【Objective】 Investigating the cold resistance of four Ilex verticillata varieties provides a guidance and a reference for seedling promotion and research of these new varieties. 【Method】The physiological responses of four I. verticillata varieties (‘Red Sprite’, ‘Gray’, ‘Oosterwijk’ and ‘Winter Gold’) to low temperature stress were studied by exposing their branches to temperature treatments of 0 ℃, -7 ℃, -17 ℃ and -27 ℃ for 24 h. Cold resistance of the four varieties was compared. 【Result】The relative conductivity and malondialdehyde content of the four varieties increased with a decrease in temperature, and reached a maximum at -27 ℃. The low temperature semi-lethal temperatures for ‘Red Sprite’, ‘Gray’, ‘Oosterwijk’ and ‘Winter Gold’ were -26.38 ℃, -24.26 ℃, -29.19 ℃ and -20.04 ℃, respectively. Associated with the decrease in treatment temperature, there was an increase in the soluble sugar, soluble protein, and proline contents and osmotic regulators at > -17 ℃ (the soluble sugar of ‘Winter Gold’ reached its highest point at -27 ℃); however, the appearance of peak temperature for each variety was different. The H2O2 content and the activity of superoxide dismutase and peroxidase all reached their highest value at -17 ℃. The activity of the catalase enzyme increased sharply at -27 ℃, indicating that the three enzymes had a temperature effect on the scavenging of reactive oxygen species.【Conclusion】The cold resistance of ‘Oosterwijk’ and ‘Gray’ was stronger than that of the other two varieties as a whole. Through the comprehensive analysis of membership function and weight value, the order of cold resistance of the four I. verticillata varieties, from strong to weak was: ‘Oosterwijk’ > ‘Gray’ > ‘Red Sprite’ > ‘Winter Gold’.
【Objective】Golden leaf ginkgo is a bud-variety of Ginkgo bilobal L.,which is a new strain of ginkgo selected and bred in resent years. It has unique leaf color character and has a high ornamental and medicinal value. The leaves show a distinctive golden color from young ones in April and becomes green in summer and yellow in autumn. Because of its special leaf color and a long ornamental period, it can be used as an important foliage plant in spring and autumn. In recent years, with ginkgo entering the flowering stage, the crossbreeding work of ginkgo has been carried out, through the observation and analysis of the leaf color change characteristics of ginkgo seedlings, the theoretical basis is provided for the selection and application of better lines.【Method】One-year-old seedings of gold leaf ginkgo from Hubei Anlu were used,on the basis of the leaf shape, leaf color observation, the application of X-ray Rite chromatic meter measuring leaf color parameter values of L *, a * and b *, to calculate the reaction colour change of chroma h and C *, then measure the pigment content and photosynthetic characteristics index parameters, the correlation analysis and the related indicators.【Result】The golden leaf ginkgo’s shape is mainly fan-shaped, the leaf color is golden in April to May, light yellowish green in June, and it will become yellow again at the end of October.In the direction of L * dimension, most of the different color sites are concentrated in the middle position (L * value is in the range of 50-65), a * value is mainly concentrated in the negative area, and b * dimension sites generally show an upward trend.In the annual changes of pigment content, the variation trend of Chlorophyll a(Chla) content was first down, then up and then down slowly,reaching the maximum value in the middle of July. The change of chlorophyll b(Chlb) content as a whole,which increased initially and then decrease,and reached the maximum value in the middle of June.Chlorophyll T(ChlT) showed a trend of “descending-ascending-descending”, and the pigment content basically reached a very significant difference (P<0.01).The change of carotene(Car) content showed a trend of “decrease-increase”.The change trend of ChlT/Car is similar to that of ChlT, and the change of Chl a/b shows a downward trend of fluctuation. Throughout the year in April and October, low of content of Chla and high of both Chlb and Car, the leaf color is yellow. The increase of Chla/b and the decrease of Car are the main reasons for the change from yellow to green and the decrease in yellow degree.Therefore,the content and the ratio of each pigment comprehensively affect the expression of leaf colors.Both Chla and Chlb were negatively correlated with chromatic aberration parameters L *, a *, b * and C *, and positively correlated with Car which was significantly positively correlated with a * and b *, respectively.In the variation of photosynthetic characteristic values, the highest value of net photosynthetic rate (Pn) was at 9:00,and the lowest value was at 13:00.After that,there was another peak at 15:00,showing obvious double peaks and the phenomenon of “lunch break”. The stomatal conductance (Gs) also showed obvious bimodal peaks,which appeared at 9:00 and 15:00 respectively,and it was higher in the morning than that in the afternoon. While the transpiration intensity (Tr) showed a regular variation,which was at a high level from 9:00 to 13:00 on the whole, but it dropped sharply after 15:00,which was the lowest value in a day.The diurnal variation of Ci is “W” type, that is, there are two valleys in one day, respectively at 11:00 and 15:00,the highest in 13:00. Pn was negatively correlation with Chla and Car,and positively correlation with Chla/b.The correlation between other photosynthetic characterstic values and pigment contents was not obvious.【Conclusion】The shape of leaves is mainly fan-shaped at one-year old seedings of golden leaf ginkgo and the leaf color is golden in April-May, changing color in June, gradually turning green, and yellow in October.Color difference parameter between April and May, high brightness per plant increased, the green color became lighter and the yellow deepened with time. The correlation analysis shows that pigment content was closely related to leaf colors, but the correlation between photosynthetic characteristic value and pigment contents was not closely related.
【Objective】We study the phenological characteristics of the early-flowering stage of several varieties of ornamental crabapple, to explore the internal relationship between the flowering stage and temperature, and to reveal the differences and changes in flowering stability at a variety level. 【Method】Four-year phenological data from 67 varieties of ornamental crabapple were analyzed to determine the stability of multiple ornamental crabapple varieties, and the results of standard deviation of phenology (σ) of multiple varieties of ornamental crabapple were studied using temperature data over many years. 【Result】From 2014 to 2016, there was a strong correlation of the date sequence of early flowering with that of 2013. The σ value of late-flowering varieties was higher than that of early-and mid-flowering varieties. There was a significant negative correlation (P<0.05) between the σ value of the early florescence and middle florescence; this correlation was also noted between the σ value of the late florescence and days with temperature below 6 ℃ from October 1st to December 1st in the year before florescence, between the σ value of the late florescence and days with a temperature below 4 ℃ (P<0.05) from October 1st to February 1st in the year before florescence, and between October 1st to March 1st in the year before florescence. 【Conclusion】 A low temperature has an important effect on the stability of ornamental crabapple at the early-flowering stage. The varieties in the early-and mid-flowering stage required a lower temperature than that required at the late-flowering stage, and the time limit for breaking dormancy was more strict. In contrast, the stability of the early-flowering sequence among the late-flowering varieties was lower.
