The Physiological Basis For The Difference In Growth Potential Of Hybrid Populus Deltoides

To investigate differences in physiological characteristics of growth and physiologicalbasis of high growth vigor in the first generation of Populus deltoides which are from differentgrowth vigor clones,here we chose two groups of seedlings with different growth vigor:HIGH(A) and LOW (B), for comparison,with the Parents as controls. Indexes of phenotypeand physiology were successively measured to study the growth,photosynthesis and nutrientabsorption,and related research was carried out in the field of growth, photosynthesis andnutrient absorption. The research results in:1,There were significant or very significant differences in dry weight of root, stem,leafand the total between A and B.A3was the maximum value of total dry weight,reached33.25g,and the minimum was B2,only12.82g. The dry matter of root was assigned the minimum indifferent components. The largest proportion was stem in A,the mean was45.15%, while it wasthe leaf in B, and the mean of stem was39.82%in B.2,Changes in growth and physiological characteristics showed a certain regularity duringJune to September.All clones grew most rapidly and physiological characteristics varied mostsignificantly in July;Correlation analysis showed that seedling height and ground diameterwere both significant correlated to leaf area, night respiration rate, NH4+uptake rate and thetotal photosynthetic rate(R>0.826,P<0.05), suggesting that seedling growth was mainlyaffected by their own total photosynthetic capacity, nutrient absorption and night respirationconsumption.3,Diurnal changes of the net photosynthetic rate both showed two-peak curve in the allclones, the first peak all occurred at around10:00, while A carry out efficient photosynthesissignificantly earlier than B and Parents; Analysis of the light response curse showd that Pnmax,AQY, the LCP and the LSP achieved significant differences in addition to Rd. The largest Pnmaxreached21.47μmol. m-2.s-1in A,52.8%higher than B.The LCP of A was the smallest, Only 15.09μmol. m-2.s-1, however, its LSP was Maximum,17.03%and10.35%higher than B andParents respectively.4,Analysis of the CO2response curse showd that there were no significant differences incarboxylation efficiency, CCP and photorespiration rate except Pnmax. The carboxylationefficiency of A was a little higher than B and Parents, but the CCP was a little lower, revealedthat high Growth Vigor clons had a slight advantage in the utilize of CO2. Overall, high GrowthVigor clons had a strong ability to use in low light and carry out relatively efficientphotosynthesis in strong light, But only a slight advantage on the absorption and use of CO2.