Research On Physiological Characteristics And Family Selection Of Toona Ciliate

Toona ciliate, as a precious furniture wood species with good economic value and broad development prospect, has the reputation of "Chinese Mabogany", and is ranked into category Ⅱ nationally protected species. With the rapid development of furniture industry, wood products of Toona ciliate cannot meet the great need of market, which demonstrates that the science and technology support of Toona ciliate nursery and silviculture base construction cannot meet the huge need of scientific research. To solve the urgent problem, it is essential to carry out researches on water physiological characteristics, photosynthetic physiological characteristics and comprehensive family selection of Toona ciliate.In this study, by using Toona ciliate clones and families primarily selected by Hunan Academy of Forestry as material, and adopting completely randomized block design as experimental design method, we probed into water physiological characteristics of Toona ciliate clone seedlings, photosynthetic physiological characteristics of Toona ciliate families, the increment of tree height, DBH, crown and wood basic density of Toona ciliate families and the correlation, and carried out comprehensive selection of superior families. The results were as follows:1. Responses of drought stress on leaf physiological characteristics of young Toona ciliata clones Seedlings showed as follows:(1) Severe stress (17d continuous water break) resulted in the occurrence of the lowest RWC and the highest chlorophyll concentration and content. Under moderate stress (12d continuous water break) and severe stress (17d continuous water break), there was an evident increase in PMP, SOD content, POD content, and MDA content. The Proline content of seedlings under severe stress (17d continuous water break) was larger than three times of that under other3stress treatment. There was a climbing of the protein content of seedlings from CK (2d continuous water break) to moderate stress (12d continuous water break), and then sharply declined under severe stress (17d continuous water break).(2) Under drought stress treatments, clone17and18held higher chlorophyll concentration, and clone19and20instead. There was no significant difference in RWC, PMP, SOD content, POD content, MDA content, Proline content and protein content.(3) There was a significant difference in RWC between3test periods, with the order of the value that period Ⅱ>period Ⅲ>period Ⅰ(P><0.05). There was a significant difference in chlorophyll concentration and content between3test periods, with the order of the value that period Ⅲ>period Ⅱ>period I(P<0.05). There was no significant difference in SOD content between3test periods, with a slight " down-and-up" trend that period Ⅰ>period Ⅲ>period Ⅱ. There was a significant difference in POD between3test periods, with a down trend that period Ⅰ>period Ⅱ>period Ⅲ(P<0.05). There was a "down-and-up" trend in PMP in3test periods, with the order of the value that period Ⅲ>period Ⅰ>period Ⅱ. There was significant difference in MDA content, with an order that period Ⅲ>period Ⅰ>period Ⅱ(P<0.05). The Proline content increased gradually with the continuous test periods. The protein content obey a rule that "sharp increase-and-decrease".(4) From the leaf physiological comprehensive information obtained by principal component analysis, we could draw a conclusion that chlorophyll was the key factor to maintain the vigor of seedlings through the whole test and the main factor to respond to the drought stress. Meanwhile, the membrane system and antioxidant enzyme system were also important.2. Results of photosynthetic physiological characteristics study of Toona ciliate were as follows:(1) The light saturation point, compensation point and apparent quantum efficiency of Toona ciliate were1177.8μmol·m-2·s-1,20.0μmol·m-2·s-1and0.0345respectively, which indicated that Toona ciliate could make better use of low light.(2) There was a positive significant relationship between photosynthetic rate and transpiration rate, active photosynthetic radiation, air temperature and leaf temperature. There was a negative significant relationship between intercellular CO2concentration and photosynthetic rate and transpiration rate. The blade water deficit was seriously influenced by relative air humidity. The relative air humidity was seriously influenced by air temperature and light intensity. There was a significant negative correlation between relative air humidity and transpiration rate.3. The study of family selection of Toona ciliate showed the results as follows:(1) There was a significant difference in tree height growth between20tested Toona ciliate families and the highest height of5.4m belonged to TC02. The heritability of tree height was at moderate level of0.4928, which indicated that there was small individual difference within family.(2) There was an obvious difference in DBH growth between20tested Toona ciliate families and the biggest DBH of5.63cm belonged to TC03. The heritability of DBH was0.5838, larger than that of height.(3) The biggest crown width of2.93m belonged to TC03and there was no evident difference between families.(4) There was an obvious difference in individual volume growth between20tested Toona ciliate families and the biggest individual volume of0.0185m3belonged to TC02. The heritability of individual volume was0.5981, which indicated that there was small individual difference within family.(5)5families with good growth traits were screened out as TC02, TC03, TC04, TC12and TC20. The basic wood density of tested families varied from0.7147g.cm-3to0.5232g.cm-3and4families with larger basic wood density were selected out as TC02, TC03, TC12and TC20.(6) The basic wood density variation of28a Toona ciliate followed the mode that slowly increasing curved from pith to outside. There was no significant difference between annual rings.(7) After choosing the breeding strategy that combining growth condition as main selection factor with wood property improvement as secondary target to select good Toona ciliate families comprehensively, we selected out4families with both good growth and wood property, which were TC02, TC03, TC12and TC20.