苜蓿叶片结构和光合特性对菌磷添加的响应

Leaf structure and photosynthetic properties of alfalfa in response to bacteria and phosphorus addition

探究菌磷互作对紫花苜蓿叶片解剖结构及光合特性的影响机制,明确紫花苜蓿叶片结构与光合参数之间的关系。采用双因素完全随机区组设计,接菌处理分别为单接种胶质芽孢杆菌(J_(1))、巨大芽孢杆菌(J_(2))、两种菌混合接种(J_(3))和不接种(J_(0)),施磷处理为施磷(P_(2)O_(5))100 mg·kg^(-1)(P_(1))和不施磷(P_(0))。通过对紫花苜蓿叶片光合参数和解剖结构指标进行测定,并使用回归分析明确叶片光合特性与解剖结构之间的关系。结果表明,在相同接菌条件下,紫花苜蓿叶片厚度、上表皮厚度、下表皮厚度、栅栏组织厚度、海绵组织厚度、导管直径、筛管直径、净光合速率日均值(P_(n))、蒸腾速率日均值(T_(r))、气孔导度日均值(G_(s))均为P_(1)处理大于P_(0)处理;叶绿素相对含量(SPAD值)均为P_(1)处理显著大于P_(0)处理(P<0.05);而胞间CO_(2)浓度(C_(i))日均值为P_(1)处理小于P_(0)处理。在相同施磷条件下,紫花苜蓿叶片厚度、上表皮厚度、下表皮厚度、栅栏组织厚度、海绵组织厚度、导管直径、筛管直径、P_(n)日均值、T_(r)日均值、G_(s)日均值、SPAD值均为施菌处理大于未施菌处理,且在J_(3)处理达到最大值;而C_(i)日均值为施菌处理小于未施菌处理。菌、磷对苜蓿叶片厚度、上表皮厚度、下表皮厚度、栅栏组织厚度、海绵组织厚度、导管直径有极显著的影响(P<0.01),菌磷互作对苜蓿叶片厚度及栅栏组织厚度有显著影响(P<0.05)。回归分析表明,P_(n)日均值与叶片厚度、导管直径、筛管直径、栅栏组织厚度、海绵组织厚度呈显著正相关(P<0.05),与栅海比呈显著负相关(P<0.05)。对紫花苜蓿叶片结构及光合特性进行综合性评价,由高到低为J_(3)P_(1)>J_(1)P_(1)>J_(2)P_(1)>J_(3)P_(0)>J_(0)P_(1)>J_(1)P_(0)>J_(2)P_(0)>J_(0)P_(0),即共同接种胶质芽孢杆菌和巨大芽孢杆菌,并施磷(P_(2)O_(5))100 mg·kg^(-1)时有利于促进紫花苜蓿叶片各组织的生长发育,进而促进紫花苜蓿叶片的光合进程。

In this study,we investigated the effects of bacteria-phosphorus interactions on the anatomical structure and photosynthetic properties of alfalfa(Medicago sativa)leaves,and explored the relationship between alfalfa leaf structure and photosynthetic parameters.A two-factor randomized block design was adopted,with single inoculation of Bacillus mucilaginosus(J_(1)),Bacillus megaterium(J_(2)),a mixture of both bacteria(J_(3)),and no bacteria(J_(0)),with phosphorus application(P2O5 at 100 mg·kg^(-1))(P_(1))or without phosphorus application(P_(0)).The leaf photosynthetic indexes and anatomical structure indexes were measured,and the relationship between leaf photosynthetic characteristics and anatomical structure was clarified using regression analyses.It was found that under the same bacterial inoculation conditions,the leaf thickness,upper epidermal thickness,lower epidermal thickness,palisade parenchyma thickness(PPT),spongy parenchyma thickness(SPT),vessel diameter and diameter of sieve tubes,and the daily mean values of net photosynthetic rate(P_(n)),transpiration rate(T_(r)),stomatal conductance(G_(s))of alfalfa leaves were higher in the P_(1) treatment than in the P_(0) treatment;the relative chlorophyll content(SPAD value)was significantly higher in the P_(1) treatment than in the P_(0) treatment(P<0.05);and the daily mean values of intercellular CO_(2) concentration(C_(i))were lower in the P_(1) treatment than in the P_(0) treatment.Under the same phosphorus application conditions,the leaf thickness,upper epidermal thickness,lower epidermal thickness,PPT,SPT,vessel diameter and diameter of sieve tubes,and daily mean values of P_(n),T_(r),G_(s),and SPAD of alfalfa leaves were higher in bacteria-inoculated treatments than in the uninoculated treatment,with maximum values in the J_(3) treatment.The daily mean value of C_(i) was lower in bacteria-inoculated treatments than in the uninoculated treatment.Bacteria and phosphorus had highly significant effects on alfalfa leaf thickness,upper epidermal thickness,lower epidermal thickness,PPT,SPT,and vessel diameter(P<0.01).Bacteria×phosphorus interactions were significant for alfalfa leaf thickness and palisade tissue thickness(P<0.05).The daily mean values of P_(n) were significantly and positively correlated with leaf thickness,vessel diameter,sieve tubes diameter,PPT,and SPT(P<0.05),and significantly negatively correlated with PPT∶SPT ratio(P<0.05).In a multivariate evaluation based on the structural and photosynthetic properties of alfalfa leaves,the treatments were ranked,from most to least conducive to leaf development and photosynthesis,as follows:J_(3)P_(1)>J_(1)P_(1)>J_(2)P_(1)>J_(3)P_(0)>J_(0)P_(1)>J_(1)P_(0)>J_(2)P_(0)>J_(0)P_(0).Therefore,a phosphorus application rate of 100 mg·kg^(-1) and double inoculation with B.mucilaginosus and B.megaterium was most conducive to the photosynthetic process of alfalfa leaves,with strong positive effects on growth and physiological development.