| Dalbergia odorifera T.Chen,named as Hainan rosewood,belongs to Papilionaceae Family and Dalbergia Genus.Its heartwood is precious and also with important pharmaceutical value.As the uniquely precious species in Hainan Province,efficient cultivation of D.odorifera has important social implications and economic benefits.Since it's long rotation,high risk of cultivation and insignificant short term economical return druing the process of plantation cultivation,high quality heartwood production are thus far behind the market demand.Therefore,effcient silvcultural measures are urgently needed for heartwood cultivation of D.odorifera plantation.Based on this,the present study conducts four experiments,comprising big seedling transplantation,pruning,potassium fertilization on young and middle aged trees as well as ethephon injection on trunk,to explore the effects of different silvcultural measures on tree growth,physiological metabolism and heartwood formation.The present study would provide reliably theoretic basis and technological support for the efficient cultivation of D.odorifera.The main results are as follows.Pruning treatments had no significant effect on DBH,tree height and individual volume within one year of D.odorifera.Both light pruning?D?and heavy pruning?H?treatments improved Pnmax of D.odorifera.Compared with CK,Pnmaxs of D and H treatments increased by 28.3%and 8.18%,respectively.There was no significant difference for optical system?maximum photochemical quantum yield?Fv/Fm?among the treatments.However,both Fv/Fms of D and H treatments were larger than CK.One year later after treatments,the photosynthetic pigment content of H treatment was much higher than that of CK and D treatment.Besides,IAA and ABA content of all pruning treatments were declined with time,but trans-Zeatin-riboside?ZR?content of D and H treatments were significantly higher than that of CK.In addition,pruning treatments had no signifcant effect on basic density,green density,absolute moisture content and relative moisture content of heartwood timber.However,the heartwood ratio of H treatment was signifcantly higher than that of CK and D treatment.It increased 1.59 and 1.24 times over the control,respectively.Correlation analysis showed that there was a significant positive correlation between the resistance intensity and heartwood ratio in D.odorifera after pruning.Compared to CK,root pruning and half crown pruning treatments had no significant effect on tree growth of D.odorifera.On the contrary,half crown and full crown transplantating suppressed tree growth.The maximal net photosynthetic rate?Pnmax?of root pruning treatment was greater than that of other treatments.The light saturation point?LSP?of half crown treatment was the higheast and reached 2371.429?mol·m-2·s-1.The photosynthetic pigment content of root pruning and half crown pruning was higher than that of CK.The specific leaf area?SLA?differed signicantly among the treatments,the order was:root pruning>half de-crown>half de-crown transplanting>CK>full crown transplanting.The maximal value was 16.20%,22.39%,34.90%and 150.64%higher than other treatments sequentially.The IAA content of half de-crown and full crown transplanting was significantly higher than that of CK in the early stage of treatments and lower at the late stage of treatments.The ABA content was also lower than that of CK in the later stage.At the preliminarily stage of treatment,protective enzyme and PAL activity decreased in the order of de-crown transplanting,root pruning,half de-crown,half de-crown transplanting and CK,while MDA content showed the inverse trend.One year later after treatment,both SOD and PAL activities declined significantly while MDA content increased gradually.No signifcant difference was found for all heartwood basic traits among all transplanting treatments.There was a significant positive correlation between resistance and heartwood ratio for each treatment.Therefore,in the plattation cultivation process of D.odorifera,the root pruning and half de-crown transplanting measures can be selected to promote the accumulation of photosynthetic substances by the physiological process,such as photosynthesis.The potassium fertilization prompted the growth of D.odorifera.The DBH increments??D?of K1 and K2 were higher that CK by 14.11%and 17.78%,respectively,but there was no significant difference between them.The tree height increments??H?of K1 and K2 were higher than CK by 23.32%and 68.58%,respectively,and the individual volume increments??V?increased with the increasing of potassium fertilization,and individual volume increments of K2 was 1.03 times higher than that of CK.Pnmax reached the highest in K2treatment,it was 132.35%higher than that of CK.Photosynthetic pigment content,Fm,Fv and Fv/Fm all increased with the increasing amount of potassium fertilization.The leaf full nitrogen?N?and potassium?K?content of K1 and K2 differed signifcantly from CK,while no obvious difference was observed for leaf full phosphorus?P?content among all treatments.Both N and K content presented the increasing trends as the increment of potassium fertilization.The potassium content of K1 and K2 was 18.54%and 24.68%higher than those of CK,respectively.Furthermore,potassium fertilization increased the content of ZR and IAA of D.odorifera.In general,potassium fertilization had no signifcant effect on heartwood basic traits.The oil extraction rate of heartwood showed little positive correlation with the anmount of potassium fertilization,however,no significant difference was found.Potassium fertilization treatment had no signifcant effect on the composition of essential oil.The content variation of each compoent was also low.Only did the nerolidol content of K1 and K2 treatments increase by 10.62%and 6.20%than that of CK,respectively.Thus,the application of potassium fertilizer of 2000g·tree-1 can effectively increase the growth level of D.odorifera.Among the 3 ethephon treatments,the?D of E0.1%and E0.5%treatments was larger than that of CK by 8.97%and 6.07%,respectively.Both?H and?V of E2.5%treatment were lower than those of CK with a decrease of 67.39%and 59.33%,respectively.E0.1%and E0.5%treatments had positive effect on the photosynthesis of D.odorifera,Pnmax,net photosynthesis?Pn?,stomatal conductivity?Cond?,Fv/Fm and photosynthetic pigment content all increased after ethephon treatments.Leaf dry weight,leaf area and SLA showed decrasing trends with the inceasing amount of ethephon.As to SLA,E0.1%and E0.5%were 23.29%and 11.34%higherand E2.5%was 9.81%lower than CK.WUE had a positive correlation with ethephon concentration.At the early stage of treatment,there was a positive correlation between ABA content and ethephon concentration,while at the later stage,ABA of E0.5%treatment was lower at the late period.However,both protective enzyme and PAL activity of E0.5%treatment were higher than other treatments.There were significant differences for green heartwood timber density after treated by ethephon.The maximal density(1.036 g·cm-3)was found in E0.5%treatment,and was higher than that of CK by 7.4%.Both the absolute and relative moisture content of E2.5%treatment were the highest.The percentage of trees with heartwood increased with the increasing ethephon concentration,and reach 100%for E2.5%treatment.The oil extraction ratioofethephon treatments ranged from 1.484%to 2.23%and were all larger than that of CK.The highest relative content of nerolidol was found in CK and it was higher than E0.1%,E2.5%,and E0.5%in order.The Bisabolol A content was larger for ethephon treatments than that of CK,and the maximum was observed in E2.5%?1.124%?,which was 36.59%higher than that of CK.Both?-farnesene and pterocarpin content was found.and the highest was in E0.1%and the lowest was in E2.5%treatment.Generally,the main composition and content did not differ signifcantly among treatments,and ethephon treatments had positive effect on heartwood formation.Correlation analysis also showed that there was a significant positive correlation between the resistance of ethylene treatments and ratio and oil yield of heartwood.Therefore,heartwood formation could be accelerate by injecting 100 ml ethephon?2.5%?per tree. |
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