| During growth period, boric acid and sodium silicate were injected into the trunk of Populus to achieve some antiseptic ability under ambient temperature and pressure,which based on the technique of trunk injection.Some related theories were also expounded and analyzed in this paper,detail as follows: preliminary experiment on the objectivity rule of sap flow were studied to confirm the initial drug injection time,leaching of boric acid with different drug formulas were explored, drug loading dosage was tested in different height of the trunk, then the anticorrosion performance against decay fungi between untreated poplars and treated ones was compared. The results of this study are summarized below.(1)The sap flow velocity of Populus is influenced by meteorological factors,it presents a narrower bimodal curve in the sunny days during the day time, while cloudy day is not obvious. In addition, for different diameter of Populus, sap flow velocity of the bigger diameter higher than that of the smaller one during 6:30 to 16:00, but the bigger in diameter, the utilization ratio of weak light will be lower.(2)The objectivity rule of sap flow velocity is low and unstable,but not totally zero at night, it drops to near zero at about 19:00 after sunset, so the initial drug injection time will be 19:00 in theory. However, due to the limitation of experimental conditions, we started the experiment at about 18:30.(3)The Populus has a threshold to the boron content, one-time continuous input of boric acid can cause excessive boron poisoning even to death. So in this experiment, 1000 ml 1.5% boric acid was injected in the second set of samples with the lowest speed, then 3000 ml 0.5% sodium silicate was injected, finally, 1000 ml 1.5% boric acid was input once again.(4) The Populus was cut down immediately after the injection to prepare samples for further experiments. After leaching in water, the weightlessness rate of samples showed that: 1-a(samples only injected boric acid) >2-a(samples injected boric acid and sodium silicate) > 3-a(samples only injected sodium silicate)>4-a(control group which injected distilled water);in addition,1-a is slightly greater than 2- a, the weightlessness rate of 3-a is greater than 4-a by only 0.09%;so we know that sodium silicate only partially prevent the boric acid from leaching in water, and sodium silicate itself almost does not loss at all.(5) The drug loading dosage shows that: boric acid has been transported to the tree top of Populus,while sodium silicate has not reached the treetop even perhaps not arrived at 2 meter higher than the injection hole location; drug loading dosage at different height of the trunk is uneven, loading dosage has a highly negative correlation with the height of sample, and 30 cm distance of the injection hole is significantly higher than the other test position.(6) On the cross section, block shaped deposit can be seen in vessels and fibers of the sample 2-a which injected both boric acid and sodium silicate, and tiny particles attached to the surface of cell wall.On the tangential and radial section, deposit can be seen in vessels ?rays?inter-vessel pits and vessel-ray pitting. Two kinds of deposit was found in cells, the larger clumps are mainly distributed in the vessels, while the smaller particles can be seen in vessels ?rays ?inter-vessel pits and vessel-ray pitting.(7) The test of natural durability corrosion in the laboratory showed that the average mass loss rate of different samples at the same height of the trunk is as follows: for the samples 30 cm over the injection hole, 2-a<1-a<4-a, and their decay resistance level is resistance?slight-resistance and nonresistance in sequence; for the samples 2 m over the injection hole, 2-b<1-b<4-b, their decay resistance level is slight-resistance?slight-resistance and nonresistance; decay resistance level for the samples 4 m over the injection hole is all nonresistance. Thus infer that sodium silicate can improve the corrosion performance of boric acid, to a certain extent, and mass loss rate at the same height of trunk is: 2 < 1 <4.(8) The test of natural durability corrosion in the laboratory showed that the average mass loss rate of the same samples at different height of the trunk is as follows: for samples injected boric acid, 1-a < 1-b < 1-c, their decay resistance level is slight-resistance ? slight-resistance and nonresistance in sequence; for samples injected boric acid and sodium silicate, 2-a<2-b<2-c, their decay resistance level is resistance?slight-resistance and nonresistance. Thus we known mass loss rate is closely relative to the distance from injection hole, the closer distance the weightlessness rate is lower, the stronger ability to resist infection of white-rot fungus, the better antiseptic effect. |
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