| Allelopathy,which has the important influence on forestry and natural ecological system,is widely exist in nature,and it plays important roles in crop autotoxicity,failed forest regeneration,plant invasion and so on.Allelochemicals are widely exist in plants of various tissues and organs and rhizosphere soil,they get into the environment by four main pathways:root secretion,leaching,volatilization,and plant residues decomposition.In South China,especially in plain and foothill region of Sichuan Province,because of the exuberant branches and leaves,beautiful tree appearance and strong adaptability,C.Septentrionale has been widely introduced and planted as rural four sides gardening trees and included in some traditional agroforestry system(garden-style agroforestry and planting trees in the farmland).However,the research shows that Cinnamomum Septentrionale has strong allelopathic effects,and its leaf litter may have adverse effect on the growth of crops.Therefore,pot-culture experiment was conducted to study the effects of decomposing C.Septentrionale leaf litter on the growth,physiology of Zea may and explore the ameliorating effects of base fertilizer and topdressing.In addition,the research results can provide theoretical basis and technical reference for the collocation of species(C.Septentrionale and crops)and leaf litter management.Results were shown as follows:(1)Effects of C.septentrionale leaf litter on the growth,biomass and yield of Z.maysOwing to the decomposition of C.Septentrionale leaf litter,the growth of Z.mays was inhibited in varying degrees,as shown in height,base diameter,fresh weight,leaf area,grain yield and so on.With the increase amount of leaf litter,the inhibition of allelopathy increased.After 60 days of decomposition,the height and base diameter were significantly inhibited by T2 and T3 treatments.The inhibition on leaf area became stronger with the increase amount of leaf litter,and the average RI were-0.283?-0.427 and-0.759 respectively.During the first 10 days' decomposition,the decomposition of C.Septentrionale leaf litter showed no obvious impact on the biomass of Z.mays,but with the decomposition prolonged,the inhibitory effect of leaf litter gradually strengthened.With the increase amount of leaf-litter,grains per panicle and yield decreased declined significantly,and the RI were-0.275?-0.409?-0.525 and-0.232?-0.312?-0.454 respectively.The thousand kernel weight(TKW)of Z.mays showed a downward trend,but no obvious differences were observed among all treatments.(2)The response of Z.mays resistance physiology to C.septentrionale leaf litter decomposition20 days after sowing,the activity of CAT(catalase),SOD(superoxide dismutase),POD(peroxidase)and the SP(soluble protein)content showed no significant differences among all treatments,but the content of MDA(malondialdehyde)was significantly increased.After 20 days of decomposition,the content of SS(soluble sugar)was significantly increased in all treatments but the SP(soluble protein)content was significantly inhibited in T3 treatment.After 40 days of decomposition,the activity of CAT,SOD,POD was significantly inhibited,but the content of MDA showed no significant differences among all treatments;Meanwhile,the content of SS showed no significant differences among all treatments while the content of SP was significantly inhibited.With the decomposition time prolonged,most indexes showed no significant differences.(3)Effects of C.septentrionale leaf litter on the photosynthetic physiology of Z.maysThe addition of leaf litter decreased photosynthetic pigments contents of Z.mays,furthermore,when the amount of C.septentrionale leaf litter reached a certain level,the ratio of Chla/b increased while the ratio of Chl/Car decreased significantly.The Pn(photosynthetic rate)was dramatically declined at T3 treatment,in addition,T2 and T3 treatments notably inhibited the LCP(light compensation point)and LSP(light saturation point),indicating that,in terms of low and high light levels,the adaptability of Z.mays was dramatically inhibited by T2 and T3 treatments.With the increase amount of leaf litter,the(CCP)CO2 compensation point declined while the(CSP)CO2 saturation point increased significantly,illustrating that the addition of leaf litter significantly inhibited the CO2 absorption of Z.mays;The Rp(photorespiration rate)increased with the increase amount of leaf litter,which was advantageous to the excess light energy dissipation and could protect the photosynthetic mechanism from the damage of strong light.(4)Effects of C.septentrionale leaf litter on soil enzyme activitiesThe decomposition of C.septentrionale had little effect on soil urease activity,and it was only at T2(after 40 days decomposition)and T3(after 60 days decomposition),the urease activity was notably inhibited.After 20 days decomposition,the addition of leaf litter increased the soil phosphatase and invertase activity,illustrating that the decomposition of leaf litter could provide more nutrients to plants,but it was worth noting that the interaction of enzymes and microorganisms could produce more peroxide in soil,which might injure the roots system of plants,then disturb the nutrients absorption of Z.mays.(5)Ameliorating effects of fertilization on the allelopathy of C.septentrionale leaf litterThe average RI were-1.153 and-0.975,respectively with base fertilizer and topdressing,both were higher than the RI(-3.453)of none-fertilizing test,which illustrated that fertilizing could significantly improve the growth of Z.mays though it could not completely eliminate the inhibition of C septentrionale leaf litter.In conclusion,the decomposition of C septentrionale leaf litter inhibited the growth of Z.mays,with the increase amount of leaf litter,the inhibition of leaf litter increased,whereas,the inhibition increased firstly and then declined with the decomposition prolonged.Fertilizing is an important measure for relieving the allelopathic effects of C.septentrionale leaf litter,and topdressing works better than base fertilizer. |
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