Study On Photosynthetic Characteristics Of 5 Superrior Liriodendron Tulipifera Clones

In this thesis, a test with randomized block design was conducted on 5 Liriodendron tulipifera clones and 1 Liriodendron sino-americanum clone under field conditions, taking 5three-year grafted seedlings of Liriodendron tulipifera clones as the study objects and 1Liriodendron sino-americanum clone which is currently widely researched as control. The determination of the photosynthetic indexes for the test materials such as diurnal variation of photosynthesis, light-response curves and CO2-response curves for three quarters was conducted with open gas exchange LI-6400 XT portable photosynthesis system at the Shandong test base of germplasm resource center, while the comparative analysis study was conducted on the water physiological indexes, growth indexes and chlorophyll content, etc of the six material from May to October, 2015. The thesis is aimed to acknowledge the relationship between photosynthetic characteristics and growth conditions of various clones of Liriodendron tulipifera, reveal the breeding potential and cultivation adaptability among various clones and screen the clone which has batter comprehensive index performance,laying a foundation for the popularization of superior clones. The study findings obtained through determination and analysis of multiple indexes are illustrated as follows:1. The diurnal variation of photosynthetic rate of various clones of Liriodendron tulipifera has different variation regularity in different quarters: in spring, the curves of No.27 and 28 are double-peak while others are single-peak; in summer and autumn, the curves of all clones are double-peak. The variation regularity of the maximum net photosynthetic rate in seasonal aspect is that summer > spring > autumn. There is a similar trend between the diurnal variation of Tr, Cond and that of Pn. The maximum net photosynthetic rates of No. 27 in three seasons are all greater than other clones. Liriodendron tulipifera clone has a smaller Cond, the mean of which of each clone in summer is 0.09. However, the mean diurnal variation of Cond of Liriodendron sino-americanum is 0.17, which is greater than that of Liriodendron tulipifera, with genetic factor accounting for the major cause.2. There are different light response curves in the same clone however different seasons.In spring and summer, the light saturation points are apparently higher and the light compensation points have no significant difference compared with autumn. The 5Liriodendron tulipifera clones have greater LSP values demonstrating high light effect, and higher compensation points demonstrating no strong ability of utilizing weak light. Generally,clones of No. 27 and 28 have greater apparent quantum yield and relatively smaller corresponding light compensation points, indicating relatively stronger ability of utilizing weak light. The photosynthetic-CO2 response curves of different Liriodendron tulipifera clones show different variation trends in different seasons. The photosynthetic-CO2 response curves determined in summer can show the growth adaptability of the plants in this area. No.27 and 28 have smaller variations in CE and greater with greater CE values in three seasons,demonstrating that these two clones have relatively higher utilizing ability for lower CO2 concentration.3. The variations of total chlorophyll, chlorophyll a and chlorophyll b of 5 Liriodendron tulipifera clones in seasonal aspect are: summer > spring > autumn(No. 27); and spring >summer > autumn(all other clones). The leaf water content of Liriodendron tulipifera clones in seasonal aspect is: spring > summer > autumn, while the variations of total chlorophyll,chlorophyll a and chlorophyll b of Liriodendron sino-americanum clone in seasonal aspect is:spring > summer > autumn, the leaf water content of Liriodendron sino-americanum(No. 1)is: summer > spring > autumn.4. Correlation analysis shows that: there is no significant correlation between net photosynthetic rates and chlorophyll content; the net photosynthetic rate has highly significant correlation with leaf water content, not significant positive correlation with specific leaf weight and not significant negative correlation with leaf water potential; there are significant or highly significant correlation between net photosynthetic rate and the indexes such as plant height, DBH(diameter at breast height), current branch length, current branch diameter and leaf number. Pn has high significant correlation with Tr, Cond, Ls, and WUE and highly significant negative correlation with Ci.5. Photosynthetic active radiation range is between 1000 ?mol?m-2s-1 and 1600?mol?m-2s-1. Atmospheric temperature range within 29–40°C is more benefit for the photosynthesis of Liriodendron tulipifera. It can be concluded through path analysis:excluding the disturbance of other factors, the net photosynthetic rate of Liriodendron tulipifera in summer is relevant to intercellular CO2 concentration and atmospheric temperature; Ta has greater indirect effect than direct effect to Pn. The conclusion can be drawn from decision coefficient: intercellular CO2 concentration and atmospheric temperature have inhibiting effect to net photosynthetic rate. And the result obtained from comprehensive analysis is that No. 27 and 26 have better comprehensive indexes for further breeding and popularization.6.Through the comprehensive comparison of growth indexes(plant height,Diameter of Breast Height and branch increment etc.) among 5 Liriodendron tulipifera clones,it can be concluded that No. 27 has the optimal performance followed by No. 26.