Carbon dioxide depletion within the plant canopy in growing egetable grops
Carbon dioxide depletion within the plant canopy in growing egetable grops
复制标题
正在生长的蔬菜中植物冠层内的二氧化碳消耗
DOI：
10.2503/jjshs.39.185
复制
发表时间：
1970
影响因子：
--
通讯作者：
Tadashi Ito
中科院分区：
文献类型：
--
作者：
Tadashi Ito
通过红外气体分析仪测量蔬菜生长中的二氧化碳浓度，以讨论二氧化碳消耗，二氧化碳消耗被认为是充分光合作用的严重问题之一。偶尔用自动设定箱控制的抽气泵以每分钟 0.3 升的速度通过分布在植物内部和上方的塑料管抽取气体采样。 在露天场地，晴天有风和无风时测得的树冠内最低 CO2 浓度分别为 275-285ppm 和 205-250 ppm。这种损耗是由平均风速低于 1.5m/sec 引起的。在玻璃和塑料房子下面的大气中，二氧化碳的短缺比外面更显着。清晨，树叶和土壤呼吸积累的大量二氧化碳可用于光合作用。然而，很快，内容就低于环境水平。因此，增加 dC/dt 的临界光强度可以假设为植物顶部的 3-5 klux。最后，如果通风口保持关闭，CO2 浓度降至 80-85ppm。在阳光明媚的日子，当植物在塑料大棚中生长良好时，对 CO2 分布的测量表明，每天两次观察到 CO2 消耗，通风前后均如此。在第一次消耗中，CO2 水平下降到接近 105ppm，最低浓度 (Zm) 的高度出现在植物高度的中部。当脊通风机开到最大25cm时，第二次消耗略有减少，浓度保持在140ppm。另一方面，通风机大大防止了CO2消耗，并且在很宽的株高范围内观察到Zm。为了防止顶篷内特定部分的二氧化碳耗尽，在早上通风口保持关闭的情况下运行空气循环风扇。距风扇 8m 处的所得轮廓表明，它对植物内部和上方的 CO2 均匀化没有影响。CO2 消耗也受到叶面积密度的很大影响。覆盖乙烯基薄膜的苗床空气中浓度降至65-70ppm。高叶面积密度延长了通风之前的平衡时间过程。所有这些观察结果表明，通风速度和叶面积密度是晴天覆盖条件下 CO2 消耗的主要因素。有人可能会说，通过保持通风机打开，可以避免二氧化碳消耗。然而，N.A.R.与通风率的曲线表明，在商业玻璃和塑料温室中，每小时温室容积换气20-30次，不足以使植物冠层内的二氧化碳供应不足以进行充分的光合作用。从实际角度讨论了第一次二氧化碳消耗期间二氧化碳富集的有益效果。
CO2 concentrations in vegetable growing were measured by means of an infra-red gas analyser in order to discuss the CO2 depletion, being considered as one of serious problems for sufficient photosynthesis. Sampling gas was taken occasionally with suction pump controlled by automatic setting box at the rate of 0.3 litre per minute through the plastic tube distributed within and above the plants.In the open field, minimum CO2 concentrations within the canopy measured on a clear day with and without wind were 275-285ppm and 205-250 ppm. This depletion was caused by mean wind speed below 1.5m/sec. over the plants and by dense plant community.In the atmosphere under the glass- and plastic-houses, CO2 shortage was more remarkable than that outside. High CO2 accumulated by leaf and soil respiration was avaiable for photosynthesis in the early morning. Very soon, however, the content fell below ambient. Thus, critical light intensity for increasing dC/dt could be assumed to be 3-5 klux on the plant top. Finally, CO2 concentration fell to 80-85ppm provided the vents remained closed.Measurements of the CO2 profile at the time when plants were well grown in a plastic-house on a sunny day, showed that CO2 depletion was observed twice a day, before and after ventilation. In the first depletion CO2 level dropped to nearly 105ppm and the height of minimum concentration (Zm) was found at the middle part of plant height. When ridge ventilator was opened toa maximum of 25cm, the second depletion was slightly decreased and the concentration remained at 140ppm.On the other hand, a ventilating fan prevented greatly CO2 depletion and Zm was observed over a wide range of plant height. To prevent the CO2 depletion in the particular part within the canopy, air circulating fan was operated in the morning when the vents were keeping closed. The resulting profile 8m away from the fan, showed that it had no effect on CO2 homogenization in and above the plant.CO2 depletion was also greatly affected by leaf area density. The concentration in the air of nursery bed covered with vinyl film was depleted to 65-70ppm. High leaf area density lengthened the time course of equilibrium until ventilated.All of these observations indicate that the ventilation speed and leaf area density are the predominant factors for the CO2 depletion under covered conditions on a sunny day. It may be argued that by keeping the ventilators open CO2 depletion would be avoided. The curves of N. A. R. against the ventilation rate, however, would suggest the air changes of 20-30 times for house volume per hour often occurred in commercial glass-and plastic-houses are not enough CO2 supply within the plant canopy for sufficient photosynthesis.Beneficial effect of CO2 enrichment during the first CO2 depletion was discussed from practical point of view.