植(zhi)物(wu)氣(qi)(qi)(qi)孔(kong)(kong)計(ji)(ji)用(yong)來定量(liang)測量(liang)各種因素對葉片氣(qi)(qi)(qi)孔(kong)(kong)行為的影響，可方便、重(zhong)復、準(zhun)確地計(ji)(ji)算出(chu)氣(qi)(qi)(qi)孔(kong)(kong)阻(zu)抗、氣(qi)(qi)(qi)孔(kong)(kong)導度和蒸(zheng)騰速率，還可測得空氣(qi)(qi)(qi)溫(wen)濕(shi)度，葉面(mian)溫(wen)度，光合有(you)效輻射。因此植(zhi)物(wu)蒸(zheng)騰速率的測量(liang)對于農業科研、教(jiao)學、園藝研究(jiu)(jiu)、林業研究(jiu)(jiu)等具(ju)有(you)重(zhong)大意義(yi)。

　　植物(wu)葉片氣(qi)孔(kong)(kong)(kong)是(shi)植物(wu)體水分散失和(he)光合作(zuo)用(yong)所需CO2進入的(de)(de)通道。氣(qi)孔(kong)(kong)(kong)特(te)性(xing)是(shi)植物(wu)生(sheng)理(li)生(sheng)態狀態的(de)(de)一個十分重(zhong)要的(de)(de)指標，它(ta)對于研究植物(wu)物(wu)種的(de)(de)特(te)性(xing)和(he)環(huan)(huan)境因(yin)子，如土壤水分狀況、太陽(yang)輻射(she)強度、污染物(wu)對植物(wu)的(de)(de)影(ying)響(xiang)具有重(zhong)要價值。競道植物(wu)氣(qi)孔(kong)(kong)(kong)計用(yong)來定量測(ce)量各種因(yin)素對氣(qi)孔(kong)(kong)(kong)行(xing)為的(de)(de)影(ying)響(xiang)，可方(fang)便、重(zhong)復、準(zhun)確(que)地計算出氣(qi)孔(kong)(kong)(kong)阻力。根據循環(huan)(huan)擴(kuo)散原理(li)，由植物(wu)葉片表面濕度的(de)(de)變化來進行(xing)測(ce)量計算。

　　氣(qi)(qi)(qi)孔(kong)(kong)是(shi)植(zhi)(zhi)物(wu)進行(xing)體(ti)(ti)內外氣(qi)(qi)(qi)體(ti)(ti)交(jiao)(jiao)換(huan)的主要(yao)場所。水蒸(zheng)汽(qi)、CO2、O2都要(yao)共(gong)用氣(qi)(qi)(qi)孔(kong)(kong)這(zhe)個通道，對應植(zhi)(zhi)物(wu)的蒸(zheng)騰、光合、呼(hu)吸過程。氣(qi)(qi)(qi)孔(kong)(kong)導度(du)植(zhi)(zhi)物(wu)體(ti)(ti)內外的氣(qi)(qi)(qi)體(ti)(ti)交(jiao)(jiao)換(huan)速率(lv)(lv)與(yu)植(zhi)(zhi)物(wu)體(ti)(ti)與(yu)氣(qi)(qi)(qi)體(ti)(ti)的接(jie)觸(chu)面(mian)積成正比(bi)。氣(qi)(qi)(qi)孔(kong)(kong)結構(gou)大(da)(da)大(da)(da)地增加了葉(xie)細胞與(yu)氣(qi)(qi)(qi)體(ti)(ti)的接(jie)觸(chu)面(mian)。氣(qi)(qi)(qi)孔(kong)(kong)張(zhang)開時一般長約7~30um，寬約1~6um。而進出氣(qi)(qi)(qi)孔(kong)(kong)的CO2和H2O分(fen)子的直徑分(fen)別約為0.46nm和0.54nm，因(yin)而氣(qi)(qi)(qi)體(ti)(ti)交(jiao)(jiao)換(huan)暢通。氣(qi)(qi)(qi)孔(kong)(kong)越密集，則有(you)效面(mian)積就越大(da)(da)，氣(qi)(qi)(qi)體(ti)(ti)交(jiao)(jiao)換(huan)速率(lv)(lv)就越快(kuai)。植(zhi)(zhi)物(wu)通過氣(qi)(qi)(qi)孔(kong)(kong)的開閉來控制氣(qi)(qi)(qi)體(ti)(ti)交(jiao)(jiao)換(huan)速率(lv)(lv)，直接(jie)影響蒸(zheng)騰、光合、呼(hu)吸等過程。

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