| Walnut(Juglans regia L.)is a main economic tree species in China.,It has played an active role in desert management and ecological environment improvement in mountainous areas.But the branches of walnut have poor cold resistance during overwintering,and it is vulnerable to bear low temperature and late frost during spring germination and leaf spreading.Ethephon is an important plant growth regulator,widely involves in plant growth and development,and plays an important role in plant response to stress.The variety ‘Nonghe 1' of precocious walnut was employed as the test materials,the experience sprayed different concentration of ethephon in the spring or autumn to observe walnut budding and female stamen development period and determine leaf chlorophyll content,net photosynthetic rate,antioxidases activity of leaves and branches,osmotic adjustment matters content and starch content.Therefore,it is effective to provide reference for avoiding the late frost damage in the spring and improve cold resistance of branches in the winter through studying effects of ethephon on delaying the walnut spring bud,promoting the fallen leaves and the cold resistance of leaves and branches.The research results were as follows:1.Spraying different concentrations of ethephon could delay walnut germination and flowering in spring dormant period.Compared with the control,0.25 mg/L,0.50 mg/L and 1.00 mg/L ethephon could delay walnut germination for 1 d,3 ~ 5 d and 4 ~ 7 d,respectively.The germination of male flowers was delayed about 5 ~ 7 d,7 d and 7 d,respectively.The exposure period of pistil ovary was delayed by 2 ~ 3 d,3 ~ 4 d and 4 ~ 5 d,respectively.2.Spraying ethephon with different concentrations could obviously reduce the male inflorescence length and increase the male inflorescence malformation rate in spring dormant period.Compared with the control,0.25 mg/L,0.50 mg/L and 1.00 mg/L ethephon reduced the stamen length by 37.26%,44.49% and45.63%,respectively.The rate of stamen malformation increased by 18.57%,43.16% and 65.49%,respectively.3.Spraying different concentrations of ethephon could promote early defoliation of walnut leaves in the early stage of the fallen leaves.Compared with the control,spraying 0.50 mg/L and 1.00 mg/Lethephon made walnut shed leaves 5 and 13 days earlier,respectively.4.Spraying ethephon with different concentrationscould reduce leaf net photosynthetic rate and increase leaf transpiration rate in the early stage of the fallen leaves.Compared with the control,0.25 mg/L,0.50 mg/L and 1.00 mg/L ethephon reduced Pn by 11.97%,16.73 and 21.60%,respectively.Transpiration rates were significantly increased by 12.89%,23.62% and 37.96%,respectively(P < 0.05).5.Spraying ethephon with different concentrations in the early stage of autumn deciduous leaves could reduce the antioxidases activity and membrane lipid peroxidation products in leaves at the middle stage of deciduous leaves,and improve the osmotic adjustment matters content.Compared with the control,SOD in the leaves of 0.25 mg/L,0.50 mg/L and 1.00 mg/L decreased by 6.94%,8.92% and 6.87%,respectively.POD activity was highly significantly decreased by 39.83%,66.94% and 68.57%(P < 0.01).MDA content was highly significantly decreased by 1.13%,19.74% and 32.12%,respectively(P < 0.01).The proline content of 0.25 mg/L and 1.00 mg/L leaves were increased by 7.18% and 3.86%,The soluble sugar content of 0.25 mg/L and 1.00 mg/L leaves were increased by 2.56% and 6.79%,respectively.Compared with the control,the soluble protein content in the leaves of 0.25 mg/L,0.50 mg/L and 1.00mg/L were significantly increased by 13.09%,14.11% and 21.33%,respectively(P < 0.05).The membership function method was used to evaluate the cold resistance of leaves,and the order from high to low was 0.25 mg/L > 0.00 mg/L > 1.00 mg/L > 0.50 mg/L.6.Spraying ethephon with different concentrations in the early stage of autumn deciduous leaves could improve the antioxidases activity in branches in dormant period,reduce MDA content,and increase the osmotic adjustment matters content and starch content.Compared with the control,1.00 mg/L ethephon increased SOD by 5.34%.POD was highly significantly increased by 2.94 times and 2.90 times by 0.25 mg/L and 0.50 mg/L respectively(P < 0.01).CAT activity of branches was highly significantly increased by 21.60% and 78.06% respectively by 0.50 mg/L and 1.00 mg/L ethephon(P < 0.01).0.25 mg/L and 0.50 mg/L ethephon reduced MDA by 4.00% and 0.07% respectively.0.25 mg/L and 0.50 mg/L ethephon significantly increased proline content and soluble protein content by 1.64 times and 1.48 times,9.80% and 10.01%,respectively(P < 0.01).The starch content of 0.25 mg/L,0.50 mg/L and 1.00 mg/L ethephon were highly significantly increased by 73.48%,38.82% and 37.81%,respectively(P < 0.01).The cold resistance of branches was evaluated by membership function method,and the order from high to low was 0.50 mg/L > 0.25 mg/L > 0.00 mg/L > 1.00 mg/L.7.To sum up,the comprehensive evaluation by applying the membership function showed that the spraying of 0.25 mg/L ethephon on leaves had the strongest cold resistance,and the spraying of 0.50 mg/L ethephon on branches had the strongest cold resistance in autumn.Therefore,0.25 mg/L ethephon was recommended for production. |
PDF Full Text Request