| Low temperature stress is a main constraint of rape and corn production, also is one of the common abiotic stress during production process. Seed priming has been shown to improve seed vigor and resistance to adverse conditions. In present study, the effects of seed priming with water, CaCl2, salicylic acid, rare earth,5-aminolevulinic acid, epihomobrassinolide and plant extracts on seed germination and seedling growth were investigated using two rape varieties of’Zheda 619’and’Zheyou 50’. In addition, the effects of three priming methods (hydropriming, sand priming and KNO3+KH2PO4 solution priming) on the germination and seedling growth of normal corn ("Nongda 108’), waxy corn ("Meiyu 3’) and sweet corn (’Xiangtian 1’) under lowtemperature stress were studied. Main results were as follows:All priming methods improved germination energy, germination percentage, germination index, vigor index, root length and root-top ratio, and significantly reduced mean germination time. Except’Zheyou 50’primed with 5-aminolevulinic acid had no difference with the control, other priming all decreased the shoot length as compared with the control. Most priming methods increased the root dry weight of two rape varieties except ’Zheda 619’primed by plant extracts and’Zheyou 50’primed by water. In addition, all priming methods decreased shoot dry weight of two rape varieties. Except CaCl2-priming, all others significantly decreased the relative conductivity of two rape varieties, It suggests that water, CaCl2, salicylic acid, rare earth,5-aminolevulinic acid, epihomobrassinolide and plant extracts can be used as priming solutions to improve seed vigor of rape.Seed germination and seedling growth were measured under 8℃ low temperature stress, all seven priming methods increased the germination energy, germination percentage, germination index and vigor index, shortened mean germination time of’Zheda 619’and ’Zheyou 50’, and increased root-top ratio and root dry weight, decreaced shoot dry weight of two rape varieties. Seedling physiological charactristics were tested before and after low temperature treatment (5℃) and recovery growth for three days (20℃), seven priming methods imprived proline content and APX activity of two rape varieties before low temperature, and improved chlorophyll content and POD, CAT activity of’Zheyou 50’. After 5℃ low temperature treatment, all priming methods increased CAT activity, chlorophyll and proline content of’Zheda 619’, and increased POD, APX activity and chlorophyll content of heyou 50’. After recovering growth, seven priming methods increased POD, CAT activity of two rape varieties, and increased APX activity and proline content of’Zheyou 50’. Thus, it seems that priming by water, CaCl2, salicylic acid, rare earth,5-aminolevulinic acid, epihomobrassinolide and plant extracts can promote seed germination and seedling growth of’Zheda 619’and’Zheyou 50’under low temperature, thereby improve their chilling-tolerance.The activity change of isocitratelyase in’Zheyou 50’during priming and germination under 8℃ low temperature was measured. During priming, hydropriming, salicylic acid priming, rare earth priming,5-aminolevulinic acid priming, epihomobrassinolide priming and plantextracts priming improved the activity of isocitratelyase, while after dehydration, hydropriming, epihomobrassinolide priming and plantextracts priming decreased the activity of isocitratelyase. During seed germination, the activity of isocitratelyase gradually increased, and slightly decreased after the fifth day of germination, the activity of isocitratelyase treated by seven priming methods was all higher than that of the control. It suggests that the priming improved the actitity of isocitratelyase in rape seed and seedling.The effects of hydropriming, sand priming and KNO3+KH2PO4 solution priming on seed germination and seedling growth of corn were investigated before and after low temperature treatment (at 5℃ for three days) and recovery growth for three days (at 25℃). Three priming methods had no significant effects on germination percentage of normal corn, waxy corn and sweet corn, however, they could significantly improve germination energy, germination index, shoot length and shoot dry and fresh weights, and short mean germination time in normal corn, waxy corn and sweet corn. The relative conductivity of three types of corn was decreased by hydropriming and sand priming, was significantly declined by solution priming in sweet corn. The three priming methods increased chlorophyll content of normal corn in three stages, sweet corn before lowtemperature stress and after recovering growth and waxy corn after recovering growth. Before and after lowtemperature stress, hydropriming enhanced the POD activity of three types of corn. After lowtemperature stress for three days, sand priming promoted the CAT activity of three types of corn. After recovering growth, sand priming raised the activities of POD, CAT and APX in three types of corn, and solution priming increased APX activity of three types of corn. Three priming methods significantly reduced the MDA content of waxy corn and sweet corn after lowtemperature stress. It suggests that three priming methods could increase seed vigor and improve the chilling tolerance of normal, waxy and sweet corn. Sand priming had advantage in improving seed vigor of waxy corn, hydropriming showed better improvement for sweet corn. However, there was no significant difference among the three priming methods for normal corn. |
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