Effects Of Exogenous Ca²⁺ On Assimilate Allocation Pattern Of The Poplar Cuttings

Using the methods of morphological index measuring, physiological and biochemical testing, stable isotope analysis techniques, we investigated the dynamic changes of regularity on vegetative growth status of Populus×euramericana'Nanlin 895'cuttings under different concentration of exogenous Ca²⁺ treatment. And that we also explored the effects of exogenous Ca²⁺ on photo-assimilate allocation patterns of Populus×euramericana'Nanlin 895'cuttings. The results showed as follows:1. The exogenous Ca²⁺was able to accelerate the vegetative growth of Populus×Eurameri cana'Nanlin 895'cuttings. The plant height, caliper, bio-yield were superior to control test after spraying different concentration of exogenous Ca²⁺. Thereinto, the 200mg/L Ca²⁺concentration treatment was the best one especially. The 2, 20mg/L Ca²⁺concentrations treatment had a slightly positive effect which was compared with the control test. And the enhance effect would be decreased if the Ca²⁺ concentration reached to 300mg/L.2. The exogenous Ca²⁺could promote the photosynthesis efficiency of Populus×eurameri cana'Nanlin 895'cuttings. With the Ca²⁺ concentration increasing, the Pn,Tr,Gs,Ci of leaves were presented gradually trends of increase in advance, and then decrease without exception. The value of Ci would reach to maximum when the Ca²⁺ concentration treatment was 20mg/L. However, the value of Pn,Tr,Gs would reach to the peak when the concentration exogenous Ca²⁺ concentration treatment was 200mg/L.3. The exogenous Ca²⁺ could increase the chlorophyll and soluble protein content of Populus×euramericana'Nanlin 895'cuttings. And that the relative higher Ca²⁺ concentration presented an obvious stimulative effect. The 200mg/L Ca²⁺ was the optimal concentration before spraying 20 days, while the 100mg/L Ca²⁺ was the optimal concentration after 25 days.4. The exogenous Ca²⁺ could regulate the dynamic changes of soluble sugar content and sugar-metabolizing related-enzyme of Populus×euramericana'Nanlin 895'cuttings. The soluble sugar content and the related enzyme activity of "sink" organ were higher than "source" organ. It was speculated that the exogenous Ca²⁺ could enhance the "sink's" strength, and accelerate the assimilation transportation from "source".5. The stable isotope value of carbon and nitrogen enrichment capacity of Populus×euramericana'Nanlin 895'cuttings were affected by exogenous Ca²⁺. With the Ca²⁺concentration increasing, theδ13C,δ15N value of cuttings were presented gradually trends of increase in advance, and then decrease without exception. The distribution of plants'δ13C,δ15N value should be obeyed the principle that the "sink" organ was bigger than the "source" organ.6. It had a certain accumulative effect that the exogenous Ca²⁺ played a vital role in promoting the growth of Populus×euramericana'Nanlin 895'cuttings. The positive effect of lower Ca²⁺ concentration gradually were enhanced, while the negative effect of higher Ca²⁺ concentration has gradually started to emerge as the extension of growth period.