干旱和遮阴对荩草构件形态及生物量分配的影响

以具边坡草坪开发潜力的野生荩草(Arthraxon hispidus)为材料,设干旱[饱和持水量的81.75%(水分充足,W_0)、65.18%(轻度干旱,W_1)、43.64%(中度干旱,W_2)和27.88%(重度干旱,W_3)]和遮阴(0,10%,30%,50%,70%)及交互组合分析干旱和遮阴对荩草构件形态、生物量积累和分配的影响。结果表明,干旱、遮阴、干旱和遮阴协同处理对荩草构件形态有显著影响(P0.05),干旱对根的影响大于茎叶,遮阴对茎和叶影响大于根,协同处理对叶影响大于根和茎;W_2或W_3处理下单株叶数、叶长、叶宽、节间长和分枝数显著降低(P0.05),根长显著增加而单株气生根数显著减少;≥10%遮阴降低单株叶数、单株总节数、根长和单株气生根数,但株高显著增加,W_1×70%遮阴交互处理时单株叶数下降了66.94%,株高和节间长增加了86.11%和46.17%,W_3×70%遮阴交互处理时单株总节数和一级分枝数下降了62.43%和76.47%,根数下降了54.55%,且无气生根。干旱、遮阴、干旱和遮阴互作对生物量积累和分配有显著影响(P0.05),W_2和W_3干旱胁迫显著降低了单株和茎叶生物量及分配比,增加根生物量及根冠比应对中轻度干旱,W_3下单株及构件生物量下降约50%,而增加茎分配比以逃离重度干旱生境。≥30%遮阴显著增加叶生物量及分配比而降低根生物量及分配比,50%遮阴时根分配比及根冠比降低了81.48%和86.79%。干旱和遮阴协同处理可抵消或延缓干旱或遮阴造成的生长失衡,W_2×50%遮阴下荩草的生物量累积和分配与W_0×0遮阴相近。荩草可通过改变构件数量和质量性状及生物量分配,调整生长策略以应对干旱和遮阴胁迫,干旱和遮阴的协同影响,提高了荩草的抗逆性和生境适应能力。

Synergistic effects of drought and shade on component morphology and biomass allocation of Arthraxon hispidus

In this study, we examined the effects of drought and shade on wild Arthraxon hispidus.We set up 20 treatments using interactive combinations with five shade gradients (0, 10%, 30%, 50%, and 70%) and four drought gradients [81.75% (W0), 65.18% (W1), 43.64% (W2) and 27.88% (W3) of saturation moisture content].The purpose was to analyze the synergistic effect of shade and drought on component form and biomass accumulation and allocation of A.hispidus.The results showed that shade, drought and their interaction all had significant effects on component form(P<0.05).Drought had greater effects on roots than on stems and leaves, but shade had the opposite effect.Their interaction had greater effects on leaves than on roots and stems.Under the condition of moderate or severe drought (W2 or W3), leaf traits, internode lengths and number of branches was significantly reduced (P<0.05).Root length significantly increased but the number of aerial roots decreased.Shade ≥10% decreased leaf number per plant, number of nodes, root length and the number of aerial roots but plant height increased.The interactive effect of W1×70% shade decreased leaf number by 66.94%, and increased plant height and internodes length by 86.11% and 46.17%.The interactive effect of W3×70% shade decreased node number, primary branch number and root number by 62.43%, 76.47% and 54.55%, respectively;no aerial roots were found.Shade, drought and their interaction all had significant effects on biomass accumulation and allocation (P<0.05).Drought significantly reduced biomass per plant, stem and leaf biomass and allocation ratio of biomass.Under W3, biomass per plant and component biomass all decreased by about 50%, in which stem biomass increased to escape from severe drought.Shade ≥30% significantly increased leaf biomass but decreased root biomass.Under the condition of 50% shade, the distribution ratios of root and root∶shoot decreased by 81.48% and 86.79%, respectively.The interactive effect of drought and shade could offset or delay unbalanced growth caused by drought or shade.A.hispidus might adjust growth strategies by changing the quantity and quality traits of components and biomass allocation under drought or shade conditions.The synergistic effect of drought and shade enhanced resistance and adaptability of A.hispidus.