| Protected cultivation provides an operative way to advance Ziziphus jujuba Mill‘Dongzao’mature season and avoid fruit crack for raining,lead to high economic benefits for jujube cultivation.However,environmental control in facility is a critical for ensuring the progress of growth and production of‘Dongzao’under protected cultivation.The dynamics and ability of photosynthesis could reflect the environmental amenity for plants.In order to explore the photosynthetic characteristics of‘Dongzao’and the associated main constraints under protected cultivation,photosynthetic characteristics under three cultivation models,e.g.,open field,rain shelter and greenhouse,were measured and compared at different phenological phase（budding stage,full booming,fruit early development,fruit expansion,fruit maturity,postharvest）.The results showed that:（1）Environmental conditions in protected cultivation were largely changed compared with those in open field,especially for photosynthetically active radiation（PAR）and vapor pressure deficiency（VPD）.Trees in open field has the highest light intensity and vapor pressure,followed by those in shelter and greenhouse,and diurnal variation displayed similar pattern.the peak of environmental temperature throughout the day was the highest in greenhouse,followed by shelter and open field,there were minor different in the air relative humidity among three cultivation types.Pn is significantly correlated with several factors,such as environmental temperature,PAR,relative humidity and Vpd.In particular,Pn is positively correlated with T and Vpd in greenhouse while negative in open field and shelter.（2）The diurnal change trend of net photosynthetic rate（Pn）under three cultivation models was generally characterized as bimodal curve.Differently,the peak of Pn occurred at afternoon is higher than that at morning in greenhouse.There were no significantly difference in mean Pn and light saturated point among three cultivation models.The stomatal conductance limitation is the main constraint for photosynthesis in the open field,while mesophyll conductance limitation became the main constraint in rain shelter and greenhouse.The diurnal change trend of stomatal conductance（Gs）of jujube plant under three cultivation models were the same as Pn,and the Gs of‘Dongzao’jujube plant in shelter was higher than that in open field before 11:00.However,after 13:00,the Gs in greenhouse is higher than open field.The diurnal change trend of transpiration rate（Tr）of‘Dongzao’plant under open field and greenhouse are characterized as bimodal curve,while that in shelter has three peaks.The Tr of‘Dongzao’plant under three types goes down with Pn between 12:00 and 14:00.The diurnal change trend of water use efficiency（WUE）under three types showed the similar pattern.The mean value of WUE in greenhouse was higher than that in open field and shelter.（3）The relationship between photosynthetically active radiation and photosynthetic parameters of‘Dongzao’are fitted best by the modified rectangular hyperbola model.The light response curves of‘Dongzao’in different growth phase changes in similar way,but the parameters are different.The value of light saturation point varies from 800 to 1200μmol m-2 s-1,while the light compensation point varies from 30 to 50μmol m-2 s-1.In open field,the‘Dongzao’in fruit maturity period has the highest light utilization efficiency,followed by the plant in fruit expansion period,postharvest,budding stage,full booming and fruit early development period.In shelter,‘Dongzao’plant in fruit maturity period has the highest light utilization efficiency,followed by full booming,budding stage,fruit early development,fruit expansion and postharvest period.In greenhouse,the‘Dongzao’plant in fruit maturity period has the highest light utilization efficiency,followed by budding stage,full booming,fruit early development,postharvest and fruit expansion period.（4）The girding decreases the Pn of‘Dongzao’,and aggravates the damage of photoinhibition.The plant using‘Suanzao’（Ziziphus jujuba Mill.var.spinosa）as stocks contributed to a higher light utilization capability than using‘Shuizao’（Ziziphus jujuba cv.‘Shuizao’）as stocks,and alleviate the damage of the midday depression. |
