In response surface analysis (RSA), a surface of predicted, usually second-order response over a range of quantitative and continuous factor levels is estimated. Less information is available on how to apply RSA in the case of multiple response values that do not show similar trends. This paper provides a solution for this situation by applying first a principal component analysis (PCA) and then taking the first principal component in the RSA. This method is applied to select the optimal seed treatment for breaking dormancy in spinach (Spinacia oleracea L.). Fourteen treatment combinations of the two factors gibberellin (GA3) concentration and soaking period, each with five levels were selected and germination percentage, energy of germination and germination index were determined. The three response values were analyzed by PCA and the first principal component was analyzed by RSA. The obtained optimal treatment combination, GA3 at 261mg/L and a soaking time of 22.1h, was able to increase the germination percentage from 56% to 91.3% and the energy of germination from 38% to 68.7%, respectively. The optimal conditions obtained from the individual response values were different from this optimum.

Seed germination and seedling development at different Pb concentrations in three rice varieties (Jiayu 293, Jiayu 948 and Xieyou 963) were investigted. The method of qualitative trait combining with quantitative trait by orthogonal polynomials was applied to analyze rice seed vigour by regression model. Seeds from different rice varieties showed different sensitivities to Pb poison, in the Pb concentration of 100--700mg/L, Pb had significant inhibitory effects on root length and shoot height, and the restraint would aggravate along with the increase of Pb concentration. However, Pb had no inhibitory effect on root dry weight and shoot dry weight, indicating that different physiological characteristics had different sensitive re-actions to Pb. The gained predicting equation of regression could predict the effects on rice seed vigour at different Pb concen-trations.

Two seed lots of lettuce (Lactuca sativa L.) cv. Kr61owa Majowych were primed in polyethylene glycol (PEG) 8000 at-1.25MPa for 7 days in dark at 20℃. Two fungicide treatments combined with PEG were used to control fungi: 1) Funaben T (0.1%) and Apron 35 SD (0.02%) were added to -1.25MPa PEG solution (PEG+F); 2) After seed priming and drying, Funaben T was mixed at 5g kg 1 and Apron 35 SD at 1g kg-1 of seeds (PEG then F dust). PEG, PEG+F and PEG then F dust treatments reduced significantly thermodormancy and increased the seed germination at 35℃ in both lots. PEG then F dust treatment had the best effect on reducing seed thermodormancy at 35℃, and increased seed germination to 64.5% in lot 1 and 72.0% in lot 2 compared to 0 in untreated. PEG and PEG then F dust treatments have accelerated germination speed at 20 and 15℃ in both lots. There was a significant reduction in seed infestation in which the seeds were treated with PEG+F and PEG then F dust compared to untreated seeds and PEG primed seeds. PEG priming enhanced seed infestation considerably by Alternaria alternata, Penicillium spp., Rhizopus spp. and Ulocladium spp. Mycological analysis showed higher frequency of Alternaria alternata and Ulocladium spp. in untreated seeds at 20℃. Priming in combination with fungicides significantly alleviated the infestation of fungi, especially Alternaria alternata infestation.

A priming method called sand priming was developed using sand as a priming solid matrix in present experiment. Seeds were mixed with sands that contained 3.8% (v/w) water and sealed in plastic box and then were primed at 18℃ for 72h. Four varieties of rice were used to investigate the effect of sand priming on germination of direct-sown rice (Oryza sativa L.) in the laboratory. The results showed that the energy of germination, germination percentage, germination index and vigor index were improved in four varieties. Meanwhile, seedling height, root length, number of root and root dry weight were significantly higher than the nonprimed controls. Field experiments showed that the seed establishment and yield in sand primed seeds were significantly increased by 19.8%-22.9% and by 9.8%-31.2%, respectively as compared to soaked seeds without priming. It is indicated that sand priming method may help to improve seedling establishment in direct-sown rice and possible to be used in the field croo oroduction.