| The frost damage problem of the Trichosanthes kirilowii takes more and more attention of the government and farmers. How to improve the chilling tolerance of Trichosanthes kirilowii has become the urgent problem. Methane Dicarboxylic Aldehyde (MDA) content was taken as the physiological indicator to screen out the good chilling tolerance variety. And enhance the chilling tolerance of Trichosanthes kirilowii in the measure of urea, potassium chloride, salts and salicylic acid. The major results were summarized as follows:1. The less MDA content, the better chilling tolerance was taken as the measurement to to screen out the good chilling tolerance variety. The result was that the MDA content in the leaves of Henan Sanmenxia and Jiangsu Shuyang Trichosanthes kirilowii remained in a relatively low level, and the content changed in a small range. So we thought that the Sanmenxia and Shuyang varieties had good chilling tolerance of Trichosanthes kirilowii.2. At4℃, the MDA content of Trichosanthes kirilowii leaves significantly decreased when sprayed with some concentration of urea. It meant that spraying with urea could play a role of relieving the cold damage to the Trichosanthes kirilowii leaves. And spraying with22.5mmol/L urea had a best effect.At4℃, the MDA content of Trichosanthes kirilowii leaves significantly decreased when sprayed with some concentration of potassium chloride. It meant that spraying with potassium chloride could play a role of relieving the cold damage to the Trichosanthes kirilowii leaves. However, the concentration of potassium chloride was not the key to enhancing the chilling tolerance of Trichosanthes kirilowii.Therefore, a certain concentration of the nitrogen and potash were used into the Trichosanthes kirilowii can significantly enhance the chilling tolerance of Trichosanthes kirilowii. Besides, even if the fertilization exceeded the optimal concentration would not have toxic effect to the Trichosanthes kirilowii. In practical application, using nitrogen and potash into the Trichosanthes kirilowii was a very effective method to improve its chilling tolerance, because it can overcome the damage caused by fertilization excessive.3. At4℃, the chilling tolerance of Trichosanthes kirilowii was enhanced to a certain extent when sprayed with a low concentration of sodium chloride. However, a high concentration of sodium chloride not only could not provide with chilling tolerance, but also hurt the leaves. Spraying with5mmol/L sodium chloride can not only enhance their hardiness, but also in line with the principle of economy.At4℃, the chilling tolerance of Trichosanthes kirilowii was enhanced to a certain extent when sprayed with a low concentration of sodium bicarbonate. The effect was not very good although. However, a high concentration of sodium bicarbonate not only could not provide with chilling tolerance, but also hurt the leaves. Spraying with5mmol/L sodium bicarbonate can not only enhance their hardiness, but also in line with the principle of economy.Therefore, a certain concentration of the sodium chloride and sodium bicarbonate were used into the Trichosanthes kirilowii can enhance the chilling tolerance of Trichosanthes kirilowii in a range. However, if the fertilization exceeded the optimal concentration would have toxic effect to the Trichosanthes kirilowii. Sodium chloride and sodium bicarbonate, to an extent, was an effective method to improve the chilling tolerance of Trichosanthes kirilowii. But in practical applications, this method had significant limitations yet, and how to solve the limitations need further study.4. At4℃, when sprayed salicylic acid to the Trichosanthes kirilowii leaves, the MDA content was obvious controlled. So, spraying salicylic acid played an active and positive role in enhancing the chilling tolerance of Trichosanthes kirilowii. Spraying with1mmol/L salicylic acid can not only enhance their hardiness, but also in line with the principle of economy.5. The induction of MDA in plant leaves under4℃condition was repressed by2.5mg/L ABA treatment, and this repression was more significant in the presence of5.0mg/L ABA. However, further increasing the concentration of ABA did not play more effective role in reducing the MDA content as shown by the abundant value of MDA in7.5mg/L ABA treated plants when compared with that in5.0mg/L ABA treated plants, and this value was even higher in10.0mg/L ABA treated groups. These result suggested the optimal concentration of ABA in blocking the induction of MDA at4℃might be5.0mg/L.The CAT activity did not increase significantly when sprayed with2.5mg/L ABA under4℃condition. When the ABA concentration was increased to5.0mg/L, we could see a significant mounting of CAT activity. But the concentration increased to7.5mg/L could not provide a higher mounting of CAT activity. To the treatment sprayed with10.0mg/L ABA, it only had a similar mounting of CAT activity compared with the plants sprayed with2.5mg/L ABA. So we thought that a comfortable concentration of ABA in increasing the CAT activity at4℃might be5.0mg/L.On the condition of4℃, the pattern of changes in the SOD activity was very similar to that of changes in the CAT activity. To increasing the SOD activity at4℃, spraying5.0mg/L ABA would be most acceptable.By RT-PCR and rubber tapping recovery and sequencing, we successfully cloned the Trichosanthes kirilowii CAT2gene and do the Quantitative PCR subsequently. On the condition of4℃, from0to5.0mg/L, as the concentration of ABA increased, the CAT2relative gene expression in plant leaves gradually increased. But there was not a further addition more than5.0mg/L as shown by the lower value of CAT2relative gene expression in7.5mg/L ABA treated plants when compared with that in5.0mg/L ABA treated plants, and more lower in10.0mg/L ABA treated groups. However, in chilling condition, ABA could help CAT2gene get more expression. At4℃, the CAT2relative gene expression had a high degree of positive correlation with the CAT activity. |
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