| Dalbergia odorifera T.Chen,also known as Hainan rosewood,is widely cultivated in south China due to its precious wood properties and high medicinal value of it's heartwood.The fact of fully blooming and fruiting at very young stage consumes a lot of nutrition of the very young trees and inhibits their vegetative growth and even the wood production of D.odorifera.On the other hand,increasing seed yield of fine germplasm trees can satisfy the increasing demand of high quality seeds for high quality seedling production.Therefore,it is of great practical significance to study the effects of regulatory measures on the vegetative and reproductive growth of D.odorifera.In this paper,the effects of different amongt nitrogen,phosphorus and potassium gradients applications on vegetative and reproductive growth of very young trees,and different N,P and K ratio,NPK compound fertilizer amount and kinds and dosage of plant growth regulators on vegetative and reproductive growth of young and middle-aged trees were studied.The main findings are summarized as follows:?1?Nitrogen application could obviously promote the vegetative growth?p<0.05?,and tree height,ground diameter,DBH and crown width with N application were significantly higher than those without application.All of these indicators showed an overall upward trend to promote young tree vegetative growth with the increase of N application.Low N and high N promoted reproductive growth,medium N suppressed reproductive growth.Among all treatments,92.8 g N·plant-11 significantly promoted vegetative growth while reduced the flowering plant rate,flowering branch rate,fruiting branch rate,inflorescence,small fruits number and fruits weight.?2?There was no significant difference in vegetative growth among 7 phosphate treatments?p?0.05?.The application of P could promote flowering plant rate,fruiting plant rate,flowering branch rate,fruiting branch rate,the inflorescence number,and the difference of the flowering plant rate,fruiting plant rate and flowering branch rate were significant?p<0.05?.In all treatments,120 g P2O5·plant-1 was the most favorable to the reproductive growth for promoting the flowering plant rate,fruiting plant rate,flowering branch rate and number of small fruits.?3?The effect of potassium application on the vegetative and reproductive growth was significantly different?p<0.05?.K application could promote the vegetative growth?the height,DBH and ground diameter?.Vegetative growth increased largely with low P applications and then tended to be steady with P fertilizer amount increased.36?72 and 108 g·K2O·plant-1 were significantly different with the control without K application,but there was no significant difference between the 3 K treatments.The reproductive growth was increased firstly with low K application and then inhibited with high K application.18 g·plant-1 K2O significantly increased the flowering branch rate and infructescence number,36 g·plant-1 significantly promoted infructescence number,small fruits number,inflorescence length and diameter.However,72 and 108 g·plant-1 significantly decreased the flowering plant rate,fruiting plant rate and fruiting branch rate.Considering all of the above,to the very young trees,72 g·plant-1K2O was the best potassium application to control reproductive growth and promote vegetative growth.?4?There were significant differences on vegetative and reproductive growth of D.odorifera among different N,P and K ratio treatments?p<0.05?.Nitrogen(185.6 g N·plant-1)application treatment was helpful for vegetative growth,and promoting diameter growth for timber forest cultivation.In this treatment,the ratio of vegetative branch,small leaf number and leaflet width on vegetative branches were increased by 40.25%,21.75%and 9.52%,meanwhile,inflorescence diameter and biomass were decreased by 12.75%and 48.63%more than those in the control,respectively.While the applications of P(120 g P2O5·plant-1)and P mixed with K(120 g P2O5+120 g K2O·plant-1)were more appropriated for breeding purpose,because the ratio of vegetative branch was decreased by 47.96%and 46.84%,respectively.When N,P and K were mixed together(185.6 g N+120 g P2O5+120 g K2O·plant-1)and applied,the vegetative and reproductive growth were both enhanced significantly?p<0.05?,and the ratio of vegetative branch,length of vegetative branch,small leaf number,leaflet length,leaflet width,branch biomass,inflorescence number and inflorescence biomass were increased by 26.04%,68.16%,32.98%,15.20%,11.40%,83.60%,54.20%and 49.84%,respectively.Thus,the vegetative and reproductive growth of D.odorifera can be regulated through formula fertilization?biased to nitrogen or phosphorus and potassium?.?5?Different amount NPK compound fertilizer applications could obviously affected the vegetative growth and reproductive growth?p<0.05?.500 g·plant-11 compound fertilizer application?N:P2O5:K2O=16:16:16?could significantly increase the inflorescence number.After 1000 g·plant-1 treatment,fruits weight and seeds weight were the best among all treatments,significantly higher than those in 2000 g·plant-1 application treatment.2000g·plant-1 significantly reduced the flowering branch rate and hundred fruits weight.?6?The effects of different kinds and dosages of growth regulators on the vegetative growth and reproductive growth were significantly different?p<0.05?.Foliar application of 200mg·L-1?100 mg·L-1GA3 and 500 mg·L-1 6-BA promoted vegetative growth greatly,and inhibited reproductive growth simultaneously,while foliar application of 1500 mg·L-1?2000mg·L-11 PP33333 and 50 mg·L-11 6-BA promoted the reproductive growth.200 mg·L-1 GA3 had the best inhibitory effect on reproductive growth,because the flowering branch rate and inflorescence number decreased significantly after treatments.100 mg·L-11 GA3 increased significantly branch length,branch diameter,leaf number and leaf weigh.2000 mg·L-11 PP333increased significantly flowering branch rate,the number and diameter of inflorescence and thousand seeds weight. |
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