Studies On Photosynthetic Properties Of Apricot (Prunus Armeniaca L.) And Nectarine(Prunus Persica Var. Nectarina Maxim) To Greenhouse And Field Grown Conditions

In this study, three cultivars of apricot and nectarine wre evaluated under open-field and solar-heated greenhouse conditions to determine the effect of photosynthetic photon flux density, leaf temperature, and CO₂ concentration on phtosynthetic rate, apparent quantum yield, and carboxylation efficiecy, maximum quantum efficiency of PS II photochemistry, etc.The results obtained here were summarized as follows:1. Three apricot cultivars Katy, Erhuacao and Sungold, have the similar ability to use light and CO₂ in open-field condition. The net photosynthetic rate at light saturation point(Amax) of Katy in greenhouse was 22.37μmol m^-2 s^-1, which was 35% and 38.8% higher than Sungold (16.55μmol m^-2 s^-1) and Erhuacao (16.12μmol m^-2 s^-1), and also, Katy had the higher ability to use CO₂ in greenhouse. In open-field, the favorable temperature for photosynthesis of European-American cultivars was 5℃higher than Chinese cultivar Erhuacao, however, when they grown in greenhouse, this was decreasing from 35℃to 30℃and 22℃for Sungold and Katy, respectively, while, Erhuacao kept the same with open-field, 30℃. Furthermore, the Pn under the favorable temperature increased from 16.5μmol m^-2 s^-1 to 20.9μmol m^-2 s^-1 for Katy, and 16.2μmol m^-2 s^-1 to 19.5μmol m^-2 s^-1 for Sungold when they grown in greenhouse, but, Erhuacao did not change.2. In open-field condition, the daily average Pn was Katy (11.74μmol m^-2 s^-1) >Sungold(10.05μmol m^-2 s^-1)>Erhuacao(7.63μmol m^-2 s^-1), while in greenhouse, it was Katy (8.25μmol m^-2 s^-1)>Erhuacao (6.6μmol m^-2 s^-1)>Sungold (6.28μmol m^-2 s^-1)。Double peaks curve of Diurnal variations of net photosynthetic rate (Pn) were observed in open-field for all three cultivars of apricot and also the others parameters, such as the diurnal variations of minimal or initial fluorescence intensity (Fo) , maximal fluorescence intensity (Fm) and maximum quantum efficiency of PS II photochemistry (Fv/Fm) . The lowest value of Fv/Fm was measured at 12:00, it was accordant with photosynthesis.3.Yanguang had the highest efficiency to use light than Huaguang and Zaohongzhu in open-field, however, Huaguang could improve Amax from 18.6μmol m^-2 s^-1 to 21.5μmol m^-2 s^-1 when it grown in greenhouse, on the contrary, Amax of Yanguang decreased from 20.47μmol m^-2 s^-1 to 18.7μmol m^-2 s^-1, it seemed that Huaguang adapt the greenhouse condition better than the other two nectarine cultivars.There were no significant difference between the two grown conditions and among three cultivars for the RuBPmax (maximum regeneration rate of RuBP),even there were a little increasing in greenhouse. In greenhouse, the Pn-T curve showed that 25—30℃produce the highest Pn, meantime, the C_i (intercellular CO₂ concentration) had the lowest value. Stomatal conductance was sensitive to Temperature, below 20℃, Stomatal conductance increased slightly to 2000μmol m^-2 s^-1 with the increasing of temperature, and then decreased rapidly to <500μmol m^-2 s^-1 with the increasing of temperature.4.The daily average Pn of Zaohongzhu and Huaguang increased from 8.25μmol m^-2 s^-1 to 9.97μmol m^-2 s^-1, and from 8.37μmol m^-2 s^-1 to 8.43μmol m^-2 s^-1, respectively, on the contrary, decreased from 8.09μmol m^-2 s^-1 to 7.40μmol m^-2 s^-1 was obtained for Yanguang。The Diurnal variations of net photosynthetic rate and efficiency of PSII of three cultivars of nectarine were decreased seriously at 15:00, Fv/Fm decreased from 0.8 to 0.65, Yanguang had the maximal decline, 0.55。Double peaks of Diurnal variations of net photosynthetic rate (Pn)curve were observed for the three cultivars. While in greenhouse, Fv/Fm was varied between 0.85-0.75, and the one peak curve of diurnal variations of net photosynthetic rate was measured. The NPQ and ETR values had a higher decline in the med-day when grown in open-field, compared to in greenhouse, furthermore, Zaohongzhu marked the maximal decline. 5. Chlorophyll (chl) a content were declined in greenhouse in the three cultivars. A reduction in chlorophyll (chl) a/b ratio in leaves of greenhouse grown plants with significant increase in chlorophyll (chl) b content were obtained. The results suggest that some nectarine cultivars have the ability to acclimate to the solar-heated greenhouse growth condition.6. The result of this study supports that, depend on the different genotype background, different cultivars of apricot and nectarine shown different ability to adapt to the greenhouse grown condition. The photosynthetic characteristic were correspondence with the production ability. But, just depend on the result of the photosynthetic ability in open-field grown condition, it is difficult to select the cultivar which fit for the greenhouse production. However, the parameters obtained in greenhouse could be a good tool for the selection. Chlorophyll fluorescence is a useful tool to analyse the station of photosystem II as a assistant method.