| Hemp is an is an annual herb belonging to the family of Cannabinaceae, the genus of Cannabis, the species of Cannabis Sativa L. Requirements of hemp cultivation on climate and soil is not harsh, and it has the ecological adaptability and the effect of environmental protection. If we can use heavy metal contaminated soil to grow hemp,it has a positive effect on reducing the cost of textile products and enhancing environmental remediation.Based on the excellent properties of hemp and documents about Effects of Zn/Cd stress on plant.Effects of Zn/Cd stress on growth, photosynthesis and fiber properties in Yunnan hemp-1 were studied bywater culture.The results were concluded as follow:(1) Hemp seedling roots are more sensitive to zinc and cadmium treatment, germination rate and stem length of hemp are insensitive to low concentrations of zinc or cadmium. With the increase of the concentrations of zinc and cadmium, all of them in the root content> leaf content, it through enrichingconcentration of the root to reduce damage to overground parts.(2) For a long time of zinc and cadmium stress would seriously reduce the hemp net photosynthetic rate, transpiration rate, stomatal conductance, but will increase the intercellular CO2 concentration, photosynthetic rate of decline were caused by non stomatal factors under the stress of cadmium and zinc.(3)Zinc deficiency and high zinc stress could significantly decrease the content of chlorophyll a, chlorophyll b and carotenoid content. The reduction of the Chi a/B ratio can avoid light damage which may be aself-protection Mechanis to againstzinc stress.With the increase of cadmium concentration, Chlorophyll a, chlorophyll b and carotenoid concentrations of hempleavesdecreased, and the decreased speed was carotenoid> chlorophyll b and chlorophyll a.Sacrifice of carotenoids could been used to protect chlorophyll and defensecadmiumstress.(4)During the zinc and cadmiumstress process, maximal photochemcial efficiency of PS II (Fv/Fm),The actual quantum yield (Yield),the photochemical quenching coefficient (qP) andthe photosynthetic electron transport rate (ETR) decreased.Cadmium had a stronger inhibitory effect on Fv/Fm than zinc. Hemp rapidly produced excess luminous energywith zinc and cadmium stress in relatively short time, by increasing the amount of antenna dissipative, and reducing the amount of light reaction to ease excessluminous energy damage to the photosynthetic apparatus. With the increase of cd stress level, the PS Ⅱ reaction center capture excess excitation energy efficiency decreases, and excess energy could increase the imbalance between the two optical systems, the multi excitation energy distribution to PS Ⅱ, and drops hemp leaves the actual photochemical efficiency of photosystem Ⅱ (yield), PS Ⅱ accumulated more excitation energy, the degree of openness reduced and eventually led to optical system of photoinhibition. Non photochemical fluorescence quenching protection mechanism play a significant effectunder stress of cadmium and zinc, which may have some association with the heavy metal tolerance of hemp.(5)With cadmium and zinc concentrations increased, the lignin content of hemp fiber in the fat and wax content and lignin showed rising trend, water soluble, pectin and hemicellulose content had no significant effect, but fiber cellulose content was decreased. Effects on the fibrous type index werenot obvious with different concentrations of zinc stress, crystal index of hemp fibers treated by cadmium decreased slightly. No obvious effects of concentration of zinc and cadmium stress on the physical structure of hemp fiber, bast fiber void size changes little. Antibacterial fiber extract on Staphylococcus aureus and Pseudomonas aeruginosa were significantly enhanced compared with the control, antibacterial resistance under Cadmium Stress was stronger thanits under zinc stress. |
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