Some Questions And Error Analysis About Measurement Of Gas Exchange In Leaf Photosynthetic Rate

To analyze the questions and errors occurred in measuring the leaf Photosynthetic rate using Gas exchange, instrumental error, observation error and biology error in the use of portable photosynthesis system were computed and analyzed.The results show that instrumental error in open system is more than 8%. The main error is owing to CO2 analyzer and flowmeter. And instrumental error in closed system is more than 1.5%. The main error is owing to CO2 analyzer. Error is decided in the level of photosynthesis both of them. Comparatively, the instrument error of open system is bigger than that of closed system especially under the lower photosynthesis. Furthermore, choosing the right leaf chamber and the reasonable measurement of leaf area is important especially.The errors caused by environment factors during the comparable measurement of leaf photosynthesis are big especially in the morning and evening, and increase rapidly along with extension of the metrical duration. The error caused by the change of radiation is more than 40% in the morning and evening, and is less than 5% in the rest time. The error caused by the change of temperature fluctuates obviously from 20% to 40%. But it is less than 10% about 8 am and 14 pm. The error caused by the change of CO2 concentration is relative steady from 10% to 20%. In one word, the error caused by environment factors from 8 am to 14 pm is less and more steady than in other time. But the errors caused by change of environment factors in short time is less than 5%.The error caused by different part of one leaf is from 10% to 40%, and bigger than that caused by different leaves. When the change of radiation environment has instantaneous change, the Photosynthetic rate can't reach the rate that it should be in the changed situation. That is called the photoperiodic induction. Usually the time of the photoperiodic induction is from 3 minute to 8 minute. The error caused by the photoperiodic induction changes along with the initiatory and terminative radiation level. And the effect of Photosynthetic oscillations should be emphasized in fast measurement of photosynthesis.