| Fokienia hodginsii (Fokienia hodginsii (Dunn) Henry et Thomas) is endemic cupressaceaeconifer species in China, which was found first by the British in Yongtai County in Fujian Province.They could be called Alias jian cypress,Yunnan cypress. It is a single specie of Fokienia hodginsiispecies and is chinese first batch of rare species for key protection. However, the lack of Fokieniahodginsii resources, long-term excessive use and unreasonable exploitation were making thenatural forests of Fokienia hodginsii destroyed severely, only a small amount of Fokienia hodginsiiexisted like distribution, and most of them were remaining in the remote rural. Since the1950s and1960s, Fujian was the first Province to create Fokienia hodginsii plantation. With the carefulmanagement, protection and development form managers, Fokienia hodginsii resources have gotprotection and development.Fujian is located in the hills zone, the cultivation of Fokienia hodginsii showed differentadaptive capacity in different areas, especially in the barren land, less or lack of water land near thetop of the hill zone, the survival rate of Fokienia hodginsii and growth conditions suffered a seriousconstraint, where water was an important factor restricting the growth and development. Therefore,breeding a number of Fokienia hodginsii clones with adaptation ability to environment stronglyand ability of growth quickly was important research content to expand the plantation of Fokieniahodginsii and to protect the rare species.In this study, their leaves in vitro from different Fokienia hodginsii clones were treateddrought stress and the analysis of photosynthetic characteristics to different Fokienia hodginsiiclones were conducted, which aimed to elect a number of Fokienia hodginsii clones with thefast-growing character, adaptation ability to environment.According to Fokienia hodginsii clones'growing conditions in our study, different Fokienia hodginsii clones have been divided into threegroups, fast-growing plants (Ⅰgroup),moderate-growing plants (II group),slow-growing plants(III group).Then their leaves in vitro from different Fokienia hodginsii clones were treated droughtstress and the analysis of photosynthetic characteristics to different Fokienia hodginsii clones wereconducted.1The results of their leaves in vitro from different Fokienia hodginsii clones weretreated drought stress as follows:The experimental results have showed that: Relative water content, Membrane permeability,MDA content, Proline content, SOD enzyme activity varied significantly from Fokienia hodginsiiclones in different groups of different-growing conditions. Among them, fast-growing plants (I group) owed higher relative water content in the initial, which could reach85.7％; Relative watercontent of81.8％from Moderate-growing plants (II group), followed by fast-growing plants(group I);With the drought stress time of their leaves in vitro extend (up to8h time), the relativewater content of fast-growing plants (I group) and slow-growing plants (III group) decreased by21.1％and27.8％, while the overall level of relative water content from moderate-growing plants(II group) decreased by14.5％;With further stress, the relative water content of moderate-growingplants (II group) decreased less than the other two groups' plants, which was showed the ability ofwater conservation and the ability to fight against drought stress performance better than the othertwo groups' plants,plus good tolerance of environmental moisture loss.Changes of membrane permeability and MDA content showed that when the leaves in vitroencountered drought stress, the loss of water closely was related to the increased membranepermeability and MDA content in plants. In three different clonal groups during drought Stress,MDA and membrane permeability increased by a wide margin; when the drought stress time wasup to12hours, fast-growing plants (I group), moderate-growing plants (II group) andslow-growing plants (III group) increased by380.9％,220.5％,494.3％; During drought Stressin the early time, membrane permeability and MDA concentration of moderate-growing plants (IIgroup) showed declining trend among groups; At present the overall level of SOD activity ofmoderate-growing plants (II group)showed an upward trend and could be maintained at a certainlevel, which was also showed that this plants from moderate-growing group can play aself-regulating functions, reducing the plasma membrane damage and resulting in a decline in theconcentration of MDA content by increasing the activity of SOD protective enzymes.With the drought stress time prolonged, the proline content in the Fokienia hodginsii clones'groups continued to increase and response rapidly to the drought stress(the drought stress time upto2hours), which increased by a wide margin in moderate-growing plants (II group) andslow-growing plants (III group); While slow-growing plants (III