遮阴和干旱对荩草光合特性影响的协同作用

Synergistic effects of shade and drought on the photosynthetic characteristics of Arthraxon hispidus

为明确遮阴和干旱协同处理对荩草光合作用的影响,揭示荩草对遮阴和干旱胁迫的抗逆潜力和生态学特点。以具有边坡草坪开发价值的野生荩草为材料,设置5个遮阴梯度和4个干旱梯度交互形成的20个协同处理,对其进行叶生物量分配比、光合色素含量、光响应能力及光合参数的测定。结果表明,荩草叶面积、叶数、叶生物量和叶分配比均显著受遮阴、干旱、遮阴和干旱协同作用的影响(P<0.05),遮阴和干旱对叶面积、生物量和分配比有极显著协同作用(P<0.01),作用大小为分配比>叶数>叶面积>叶生物量;荩草的Chla、Chlb和Chla+b含量及Chla/b显著受遮阴、干旱、遮阴和干旱协同作用影响(P<0.05),Chlb比Chla易受生境影响,遮阴是影响叶绿素含量和比例的主要因子,干旱次之,遮阴和干旱对Chlb和Chla+b含量及Chla/b有显著协同作用(P<0.05);荩草光响应能力极显著的受遮阴、干旱、遮阴和干旱协同作用的影响(P<0.01),遮阴和干旱对光饱和点(LSP)、光补偿点(LCP)和最大净光合速率(Pnmax)有显著的协同作用(P<0.05),作用大小为Pnmax>LSP>LCP;荩草的光合速率(Pn)、蒸腾速率(Tr)、胞间CO2浓度(Ci)、气孔导度(Gs)均显著受遮阴、干旱、遮阴和干旱协同作用影响(P<0.05),遮阴和干旱对光合参数有极显著协同作用(P<0.01),遮阴主要影响Pn,干旱主要影响Gs、Ci和Tr,协同作用对Tr的影响最大,≤30%遮阴可缓解干旱引起的Pn、Tr、Ci、Gs下降程度,>30%遮阴则加重了下降趋势。遮阴和干旱协同作用比遮阴或干旱单一胁迫,提高了荩草光合叶面积和叶绿素含量,改变了光响应能力和光合参数,可提升荩草的抗逆潜力和生态适应范围。

The objective of this s tu d y w a s to c la r ify th e s y n e rg is t ic effects of shade and d ro u ght on th e p h o to syn -thetic characteristics of Arthraxon hispidus and to explore the re s is tan c e and ecological ch a ra c te r is t ic s of th is plant under shade and drought s t r e s s . Wi ld A . h isp idu s , a p lan t w ith p o ten tia l use in sloping law n develop-ment ,was subjected to d if fe ren t 20 t r e a tme n t s , combining five sh adin g in ten s it ie s （〇,1 0 % , 3 0 % , 5 0 % , 70%） and four drought int ensi t ies ; su f f ic ien t m o is tu re （W〇 ）,m ild d ro u ght （W／ ）,moderate dro ught （W2）, and severe drought （W 3）. Af te r 36 d a y s of t r e a tme n t, the le a f biomass a lloc a tio n r a t io , p h o to syn th e t ic p ig -ment content, l ight response abi l i t y , and p h o to syn th e t ic p a ram e te rs w e re d e te rm in ed . Th e ex ten t of shade anddrought and the synergy between shade and drought significantly affected the area, number, biomass, and allo-cation ratio of A . hispidus leaves （P 〈0. 05）. Shade and drought had a strong synergistic effect on leaf area, number, biomass, and biomass allocation ratio （P 〈0. 01）, with the strongest effect on the allocation ratio, followed by leaf number,leaf area, and then leaf biomass. Shade, drought, and the synergy between shade and drought also significantly affected the contents of chlorophyll a （Chla）,chlorophyll b （Chib）,Chla＋ b,and Chla/b （P 〈0. 05）. The Chib content was more sensitive to habitat than was Chla content. Compared with drought, shade had stronger effects on chlorophyll content and photosynthetic rate. Shade and drought had sig-nificant synergistic effects on Chib, Chla ＋ b , and Chla/b （P 〈0. 05）. Shade, drought, and the synergy be-tween shade and drought had highly significant effects on the light response capability （P 〈0. 01）. Shade and drought had significant synergistic effects on the light saturation point （L S P ） ,light compensation point （LCP）,and maximum net photosynthetic rate （_Pnmax） ,with the strongest effect on _Pn max followed by LSP and then LCP. Shade, drought, and the synergy between shade and drought significantly affected the photo-synthetic rate （P n） , transpiration rate （Tr） , intercellular C0 2 concentration （Ci）, and stomatal velocity （Gs） （P〈0 . 0 5）. Shade and drought had a strong and significant synergistic effect on photosynthetic parameters（P 〈0. 01）. Shade mainly affected Pn , drought main affected Gs, C;, and Tr , and their synergy mainly affected Tr. Shade of 30% or less reduced the size of the decrease in P n , Tr , C;, and Gs caused by drought, but shade of more than 30% exacerbated these decreases. Compared to each single stress, the synergistic effect of shade and drought increased the photosynthetic leaf area and chlorophyll content and altered the light response ability and photosynthetic parameters of A . hispidus. These changes contributed to the stress resistance and ecologi-cal adaptation of A . hispidus.