毛竹新竹爆发式生长期的碳输入及其水驱动机制研究

[Objective]Moso bamboo(Phyllostachys edulis)is China's most widely distributed and artificially planted bamboo species,characterized by fast growth,versatility,and outstanding ecological and economic benefits.The high growth rate,or"explosive growth,"guarantees these benefits.However,the lack of leaves means the new bamboo is non-autotrophic and may rely on external sources of non-structural carbon(NSC)for growth.Previous studies suggested that stored carbon in the mother culm is the carbon source for newly sprouted culm growth.However,the contribution of newly produced carbon from the mother culm leaves during"explosive growth"and the driving force of external carbon sources into the newly sprouted culm remain unclear.[Methods](1)Continuous dynamic monitoring of bamboo shoot height during the"explosive growth"period using thermal infrared cameras to obtain hourly scale height growth data;(2)Examining the dynamics of non-structural carbon content of mother culm stalks during the growth period of new culm by breaking the whip and removing leaves in the"mother culm-rhizome-new culm"experiment,and exploring the carbon stored in the mother culm and the transfer of new carbon fixed by photosynthesis in mother leaves to the newly sprouted culm;(3)Monitoring bamboo rhizome sap flow using TDP+ technology to study the water use characteristics of new bamboo during culm growth;(4)Exploring the synergistic carbon and water transport mechanisms and the influence of carbon and water on the growth of newly sprouted culms by combining the characteristics of growth of newly sprouted culms,the simultaneous monitoring of bamboo rhizome sap flow,and the dynamics of non-structural carbon content of newly sprouted culms.[Results](1)During the"explosive growth"period,the average daily height growth of newly sprouted culms showed a slow-fast-slow pattern,reaching maximum height growth(about 70 cm)around April 25.Height growth was significantly higher at night(30.13±8.21cm)than during the day(20.64±5.97cm),with average height growth at night being 9.5 cm higher than during the day.(2)Among the carbon transferred from the mother bamboo to the newly sprouted culm,stored old carbon accounted for about 50%-55%,and new carbon produced by leaf photosynthesis accounted for about 45%-50%.This indicates the importance of new carbon produced by leaf photosynthesis of the mother culm for the growth of the newly sprouted culm and the possible existence of an alternating supply of new and old carbon from the mother culm to the newly sprouted culm.It was found that the type of carbon supplied by the mother culm to newly sprouted culm differed between on-year and off-year,with starch dominating in the off-year(57%)and soluble sugars in the on-year(64%).Soluble sugars accounted for about 90%of the total NSC content,and starch accounted for 10%.Soluble sugars were mainly consumed during the"explosive growth"period.(3)The daily dynamic pattern of sap flow in the mother culm showed a typical unimodal pattern,while the newly sprouted culm showed the opposite pattern of"low day and high night"before leaf development and the same pattern as the mother culm after leaf development.The flow pattern of the bamboo rhizome before leaf development showed the same daily pattern as that of newly sprouted culms,with flow from the newly sprouted culm to the mother culm during the daytime and from the mother culm to the newly sprouted culm during nighttime("day-out and night-in").This indicates that during the explosive growth of newly sprouted culms,bamboo forest water resources were allocated more to the mother bamboo during the daytime and to the newly sprouted culm during nighttime.(4)The mother culm transferred carbon to the newly sprouted culm during the explosive growth period,but the newly sprouted culm required more carbon during this period than the mother culm transferred to the newly sprouted culm(137.63 mg.g-1 vs.30.21 mg.g-1).This suggests that the mother culm is not the only carbon source for the newly sprouted culm but may also include carbon stored in the underground rhizome system of the new culm and carbon produced by photosynthesis of the newly sprouted culm stems and culm sheaths.A significant positive correlation was found between the daily accumulation of positive sap flow from the bamboo rhizome(mother culm to new culm)and the NSC content of newly sprouted culms,suggesting a possible water synergy in the acquisition of carbon by newly sprouted culms.[Conclusion]The findings from this study on the"explosive growth"phase of moso bamboo shoots indicate that the carbon source for new shoots includes not only stored carbon from mother bamboo but also newly fixed carbon from mother bamboo foliage.Additionally,the results reveal water's collaborative role in the carbon influx into new shoots.These findings provide valuable insights into the physiological mechanisms underlying the explosive growth of moso bamboo and have significant implications for the efficient cultivation and management of this species.