古尔班通古特沙漠西南缘多枝柽柳生理特性对沙堆不同堆积阶段的响应

Response of physiological characteristics of Tamarix ramosissima to different accumulation stages of cones in the southwestern margin of Gurbantungut Desert

多枝柽柳作为干旱荒漠区重要的防风固沙灌木,其长期与风沙作用过程中形成了柽柳灌丛沙堆,在维持区域生态环境稳定及遏制沙漠蔓延方面发挥着重要作用。以古尔班通古特沙漠西南缘地区不同发育阶段沙堆上生长的多枝柽柳(Tamarix ramosissima)为研究对象,以空间序列代替时间序列的方法模拟沙堆堆积发育过程,揭示多枝柽柳生理特征对沙堆不同堆积发育阶段的响应及适应机制。结果表明:(1)在沙堆堆积发育过程中,多枝柽柳叶片相对含水量(RWC)及自由水/束缚水(Vs/Va)均呈先上升后下降的变化,其中,在增长阶段沙堆上最高,衰退阶段沙堆上最低,水分饱和亏(WSD)则呈相反趋势;组织含水量(TWC)呈逐渐上升的变化,清晨水势(Ψ_(PD))及正午水势(Ψ_(MD))呈逐渐降低的变化。(2)在沙堆堆积发育过程中,多枝柽柳的光合有效辐射(PAR)、叶片温度(TL)、光合电子传递速率(ETR)以及调节性能量耗散[Y_((NPQ))]日变化均呈先上升后下降的变化,衰退阶段沙堆上多枝柽柳各参数的日均值最大;各发育阶段沙堆上多枝柽柳的非调节性能量耗散[Y_((NO))]日变化均呈先下降后上升的变化,实际光化学效率[Y_((II))]日变化均呈“N”型,且Y_((II))日均值大小依次为增长阶段沙堆(0.489)>稳定阶段沙堆(0.463)>雏形阶段沙堆(0.455)>衰退阶段沙堆(0.439)。(3)气温(TEMP)和PAR与叶片Y_((II))均呈显著负相关,与ETR均呈显著正相关;Y_((II))与ETR、Y_((NO))与Y_((NPQ))均呈现显著负相关;PAR、TEMP是影响不同堆积阶段沙堆上多枝柽柳生理特性的主要环境因子。综合分析表明,在沙堆堆积发育过程中,多枝柽柳可通过调节光合作用和水分利用之间的协同关系来响应微环境的变化,从而减少其脱水风险以实现最大程度资源利用。

Tamarix ramosissima is an important windbreak and sand⁃stabilizing shrub in desert areas.Tamarix cones are formed through the long⁃term interaction between Tamarix and aeolian sand,which play an important role in maintaining the stability of regional ecological environment and curbing the spread of desert.In this paper,we studied the response and adaptation mechanism of the physiological characteristics of T.ramosissima on different developmental stages of Tamarix cones in the southwest edge of Gurbantungut Desert.The results showed that:(1)During the accumulation of Tamarix cones,the relative water content(RWC)and free water/bound water(Vs/Va)of leaves first increased and then decreased.The highest value was found on the growth stage of Tamarix cones,while the lowest value was found on the decline stage of Tamarix cones.However,the water saturation deficit(WSD)showed an opposite trend.The tissue water content(TWC)increased gradually,and the predawn water potential(Ψ_(PD))and midday water potential(Ψ_(MD))decreased gradually with the accumulation of Tamarix cones.(2)During the accumulation of Tamarix cones,the diurnal variations of photosynthetic active radiation(PAR),leaf temperature(TL),photosynthetic electron transfer rate(ETR)and adjusting energy dissipation quantum yield[Y_((NPQ))]of leaves increased first and then decreased,and the daily average values of these parameters reached the maximum in the decline stage of Tamarix cones.The diurnal variation of non⁃adjusting energy dissipation quantum yield[Y_((NO))]of leaves decreased first and then increased in different developmental stages of Tamarix cones.The diurnal variation of the actual photochemical efficiency[Y_((II))]was all of“N”type,and the daily average value of Y_((II))was in the order of growth stage cone(0.489)>stable stage cone(0.463)>embryonic stage cone(0.455)>decline stage cone(0.439).(3)The temperature(TEMP)and PAR were negatively correlated with Y_((II))and positively correlated with ETR.Y_((II))was negatively correlated with ETR,Y_((NO))and Y_((NPQ)).PAR and TEMP were the main environmental factors affecting the physiological characteristics of T.ramosissima during the development of Tamarix cones.The comprehensive analysis showed that T.ramosissima could respond to changes in the micro⁃environment by adjusting the synergistic relationship between photosynthesis and water use during the accumulation of Tamarix cones,thereby reducing the risk of dehydration and maximizing resource utilization.