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The aim of this study was to describe endophytic fungal communities residing in five mangrove species (Sonneratia caseolaris, Sonneratia hainanensis, Sonneratia ovata, Sonneratia Paracaseolaris, Sonneratia apetala) collected at the south coast of China. The colonization frequency (CF) of endophytes in roots, stems and leaves was measured and the structures of endophytic communities were investigated, using endophytic fungal diversity indices and similarity coefficients. We found high biodiversity and tissue specificity of endophytic fungi. A total of 391 fungal isolates were identified using morphological and molecular methods. We recovered a total of 39 distinct endophytic species, of which Cytospora, Diaporthe, Fusarium, Glomerella, Mycosphaerella, Phoma, Phomopsis and Stemphylium were the dominant fungal taxa. Most recovered species were found on more than one host species but the dominant species differed according to host and tissue type.

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In this paper, the dynamic anti-plane crack problem of two dissimilar homogeneous piezoelectric materials bonded through a functionally graded interfacial region is considered. Integral transforms are employed to reduce the problem to Cauchy singular integral equations. Numerical results illustrate the effect of the loading combination parameter k, material property distribution and crack configuration on the dynamic stress and electric displacement intensity factors. It is found that the presence of the dynamic electric field could impede of enhance the crack propagation depending on the time elapsed and the direction of applied electric impact. IntroductionDue to their intrinsic coupling between mechanical deformation and electric fields, piezoelectric materials are widely used as sensors and actuators to monitor and control the dynamic behavior of intelligent structural systems. Conventional piezoelectric devices are homogeneous or multi-layered, and they are susceptible to cracking and debonding due to uneven stress distributions or metal-to-ceramic bonds at which stress concentration occurs. In order to improve the integrity and reliability of piezoelectric devices, considerable research has been directed toward the development of functionally graded piezoelectric materials (FGPMs), [1][2][3]. In FGPMs, the material properties are continuously varied in one or more directions in order to eliminate mismatch of material properties at the interface and, thus, enhance the bonding strength and significantly improve the fracture toughness.Piezoelectric components are often subjected to impact mechanical and electrical loads in operation. Furthermore, in comparison with static loads, dynamic loads are likely to produce higher stress and electric fields in piezoelectric devices. It is of great importance to investigate the transient response of cracked piezoelectric materials and structures, therefore many studies investigated the fracture behavior of conventional piezoelectric materials and structures. The dynamic crack problem in a piezoelectric strip subjected to electro-mechanical impact was considered in [4], [5] and [6], while [7] analyzed a cracked piezoelectric laminate subjected to electromechanical impact loads. Paper [8] analyzed the interface crack between two piezoelectric layers under mechanical and electrical impacts, whereas [9] analyzed the interface crack of bonded piezoelectric and elastic half-space under transient electromechanical loads. Transient response of a smart laminate was investigated in [10] in which two piezoelectric layers were bonded to an elastic layer. In [11], the mode III Yoffe-type moving crack in a FGPM strip was considered, while in [12] a transient mode I crack in a FGPM plate, was investigated.

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