Abstract
Bioclimate signifies the continuous interplay between plants and climate factors (primarily drought) and has a direct impact on the water relations and the duration of the rehydration process in water stressed plants. To explore the association between bioclimate and water physiology of forage species in semi-arid Mediterranean grasslands, we determined the seasonal variation in leaf water potential, turgid weight and relative water content in wild growing Dactylis glomerata L., Bromus inermis Leyss (perennial) and Bromus sterilis L. (annual) during the growing season. The study was conducted at the farm of the Aristotle University of Thessaloniki. The results of the current study reveal that B. sterilis maintained high levels of water potential most probably by accelerating its biological cycle and decreasing water content because it fails to sustain turgidity. Dactylis glomerata and B. inermis presented even higher water contents than B. sterilis for the same water potential. Dactylis glomerata exhibited substantially higher water potential and content than B. inermis by keeping the rehydration duration stable. The extensive creeping rhizome seems to allow B. inermis to sustain high values of water potential and content possibly ensuring turgidity. Regardless of the grass species the duration of rehydration ranged from 2.5 to 3.5 hours throughout the growing season. Our findings demonstrate that (a) D. glomerata and B. inermis are better adapted to Mediterranean semiarid conditions than B. sterilis and (b) turgid weight in Mediterranean forage species can safely be determined after a rehydration period of 3.5 hours.
Highlights
Water in a natural vegetation is directly associated with environmental factors, especially climate (Trejo et al, 2011)
Ψ followed a declining trend in all species during the growing season, which for D. glomerata and B. inermis was facilitated by the negative correlation between Vapor Pressure Deficit (VPD) and Ψ (r= 0.524, p ≤ 0.05 and r= -0.823, p ≤ 0.01 respectively)
The effect of elevated VPD on the water status of the three species studied was confirmed by the seasonal changes in both leaf water potential (Ψ) (Fig. 3) and relative water content (RWC) (Fig. 4)
Summary
Water in a natural vegetation is directly associated with environmental factors, especially climate (Trejo et al, 2011). One of the most important climatic factors affecting plant viability is the annual amount and especially the annual distribution of precipitation This is due to the physical and chemical properties of water, which render it essential for all physiological processes taking place in plants (Lambers et al, 2008). Plants address severe xerothermic periods by employing certain adaptive mechanisms, which ensure survival by avoiding and/or tolerating drought (Karatassiou et al, 2009; Kostopoulou et al, 2010) These mechanisms include the development of both short-term and long-term adjustments in plant organisms, such as the emergence of specific phenotypic characteristics, and changes in anatomy and morphology, as well as physiology (Lambers et al, 2008; Hayano-Kanashiro et al, 2009; Blum, 2011).
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