Studies On The Difference Of Response To Cadmium Stress In Rice Seed Germination And Seedling Stage

In order to study the effects of cadmium stress on seed germination and seedling growth of rice,and the differences in physiology and biochemistry indexes of cadmium stress resistant rice varieties under cadmium stress,water culture method was used in the germination test of 102 rice cultivars?lines?with 0?distilled water control?,0.5,1.0,2.0mmol/LCdCl₂·2.5H₂O as the concentration of cadmium treatment solution.Their germination characteristics such as germination potential,germination rate,germination index,vitality index,length of embryo,radicle length,embryo fresh weight and dry weight were measured.According to the differences in resistance to cadmium stress at the germination stage of the tested rice cultivars?lines?,six rice cultivars?lines?were selected of Huang Huazhan and 28 zhan?Cd stress tolerance type?,Huang Yuezhan and Feng Huazhan?medium resistance to cadmium stress?,Huang Yuezhan and Ai Xiu Zhan?cadmium stress sensitive?.Their shoot height,root length,fresh weight and dry weight,cell membrane permeability,malondialdehyde and proline content,SOD?superoxide dismutase?and POD?peroxidase?,CAT?catalase?activity,chlorophyll content and chlorophyll fluorescence parameters at the seedling stage were measured.And the following results have been obtained:1.The average germination rate,germination potential,germination index,vigor index,germ length,radicle length and fresh weight of 102 rice cultivars both decreased with the increase of cadmium stress concentration.And the different rice cultivars?lines?among difference in cadmium stress concentration reached a significant or extremely significant level.According to the difference of cadmium stress in seed germination period of different rice cultivars,102 rice cultivars were divided into three types:Huang Huazhan,XiangWanXian6,XiWangR141 and other 18 rice cultivars?lines?for cadmium-resistant rice cultivars?lines?,FuXuan201xuan,MingHui63,FuXian201Xuan 48 rice cultivars?lines?for the medium resistance to cadmium rice cultivars?lines?,There are 36 rice cultivars?lines?of cadmium sensitive rice cultivars?lines?,including Huixuanyouxiaoli1,Qizhandao,Jin23B.2.Seedling height,root length,fresh weight and dry weight of the seedlings of the cadmium-stress sensitive rice cultivar?lines?Ai xiuzhan was significantly reduced under low concentrations of 0.05 and 0.1mmol/LCd²⁺not significant difference in seedling height,root length,fresh weight,and dry weight of other five rice cultivars?lines?compared with the controlThe seedling height,root length,fresh weight and dry weight of all rice cultivars treated with 0.20 mmol/L Cd²⁺and Cd²⁺at high concentrations were significantly lower than those of the control,and the seedlings of the rice cultivars Huang Yuezhan and Ai xiu Zhan.Growth indexes such as height,root length,fresh weight,and dry weight were greater than those of other four rice cultivars.It indicated that the high concentration treatment of cadmium stress had a significant inhibitory effect on the growth of all six rice cultivars?lines?.Among them,the growth inhibition of cadmium-stress sensitive rice cultivars Huang Yuezhan and Ai Xiu zhan was greater than others.3.The leaf membrane permeability,MDA content,proline content,SOD,POD and CAT activity of the rice cultivars?lines?were increased with the increase of cadmium stress of Huang Huazhan and 28 Zhan,Huang Yue Zhan Xuan and Feng Huazhan,Huang Yuezhan and Ai Xiu Zhan.the chlorophyll content decreased of seedlings of the tested rice cultivars?lines?under cadmium stress,the initial fluorescence?F₀?of photosynthesis PSII increased,the maximum photochemical efficiency?Fv/Fm?decreased,and the actual quantum efficiency of photochemical conversion??PSII?decreased,the non-photochemical quenching coefficient?qN?decreased,the photochemical quenching coefficient?qP?increased,and the apparent electron transfer efficiency?ETR?decreased.4.Comprehensive analysis results showed that Cd stress-tolerant rice cultivars Huang Huazhan and 28 accounted for a strong resistance to cadmium stress,and their growth and physiological biochemical indicators were relatively stable under cadmium stress.Cadmium stress-sensitive rice cultivars showed weaker resistance to cadmium stress and their growth.Physiological and biochemical indicators were significantly inhibited under cadmium stress.While the growth and physiology and biochemistry of moderate-resistance rice cultivars?lines?Huang Yuezhan and Fenghuazhan under cadmium stress were among the cadmium stress tolerant rice cultivars and cadmium stress-sensitive rice cultivars.