Photosynthetic characteristics of spring ephemerals in the desert ecosystem of Dzungaria Basin, northwest China

Abstract

Spring ephemerals have the highest photosynthetic rates in higher plants. Gas exchanges and related environmental factors of four typical spring ephemerals, Eremopyrum orientale, Malcolmia scorpioides, Tetracme quadricormis and Arnebia decumbens were measured in their natural environments in the Gurbantunggut Desert of the Dzungaria Basin, northwestern China. Diurnal variations in net photosynthetic rate (P N ), transpiration rate (E), stomatal conductance (gs), and water use efficiency (WUE) were analyzed at individual leaf level for these species. P N of E. orientale and M. scorpioides showed a bimodal diurnal pattern, whereas that of T. quadricormis and A. decumbens showed a unimodal pattern, with the maximum value occurred at noon (around 12:00). E of all four species showed a unimodal pattern. Higher WUE in the morning was related to higher P N and lower E. The maximum value of gs appeared in early morning, and then decreased gradually during the daytime. The highest photosynthetically active radiation (PAR) occurred at 14:00, but there was a 2 h lag between the highest temperatures of air and leaf and the highest PAR. The maximum net photosynthetic rate (P N max) of the four spring ephemerals were 18.44, 32.03, 33.17, and 20.04 lmolCO 2 m -2 s -1 , respectively. The present study revealed that the midday depression of photosynthesis of E. orientale and M. scorpioides was mainly due to nonstomatal limitation, whereas that of T. quadricormis and A. decumbens was mainly due to stomatal limitation during 14:00-16:00 followed by non-stomatal limitation after 16:00. Our results illustrated that the change of E was consistent with the diurnal fluctuation of air temperature, but the diurnal change of P N was affected by the whole microclimate, i.e. temperature, relative humidity (RH), PAR, etc.

Evapotranspiration partitioning in semiarid shrubland ecosystems: a two‐site evaluation of soil moisture control on transpiration

“…This is especially true of ecosystems with ephemeral plants whose transpiration rates that are typically not measured, as in our study, could significantly increase T/ET at various times during the year (e.g. Yuan et al 2009). …”

Diminished photoinhibition is involved in high photosynthetic capacities in spring ephemeral Berteroa incana under strong light conditions

“…et al, 1979;Lapointe and Lerat, 2006). Ephemerals living in the desert environments are divided into three classes: winter annuals, summer annuals and spring ephemerals according to their growing seasons (Mulroy and Rundel, 1977;Yuan et al, 2009). Ephemerals are important components of the temperate desert flora and part of the pioneer species during the rehabilitation of degraded desert ecosystems.…”

“…They play very important roles in improving the ecological environments (Wang et al, 2003;Shi et al, 2006). As drought-escaping plants, ephemerals living in the desert environments exhibit varieties of special characteristics, such as fast growth and development, short life cycle, strong capability of reproduction and high efficiency of photosynthesis, in order to adapt to the harsh growth environments (Mooney et al, 1976;Ehleringer et al, 1979;Yuan et al, 2009). Photosynthesis is composed of two different processes: the light reaction and carbon fixation.…”

“…Ephemerals have been shown to possess high photosynthetic potential (Ehleringer, 1983;Yuan et al, 2009) allowing fast growth needed for a short life cycle. Ephemerals can sustain very high photosynthetic capabilities and adapt to the severe environmental conditions via different mechanisms.…”

Identification of the best spectral indices to remotely trace the diurnal course of water use efficiency of Tamarix ramosissima in the Gurbantunggut Desert, China

“…Finally, WUE can be measured by assessing the carbon dioxide and water vapor exchange of individual leaves, which are calculated with net photosynthetic rate (P n ) and transpiration rate (T r ) (Glenn et al 1998;Xu et al 2007). These ecological approaches have been used successfully to measure WUE in different terrestrial ecosystems (Blicker et al 2003;Yuan et al 2009). However, field measurements become a problem when such data are needed for a large region over an extended period.…”