group) increased greatest than theother two groups, which was followed by moderate-growing plants (II group);However, the prolinecontent of fast-growing plants (I group) in the drought stress time of4h increased by a big marginand responsed to drought stress slow.From the changes range of the SOD enzyme activity we can know that the SOD enzymeactivity of fast-growing plants (I group), moderate-growing plants (II group) and slow-growingplants (III group) declined by68.6％,12.5％,27.4％; The changes range of the SOD enzymeactivity: moderate-growing plants (II group)<slow-growing plants (III group)<fast-growing plants(I group), which indicated that the high ability of moderate-growing plants (II group) to scavengereactive oxygen and oxygen-free radicals and the high ability to defense against the damage caused by the drought stress;the SOD enzyme activity of slow-growing plants (III group) wasn't betterthan moderate-growing plants (II group), but the SOD enzyme activity was followed byfast-growing plants (I group).The relativity of the physiological indicators from Fokienia hodginsii clones was closedsignificantly, which included relative water content, membrane permeability, malondialdehyde,proline, the SOD enzyme activity. What was said above,when the leaves in vitro encountereddrought stress, the body of the leaves was a complex physiological and biochemical reactions; Inclonal plants osmotic adjustment system and the protective enzyme of the membrane had verygood synergy to defense plants by in vitro drought damage.2The experimental results of Photosynthetic characteristics:Net photosynthetic rate and light intensity of Fokienia hodginsii clones was a significantcorrelation of quadratic curve, and the R value of the photosynthetic curve in the three groups ofplants of fast-growing plants (I group), moderate-growing plants (II group) and slow-growingplants (III group) were0.9above, while the light intensity response curve was well fitted. Withlight intensity enhancement, net photosynthetic rate showed an upward trend, and the maximum ofnet photosynthetic rate was that fast-growing plants (I group)>moderate-growing plants (IIgroup)>slow-growing plants (III group), while the overall photosynthetic capacity of fast-growingplants (I group) performanced well.Under the same growth conditions, the light compensation point and light saturation point inevery groups of plants was significantly different, which was showed the different ability to utilizehigh light level and low light level. The overall level of the light compensation point offast-growing plants (I group) was lower, which was also showed the higher ability to use low light.In the three groups of Fokienia hodginsii clones, the range of the light saturation point was stablemaintained from1200μmol/(m2s) to1350μmol/(m2s), the light saturation point ofmoderate-growing plants (II group) showed the maximum can be achieved up to1321μmol/(m2s), which was followed by fast-growing plants (I group). The overall level of light saturation pointof slow-growing plants (III group) was lowest level.In the groups of Fokienia hodginsii clones, the average net photosynthetic rate of plants wassignificantly difference. The net photosynthetic rate of the different clonal groups performancedthat fast-growing plants (I group)>moderate-growing plants (II group)>slow-growing plants (IIIgroup). With the upward trend of growth, the average net photosynthetic rate between the differentgroups indicated an upward trend. The net photosynthetic rate was closely associated with the RuBP enzyme activity, transpiration rate, stomatal conductance, the efficiency to utilize water,allof them were significantly different. The correlation between the average net photosynthetic rateand the RuBP enzyme activity were the highest and showed an upward trend with the upwardgrowth of plants improvement.In the different colnal groups, the efficiency to utilize water performanced thatmoderate-growing plants (II group)>fast-growing plants (I group)>slow-growing plants (III group).The results of experiments showed that the efficiency to utilize water of moderate-growing plants(II group) and water-saving ability was higher,which was better than the others. Those plants weresuitable for growth and improvement in the unwatered environment. With the comprehensiveanalysis of Fokienia hodginsii clones groups' Photosynthetic indexes, each clonal group variedsubstantially, and the overall photosynthetic capacity of fast-growing plants (I group) performancedwell,which was much higher than the other two groups, belonging to fast-growing plants. Theoverall photosynthetic capacity of moderate-growing plants (II group) was lower than the overallcapacity of fast-growing plants (I group), while the efficiency to utilize water was much higherthan the other groups, belonging to water-saving plants. |
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