Photosynthetic responses of Populus przewalski subjected to drought stress

Abstract

Cuttings of P. przewalski were exposed to two different watering regimes which were watered to 100 and 25 % of field capacity (WW and WS, respectively). Drought stress not only significantly decreased net photosynthetic rate (P N ), transpiration rate (E), stomatal conductance (g s ), efficiency of photosystem 2 (PS2) (F v /F m and yield), and increased intrinsic water use efficiency (WUE i ) under controlled optimal conditions, but also altered the diurnal changes of gas exchange, chlorophyll fluorescence, and WUE i . On the other hand, WS also affected the P N -photosynthetically active radiation (PAR) response curve. Under drought stress, P N peak appeared earlier (at about 10:30 of local time) than under WW condition (at about 12:30). At midday, there was a depression in P N for WS plants, but not for WW plants, and it could be caused by the whole microclimate, especially high temperature, low relative humidity, and high PAR. There were stomatal and non-stomatal limitations to photosynthesis. Stomatal limitation dominated in the morning, and low P N at midday was caused by both stomatal and non-stomatal limitations, whereas non-stomatal limitation dominated in the afternoon. In addition, drought stress also increased compensation irradiance and dark respiration rate, and decreased saturation irradiance and maximum net photosynthetic rate. Thus drought stress decreased plant assimilation and increased dissimilation through affected gas exchange, the diurnal pattern of gas exchange, and photosynthesis-PAR response curve, thereby reducing plant growth and productivity.

Effects of water stress and nitrogen supply on leaf gas exchange and fluorescence parameters of Sophora davidii seedlings

“…P N , g s , C i , ambient CO 2 concentration (C a ), and PAR were measured at 07:00, 09:00, 11:00, 13:00, 15:00, 17:00, and 19:00 on a fully sunny day (September 3, 2006) under natural conditions to determine diurnal variation of gas exchange. Intrinsic water use efficiency (WUEi) was calculated by dividing P N by g s , and stomatal limitation value (L s ) was calculated using the following formula: L s = 1 -C i /C a according to Yin et al (2006). P N -PAR response curves were measured at 1 800, 1 500, 1 200, 1000, 800, 500, 200, 100, 50, 20, and 0 μmol(photon) m -2 s -1 of PAR under uniform conditions (25 °C, 330-350 μmol(CO 2 ) mol -1 , and 71-75 % RH) at 10:00-11:30 on two sunny days (September 5 and 7, 2006).…”

“…Mass of the pot plus seedling at field capacity was adjusted accordingly. Chl fluorescence was determined on fully expanded exposed leaves (one leaf each plant) using a modulated fluorometer (PAM 2100, Walz, Effeltrich, Germany) on September 2, 2006 according to Roháček and Barták (1999) and Yin et al (2006). Initial fluorescence (F 0 ) and maximal fluorescence (F m ) were measured after a 30-min dark adaptation.…”

Changes in photosynthesis, chlorophyll fluorescence, and antioxidant enzymes of mulberry (Morus ssp.) in response to salinity and high-temperature stress

“…The stomatal limitation value (Ls) was calculated using the formula Ls = 1 -Ci/Ca (where Ca is atmospheric CO2 concentration), in accordance with Yin et al (2006). Linear regressions of irradiance and PN over the range of 0-200 µmol photons of photosynthetically active radiation (PAR) m −2 s −1 were applied to determine the apparent quantum yield (AQY) of carbon assimilation (Yin et al 2006).…”

Growth and potential reproduction of Poa crymophila in response to season precipitation shortage in the Eastern Tibetan Plateau, China

“…Drought reduced above and below ground biomass (Table 3), and finally resulted in small plant, our results agreed with Casper's results (1996). Drought reduced plant productivity, because of plant increasing dissimilation and decreasing assimilation through affecting gas exchange, the diurnal pattern of gas exchange, photosynthesis PAR (photosynthetically active radiation) response curve, net photosynthetic rate, stomatal conductance, the maximal efficiency of PSII photochemistry, the actual quantum yield and the photochemical quenching (Williams and Black, 2004;Folkard et al, 2005;Yin et al, 2006). However, Llorens et al (2004) also found that draughted plants (Erica multiflora and Calluna vulgaris) were able to maintain higher leaf photosynthetic rates than control plants in relation to the accumulated rainfall over the months previous to the measurements.…”