Co-Authors:
Atias, M., Inst. of Agric. Engineering, Agric. Res. Organization, Volcani Center, POB 6, Bet-Dagan 50250, Israel
Teitela, M., Inst. of Agric. Engineering, Agric. Res. Organization, Volcani Center, POB 6, Bet-Dagan 50250, Israel
Barak, M., Inst. of Agric. Engineering, Agric. Res. Organization, Volcani Center, POB 6, Bet-Dagan 50250, Israel
Cohen, S., Inst. of Soil, Water and Environmental Sciences, Agric. Res. Organization, Volcani Center, POB 6, Bet-Dagan 50250, Israel
Schwartz, A., Robert H. Smith Inst. of Plant Sci. and Genetics in Agric., Fac. of Agric., Food and Envir. Quality Sciences, Hebrew Univ. of Jerusalem, POB 12, Rehovot 76100, Israel
Abstract:
High levels of solar radiation and vapor pressure deficit are common during the summer in Mediterranean greenhouses, leading to high evapo-transpiration rates and crop water use. In these conditions, the ability to measure and predict transpiration is an important factor in determining irrigation application rates. In addition, tools for accurate estimation of photosynthetic rates can be useful for several purposes, e.g. estimation of plant production, examination profitability of carbon enrichment in greenhouses and improving climate control. We examined the possibility to estimate instantaneous average crop transpiration and photosynthesis by using an open chamber approach. This approach is practical in a fan-ventilated greenhouse. The rate of transpiration and photosynthesis of Capsicum annuum var. Selica was measured during spring and summer 2007 in a greenhouse at the Besor experimental station in southern Israel. The rate of transpiration was measured by six lysimeters, each with two plants, and calculated by multiplying the difference in humidity ratio between greenhouse air outlet and inlet by the air flow rate through the greenhouse. Photosynthesis was measured on several plants with a gas exchange system (LI-COR, LI-6200) and was calculated by multiplying the difference in CO 2 concentration between air inlet and outlet by the air flow rate through the greenhouse. Results showed good agreement between the two methods used for calculating transpiration and photosynthesis. The daily average transpiration measured by the open chamber approach and by the lysimeters respectively were 263±32 and 273±38 W m -2 (where ± denotes 95% confidence interval). Midday photosynthesis values were 8.1±1.3 and 10.3±1.6 μmole m -2 s -1, respectively, with the open chamber calculation and the LI-6200 analyzer. The results suggest that the average crop transpiration and photosynthesis can be estimated with good accuracy from measurements of air water vapor content and CO 2 concentration at the inlet and outlet of a fan-ventilated greenhouse. The data also show that the open chamber approach responds rapidly to instantaneous changes in solar radiation that influence both photosynthesis and transpiration.
תפריט נגישות
ניגודיות עדינה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
איפוס הגדרות נגישות
להורדת מודול נגישות חינם
