1. 1. Introduction
บทนำแสงแดดที่พื้นผิวของโลกประกอบด้วยรังสียูวี-B (280- Sunlight at the earth’s surface, consisting of UV-B radiation (280–
315 นาโนเมตร), UV-A รังสี (315-400 นาโนเมตร), 315 nm), UV-A radiation (315–400 nm), photosynthetically active
ปราดเปรียวสังเคราะห์รังสี(PAR, 400-700 นาโนเมตร) และรังสีอินฟราเรด (> 700 นาโนเมตร) เป็นปัจจัยสำคัญเพื่อความอยู่รอดของสาหร่ายอัลไพน์สูงซึ่งจะสัมผัสนอกจากนี้ให้เข้ากับสภาพแวดล้อมที่รุนแรงเช่นอุณหภูมิการเปลี่ยนแปลงสภาพอากาศที่รุนแรงและพืชผักในระยะสั้นระยะเวลา[1] ในฐานะที่เป็น Blumthaler et al, มีรายงานก่อนหน้านี้การเปิดรับการเพิ่มขึ้นของการฉายรังสีที่เป็นอันตรายอย่างมากกับระดับความสูงภายใต้เงื่อนไขที่ฟ้าใส[2] radiation (PAR, 400–700 nm) and infrared radiation (>700 nm), is
an important factor for the survival of high alpine algae, which are
additionally exposed to harsh abiotic conditions such as temperature
changes, extreme weather conditions and short vegetation
periods [1]. As Blumthaler et al. have reported previously, the exposure
to harmful irradiation increases dramatically with altitude
under clear sky conditions [2]. Per 1000 mthey measured 9% higher
UV-A levels and an increased UV-B radiation by 18%.
Furthermore, environmental pollution primarily due to the use
of chlorofluorocarbons has promoted depletion of the stratospheric
ozone layer, which resulted in higher harmful short wave UV-B
irradiation on the earth’s surface. Although these compounds were
banned in the Montreal Protocol almost three decades ago, the
problem persists possibly due to rising concentrations of greenhouse
gasses [3]. Adaptation strategies are therefore required for
any living organism and they have extensively been studied for
higher plants [4,5]. In algae and cyanobacteria several adaptation
mechanisms to ultraviolet stress are known [6,7], for example
self-shading by mat formation [8], migration to higher water depth
(lower UV-levels) [9], the development of anti-oxidative systems
involving enzymatic and non-enzymatic strategies [10], or the synthesis
of special secondary metabolites including mycosporine-like
amino acids [11,12], scytonemin [13,14] and pigments [15,16]. The
latter are the best studied components and we also observed a rise
in pigment levels after UV exposure. Yet, very little is known for
algae and cyanobacteria from high mountain habitat, especially
concerning alteration in primary metabolites. In our study we
investigated the effects of elevated UV radiation on four respective
species, Pseudomuriella engadiensis, Coelastrella terrestris, Calothrix
sp. and Leptolyngbya foveolarum from high mountain habitat. The
most significant changes were noticed concerning highly polar
compounds, which showed to be nucleosides and aromatic amino
acids. Till date only a few analytical studies described the determination
of nucleosides in medicinal plants [17,18]. However, to the
best of our knowledge this study is the first report on the quantification
of these metabolites in algae and cyanobacteria.
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