞留能力的主要指标,为了准确测量液滴在水稻叶片表面上接触角(θ)大小,研究了液滴体积对水稻叶面接触角的影响。通过试验测量不同液滴体积下的水稻叶面接触角、液滴高度(h)和液滴接触面直径(d),分析接触角随液滴体积变化的规律。结果显示,液滴体积对4种被测水稻叶面接触角均有显著性影响。在液滴体积上升的初期(1.0~7.5 μL),液滴高度随液滴体积变化的速率(h'_v)与液滴接触面直径随液滴体积变化的速率(d'_v)的比值h'_v/d'_v>h/d,水稻叶面接触角增大;在液滴体积继续上升的后期(7.5~20.0 μL),当h'_v/d'_v≈h/d时,水稻叶面接触角基本不变,当h'_v/d'_v<h/d时,水稻叶面接触角略微减小,最后接触角趋于稳定。由此得出,液滴体积对水稻叶面接触角有显著影响,且接触角的变化趋势与液滴高度和接触面直径及二者的增长速率密切相关。最后还提出了水稻叶面接触角试验统一使用的液滴体积应大于水稻叶面最大接触角所对应的体积,且最好控制在7.5~20.0 μL,水稻叶面最大接触角在液滴体积7.5~10.0 μL、首次h'_v/d'_v≈h/d时近似测得。

Effect of droplet volume on leaf contact angle of rice

Contact angle is the main indicator to measure the effect of droplets on the spreading and retention of rice leaves. In order to accurately measure the contact angle θ of droplets on rice leaf surface, influence of droplet volume on leaf contact angle of rice was studied. The leaf contact angle (θ), droplet height (h) and droplet contact surface diameter (d) of different droplet volumes were measured by experiment, and the variation of contact angle with droplet volume was analyzed. The results showed that droplet volume had a significant effect on leaf contact angle of the four tested rice. At the initial stage of the rise in droplet volume (about 1.0 to 7.5 μL), the ratio of rate at which the droplet height changes with droplet volume (h'_v) to the rate at which the droplet contact surface diameter changes with droplet volume (d'_v)>h/d, leaf contact angle of rice increased. In the later stage of the droplet volume continued to rise (7.5-20.0 μL), when h'_v/d'_v≈h/d, leaf contact angle of rice was basically unchanged. When h'_v/d'_v<h/d, leaf contact angle of rice decreases. Finally, the contact angle tended to be stable. It was concluded that the droplet volume had a significant effect on leaf contact angle of the rice, and the change trend of contact angle was closely related to the droplet height, contact surface diameter and growth rate of both. Finally, it was also proposed that the droplet volume used in the rice leaf contact angle experiment should be larger than the volume corresponding to the maximum contact angle of the rice leaf surface, and it was best controlled within the range of 7.5-20.0 μL. It was also concluded that the maximum contact angle of the rice leaf surface was within 7.5-10.0 μL of droplet volume, and it was approximated when h'_v/d'_v≈h/d for the first time.