Abstract
Problem Statement and Objectives
Understanding the anatomical characteristics of wood in plant species, especially trees, is considered one of the most fundamental steps in plant sciences and ecology. Plant anatomy not only reveals the internal structure and the organization of different tissues, but also reflects their biological functions and adaptations to environmental factors and climatic changes [1, 2, 3]. Mangrove forests in southern Iran are of great economic, social, and ecological importance; however, human pressures and climate change pose a serious threat to the sustainability and functioning of these habitats [4]. In fact, comprehensive knowledge of the wood anatomy of plant species provides the necessary scientific basis for a better understanding of their growth patterns, development, and physiological responses to environmental stresses [5, 6]. Since the wood structure of trees, particularly the vessels and tissues associated with water transport, is directly influenced by environmental conditions such as salinity, temperature, and drought, examining these structures can contribute to identifying the impacts of climatic and human-induced changes at the ecosystem level [3, 7]. Given the limited knowledge of mangrove forests in southern Iran and the increasing pressures they face from climate change and anthropogenic activities, understanding their anatomical features is of vital importance. In this study, we provide anatomical insights into two mangrove species, Avicennia marina and Rhizophora mucronata, with an evaluation of vessel parameters in R. mucronata. We aimed to compare their wood anatomical characteristics and to suggest if they have potential for future dendrochronological studies.
Materials and Methods
Sampling from both species was carried out in natural and planted stands of selected sites. From each tree, a disk was taken from the stem section, and after preliminary preparation, radial sections were made. The sections were stained appropriately and microscopic slides were prepared for observation. Microscopic examinations were performed using a light microscope, and the obtained images were used for measurement and data recording. In this study, indices such as vessel diameter, vessel density, vessel area and vessel coverage were evaluated. The data were extracted and analyzed both quantitatively and qualitatively for comparison of the wood anatomy of both species.
Results
In Rhizophora mucronata, annual growth rings were clearly observable, but the boundaries of these rings were indistinct due to the gradual changes in vessel density, which followed a relatively regular pattern. Scalariform perforation plates and tyloses were observed inside the vessels. Regarding microscopic examinations in Avicennia marina, successive cambium was shown as the cambial bands may develop as single bands or are divided into two bands which means that those layers that are not entirely circular—being closed on both sides in certain cases, while others remain open on one side and appear incomplete. This phenomenon causes the heterogeneous pattern of growth layers on the disc surface; Growth layers and their boundaries were distinctly observable; however, annual growth rings were not distinguishable. In A. marina samples, vessel distribution was relatively irregular, tylosis formation and scalariform perforation plates were not recorded.
Conclusion
The findings of this study demonstrated that the two examined species exhibit considerable differences in wood anatomical features, which affect their potential in dendrochronological studies as well as their adaptability to environmental conditions. R. mucronata, with its regular growth rings and its high vessel density, shows greater potential for use in dendrochronology and the analysis of annual variations. In contrast, A. marina, with its irregular growth patterns, more strongly reflects strategies of adaptation to stressful and variable environments. These results can serve as a basis for further research in the field of ecology and the sustainable management of mangrove forests.