| In the subtropical areas, Imperata koenigii, a kind of vicious weed, often invaded into the lawn, which directly affected lawn landscape, or even completely replaced turfgrass. For the problem, a substituted experiment was designed, and five gradients of I. koenigii were artificially invaded into Zoysia tenuifolia turf. After trimming and drought treating, some indexes relevant with morphological and physiological active substances were measured. The effect of intrusion amount of I. koenigii on competitiveness and growth potential of Z.tenuifolia was analyzed. The purpose of study was to explore the effective method to controlling weed, and to provide theoretical basis for planting and maintaining lawn. Main research results were as follows:(1)By replacing experimental design, the interspecific competition between I. koenigii and Z. tenuifolia were studied from plant morphology, biomass,attack power and interspecific competition, etc. The results show: Invasion amount of I. koenigii all had a highly significant effect on seedling leaf length,leaf thickness, leaf number, total leaf area, plant height, tiller of Z. tenuifolia(P<0.01). A decreasing trend was found with invasion amount of I. koenigii increasing, and the greater intrusion amount, the more difference was found(P<0.05). But the amount had no significant effect on leaf width(P>0.05).Influence order of I. koenigii on leaf traits of Z. tenuifolia was leaf length> leaf number > total leaf area > leaf thickness > leaf width. Intrusion amount of I.koenigii had no significant effect on relative yields of Z. tenuifolia shoot(P>0.05), but significant effects on underground relative yield(RS)(P<0.01).The competitive relationship between two species was changed with the intrusion amounmt increasing. The aboveground part of Z. tenuifolia transformed intraspecific competition to interspecific competition, yet the underground part was the opposite, from interspecific competition to intraspecific competition. Intrusion amount of I. koenigii had significant effect on total intrusion community relative yield total of aboveground community(S)had significant effect(P<0.05), but no significant effect on total relative yield the of undergroundwater in the community of relative yield total(R) without significant effect(P>0.05). That’s to say stem and leaf of the two species of stem and leaf haveexisted antagonism, and the competition between the two species is mainly manifested were competition of in the stems and leaves of the competition; Intrusion amount of I. koenigii Imperata intrusion have had very highly significant effect on t attack index of o Imperata underground and abovegroundstrike force index I. koenigii(P<0.01). When intrusion amount of I.koenigii was 10%, the attack force was the strongest attack. With intrusion amount of I. koenigii increasing, attack force index sharply fell, which showed intraspecific competition. There was no significant effect on the competitive balance index(P>0.05), which indicated that competitive ability of Z. tenuifolia was less than that of I. koenigii.(2) Trimming test: By 3 times trimming with the stubble height of 7cm,morphological index and biomass, etc. were determined, and turf quality was evaluated by using nine-point standard. The results showed that: Under the condition of same intrusion amount of invasion, pruning times had significant effects on leaf length of Z. tenuifolia, but no significant effect on its leaf width and leaf thickness. Leaf length increased with mowing trimming frequency increasing, but leaf width was opposite. When trimmed 2 times, Z. tenuifolia got maximal leaf length and minimal width. The pruning times had no significant effect on leaf thickness of Z. tenuifolia. Leaf thickness was a trend of dropping to rising with the mowing frequency increasing, and got minimum under the condition of one time trimming. Pruning times had different effects on plant height and tiller of Z. tenuifolia. These two index generally was an upward trend with pruning times increasing. Mowing frequency and intrusion amount of I.koenigii significantly affected fresh and dry weight of Z. tenuifolia(P< 0.01).Intrusion volume had a larger effect on the fresh weight, but pruning had a larger effect on dry weight. At the same mowing frequency, leaf length, leaf width, leaf thickness, plant height and tiller of Zoysia existed difference becauseof different I. koenigii amount. Invasion amount of I. koenigii had no obvoius effect on texture(P> 0.05), but a significant effect on other quality indexes and comprehensive score(P<0.01). Pruning had a significant effect on density and color of Z. tenuifolia(P<0.05), and a highly significant effect on texture(P<0.01). But pruning had no obvious effect on the uniformity and comprehensive scores(P<0.01). Pruning had a significant effect score(P>0.05).(3)Drought stress test: After Z. tenuifolia turf invaded by I. koenigii continuously dried 0, 5, 10, 15 d, respectively, the physiological changes of Z.tenuifolia and its mechanism to stress was analyzed and explored.Results showed that: Drought stress and invasion amount both had significant effect on SOD, POD, SS, SP, PRO, MDA(P<0.01), and a highly significant interaction was found between drought stress and invasion amount(P<0.01). Drought stress had significant effect on CAT(P<0.05), and a highly significantly effect on CAT(P<0.01), and there was also a highly significant interaction between drought stress and intrusion amount(P<0.01). Drought stress significantly reduced the resistance of Zoysia, so that it was difficult to improve the competition ability by increasing content of SOD when invaded by many I.koenigii. Zoysia can improve resistance by increasing content of POD under the condition of mild and moderate water stress, and also increased POD content under the condition of severe drought adding to smaller invasion amount of Imperata. But Zoysia can not increase POD content under the condition of severe drought adding to many weeds. Zoysia can increase CAT content for enhancing its resistance and competitiveness under the condition of severe water stress and higher amount of weed. Under the condition of severe drought, Z.tenuifolia can increase SS content for ensuring penetration of cells with the invasion amount increasoffing, which can reduce the damage of adverse environment to plant. Zoysia in the adverse conditions also can increase SP content to ensure their own growth. But the stress was a certain limit, Z.tenuifolia can not regulated themselves through SP content. Zoysia in the condition of moderate drought can enhance their competitiveness by increasingPRO content but PRO content significantly decreased under the condition of severe drought, Z. tenuifolia can not adjust intracellular osmotic pressure.Drought stress and intrusion amount of I. koenigii both had great influence on MDA content, and significantly damaged plant cell membrane. But impact of drought stress on MDA content was far greater than that of invasive amoun.In summary, I. koenigii intrusion mainly inhibited tillering ability and shoot biomass accumulation of Z. tenuifolia, but promoted the development of roots of Z. tenuifolia. Pruning had advantages to leaf length, plant height and tiller of Z. tenuifolia, but the role to improving the competitiveness of Zoysia was limited. Under the drought stress, Zoysia can improve its resistance by regulating the antioxidant enzymes and osmotic adjustment substances in the body. Because warm-season grasses had certain requirements to temperature,together with short green period, long yellow period, lower daily maintenance and unreasonable technology, etc., there existed the risk of I. koenigii invasion at any time. So, to carry out series of study to I. koenigii, such as propagation characteristics, invasion pathways and damage regularity to warm-season turf,was necessary requirement of controlling weed, improving turf quality and prolonging the life of lawn. |
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