Comparison Of Seedling Growth Of Four Poplar Clones Under Three Different Acid Soil Types

According to the comparison of growth situation and contents of mineral elements in leaves from P. yunnanensis, P. yunnAnensis xP.triner-vis, P. deltoids Marshand P. ×euramericana 'Neva' under whichthree kinds of acid soils, the adaptability of four poplar species to acid soil were evaluated. By comparison the growth variation and mineral element contents in different parts of the P. deltoids Marsh and P. yunnanensis in different gradient pH culture solution, we studied the acid soil adaptability mechanism of Sichuan native poplar preliminary. The present work provided the basis of cultivation of superior aim at acidic mountain soil conditions in Sichuan and mechanism of adaptability to acid soils from the perspective of molecular biology. The main results were as follows:(1) The P. yunnanensis and P. yunnAnensis×P.triner-vis were endowed with greater adaptability to mountain acidic soil when compared with P. deltoids Marsh and P.×euramericana 'Neva', the most adaptable soil for P. yunnAnensis×P. triner-vis is mountain yellow soil whileP. yunnanensis is most adaptable for red earth and purple soil.(2) The seedling height of P. yunnanensisand P. yunnAnensis×P.triner-vis in three acidic mountain soil were significant higher than P. deltoids Marsh and P. ×euramericana'Neva'. The P. yunnAnensis×P. triner-vis was equipped with highest average increment of 139.26cmin the mountain yellow soil, in contrast, P. deltoids Marsh was minimum with the value of 71.16cmin the same situation. Under the situation of hilly red soil and purple soil, P. yunnanensis was the fastest growing species, with which growth quantity reached 48.64 cm and 53.81 cm, respectively. On the contrary, P.×euramericana'Neva'growed most slowly. The differences of four poplar species growth of ground diameter occured only in the mountain yellow soil under. Sichuan native poplar species diameter growth was significantly higher than that of P.×euramericana species, but their inner differences were not palpable. P. yunnAnensis ×P.triner-vis was processed with the largest increment of 9.66mm while P. deltoids Marsh was provided with minimum value of 7.81mm.The increment in fast-growing period, average growth rate and maximum growth rate of P. ywmanensis and P. yunnAnensis×P.triner-viswerehigher than P.deltoids Marsh and P. ×euramericana'Neva'comprehensively.(3)The contents of mineral elements in functional leaves were significantly different even under the same acid mountain soil for different poplar. Particularly, the total content of mineral elements in the functional leaves of P. yunnanensis and P. yunnAnensis×Ptriner-vis was higher than that of P. yunnanensisand P. yunnAnensis×P.triner-vis. In detail, under yellow soil condition, their absorption ability of copper, zinc and manganese were stronger. With regard to red soil, their absorption ability of copper, iron, manganese and zinc were stronger. For purple soil, they absorbed more nitrogen, magnesium, phosphorus, manganese and zinc. Therefore, it could be speculated that the strong adaptability of native poplar under acid soil maybe due to the strong absorption of mineral elements, especially for the absorption of trace elements.(4)The inhibitory action of above ground growth was decreased with the raise of pH value of culture medium. Under the pH value of 6, the survival rate, seedling height and biomass were optimal for P. yunnanensis, while 7 for P. deltoids Marsh. Furthermore, it can be concluded that the adaptability of P. yunnanensis to acid environment is superior to P. ×euramericana as the fact that larger amount of growth under the same acidity condition.(5) The various roots indexes of P. yunnanensisand P. deltoids Marsh were increased firstly and then decreased with the increment of pH value. Moreover, their roots morphology in the acidic environment are completely different, although the roots of the first order of P. deltoids Marsh was longer than P. yunnanensis in the same treatment, the occurrence and development of the second roots were significantly lower than the contrary. Hence, it is inferred that the roots of P. yunnanensis had played an important role in the adaptability in acidic situation.(6) The value of pH made a difference on the element content of various organs of P.yunnanensis in acidic environment, the order of being affected is:roots> young leaves>functional leaves> old leaves> stem segment. The intake of potassium, calcium, magnesium, copper, iron and manganese decreased significantly with the decrease of pH value. The absorption of copper was affected mainly occurred in pH less than 6, when pH was less than 5.5, the intake of potassium and calcium could be restrained. The inhibition of magnesium, copper, potassium and calcium is mainly through roots absorption, however, the effect of iron and manganese mainly manifested in the transport process of stem segment to leaves.(7) The value of pH took effect on the element content of various organs of P. deltoids Marsh in acidic environment as well, the order of being impacted is:roots> old leaf> functional leaves> stem segment. The intake of calcium, zinc, copper, magnesium, manganese, potassium and phosphorus decreased significantly with the decrease of pH value. The absorption of calcium and magnesium were affected mainly occurred in pH less than 5.5, when pH was less than 5.5, the intake of copper, zinc, manganese, phosphorus and potassium could be restrained. The inhibition of calcium, zinc, copper, magnesium and manganese is mainly through roots absorption, however, the effect of potassium and phosphorus mainly manifested in the transport process of stem segment to leaves.In summary, the adaptabilityofP yunnanensis and P. yunnAnensis×P.triner-vis clones to mountain acid soil were stronger than P.×euramericana. Moreover, the absorption capacities of trace elements werebetter than that of P.×euramericana in the acidic environment. However, the breeding of poplar in China is mainly aimed at the northern planting areas, while the northern cultivation areas are mostly neutral or alkaline soil types, which can not be well adapted to the southern acid soil culture areas. Therefore, this experiments provided a basis for the breeding of poplar in the cultivation area of acid soil in the south of China.