Academic journal article Global Media Journal

Halophyte Adaptation to the Gradient of Conditions at the Intertidal Zone of the White Sea Cost (with Triglochin Maritima L. as an Example)

Academic journal article Global Media Journal

Halophyte Adaptation to the Gradient of Conditions at the Intertidal Zone of the White Sea Cost (with Triglochin Maritima L. as an Example)

Article excerpt

Introduction

Triglochin maritima is a member of Juncaginaceae family. This species is dominating at the saline types of habitats (maritime and continental) in the boreal region of North hemisphere. The majority of works are devoted to the analysis of the geographic distribution of T. maritima and investigation of ecological conditions of its vegetation in plant communities with different ecology [1]. This dominant species has the wide ecological range and takes different ecological niches at the west coast of the White Sea throughout littoral and supralittoral from coastline to valley side [2]. It propagates with seeds and vegetatively [3].

The habitat conditions of higher vascular plants in the intertidal zone are complicated due to its high level of substrate-relief heterogeneity and variability of ecological factors [4]. The main process defining the instability of ecological conditions is the cyclical nature of tides, which change the habitat conditions of plants twice a day. This periodicity leads to the appearance of stress situations [5]. First of all, this is the exchange of groundair environment to water one, that results in fast (minutes) and sharp decrease of illumination (at the depth of 1 meter only about 20% remains); the decrease of oxygen and carbon dioxide content [6] and the disturbance of water regime [7,8]. In water environment HC03 prevails, which cannot be assimilated by terrestrial plants, and CO2 concentration is lower and the low diffusion rate decreases its availability for plants. In water, the boundary layer at the leaf surface which operates only under conditions of stagnation or slow motion of water flow increases [9]. The extent of flooding (partial or complete) and its duration (hours) depend on plant position on the littoral territory. During the low tide, when plants are completely exempt from water (hours), they are subjected to intensive illumination and can experience water deficiency. Every organism must be adapted to unstable ecological conditions during tidal cycle twice a day. It should be noted that all higher plant species inhabiting the littoral successfully undergo complete ontogenesis, which suggests that they managed to adapt to these unstable stress conditions. In literature, there are numerous works connected with the investigation of mechanisms of salt tolerance of halophytes [10,11], which grow under different salinity conditions, but the role of periodicity in the interaction of factors and their joint influence on the growth and development of higher plants are factually not investigated. It should be added that these phenomena are difficult for studying, and fleld researches are necessary in addition to cameral experiments.

The comparative investigation of structural and function leaf features of T. maritima growing in the gradient of conditions on coastal littoral of the Pomorsky coast of the White Sea was included in the objective of this study.

Views on Triglochin maritima

The object of investigation. Triglochin maritima L., Juncaginaceae family, is a perennial herbaceous plant with erected stems 1018 cm in height. The leaves are radical, narrowly linear, semicylindrical up to 60 cm in length. The rhizome is horizontal or oblique, short, strong. The inflorescence is racemose, manyflowered; the flowers are inconspicuous, greenish; the tepals are reddish on top; the fruits are ovate and consist of six fruitlets. The plant grows on the littoral of sea coasts, on wet salt-marsh meadows, peat bogs and shores of salt lakes. It is plyurizonalny species and has circumboreal areal. It can be met ubiquitously at the White Sea coast; it is the dominant and co-dominant in communities at zone of daily salt sea waters flooding. Also, T. maritima can grow and be dominant in regions higher than the daily flooding zone (especially in lowlands with clay substrate, where the sea water can stagnate since spring flooding) [2]. In coenopopulation, rather big groups with high value of dead central part of maternal individual are observed. …

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