三种孑遗植物近地保护与迁地保护中的光合生理差异与生长适应性比较

The"near situ conservation"and"ex situ conservation"were important measures to save rare and endanged plants and very small populations of wild plants in the past.In order to ascertain the differences in growth adaptability and photosynthetic characteristics between near situ and ex situ conservation of three relic plants--Tetraena mongolica and Ammopiptanthus mongolicus and Zygophyllum xanthoxylon in west Ordos.The diurnal variation characteristics of photosynthesis of three relic plants in near situ and ex situ conservation experimental site were measured simultaneously by the LI-6400XT photosynthesis apparatus,and the interaction between environmental factors and photosynthetic characteristics was analyzed.The growth and survival differences among different plant species in the conservation experimental site were compared with the monitoring data of environmental factors such as weather and soil.The results show that:(1)There were obvious differences in habitat characteristics between near situ and ex situ conservation experimental site.The average annual growth amount,growth potential and wintering survival rate of Tetraena mongolica and Ammopiptanthus mongolicus in the near situ conservation experimental site were much higher than those in the ex situ conservation experimental site.There were no significant differencebetween near situ and ex situ conservation experimental site of Zygophyllum xanthoxylon.(2)The net photosynthetic rate of three relic plants in different experimental sites were showed a"bimodal"curve.The net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs)and intercellular CO2 concentration(Ci)were significantly different.And the photosynthetic rate of near situ conservation experimental site was higher than that on ex-situ conservation experimental site.(3)The net photosynthetic rate were showed positive correlation with transpiration rate,stomatal conductance,water use efficiency and light intensity(PAR),by comparing the photosynthetic rate and its correlation with environmental factors.while the correlation with atmospheric relative humidity(RH)were not obvious.The average daily water use efficiencyon near situ conservation experimental site were ranked as Ammopiptanthus mongolicus>Zygophyllum xanthoxylon>Tetraena mongolica.The average daily water use efficiency of ex situ conservation experimental site were ranked as Zygophyllum xanthoxylon>Ammopiptanthus mongolicus>Tetraena mongolica.The comparison results show that:The tolerance ranges(ecological ranges)of the three relic plants to environmental factors were significantly different in different experimental site.And water factor was identified as one of the important factors limiting the growth of the three relic plants.The growth adaptability and photosynthesis indexes of relic plants in near situ conservation experimental site were found to be much better than those in ex situ conservation experimental site.