In this work, photosystem II (PSII) photochemistry, leaf water potential, and pigment contents of male and female Pistacia lentiscus L. were investigated during a seasonal cycle at three different, arid locations: superior semiarid, inferior semiarid, and arid. The results showed that the gender, season, and the site conditions interacted to influence the quantum yield and pigment contents in P. lentiscus. Predawn leaf water status was determined only by the site and season. The annual patterns of PSII maximum quantum efficiency (Fv/Fm) were characterized by a suboptimal activity during the winter, especially, populations with the more negative water potential exhibited a lower chlorophyll (Chl) a content and chronic photoinhibition irrespective of a gender. We also demonstrated that both photochemical or nonphotochemical mechanisms were involved to avoid the photoinhibition and both of them depended on the season. This plasticity of photosynthetic machinery was accompanied by changes in carotenoids and Chl balance. In the spring, the female Fv/Fm ratio was significantly higher than in male individuals, when the sexual dimorphism occurred during the fruiting stage, regardless of site conditions. P. lentiscus sex-ratio in Mediterranean areas, where precipitations exceeded 500 mm, was potentially female-biased. Among the fluorescence parameters investigated, nonphotochemical quenching coefficient appeared as the most useful one and a correlation was found between Chl a content and Fv/Fm. These results suggest that functional ecology studies would be possible on a large scale through light reflectance analysis. and S. Ait Said ... [et al.].
The climatic variability and climate changes in the geological history of Earth are correlated with the environmental development. A special attention is paid to the impact of changing climate on the water resources and hydrological cycle. Possible impact of man's activities on the climatic variability is also discussed. Can the regulation of such activities slow down or bring to a stop the forthcoming climate change? A comparison of data from the Holocene period and from modern history indicates that the climatic variability and climate change have been always produced by external periodic phenomena and occasional cataclysmic events. In other words, the climate has never been stable and administrative measures limiting man's influence on the climate can bring only partial results. Considering that the climatic change is an unavoidable process, following measures should be taken: First, alternative scenarios of possible climatic development, would it be cooling or warming, should be set up. Second, preventive and protective methodologies need to be prepared for each scenario well in advance. Third, technologies facilitating man's survival and everyday life under changed climatic situation should be developed. and Klimatická variabilita a změny klimatu jsou sledovány v geologické historii Země a korelovány s historií životního prostředí. Zvláštní pozornost se věnuje vlivu měnícího se klimatu na vodní zdroje a hydrologický cyklus. Také je diskutován vliv činnosti člověka ve vztahu ke klimatu. Je možné redukcí takových aktivit zpomalit nebo zcela zastavit klimatické změny? Porovnání dat z holocénu a moderní historie ukazuje, že klimatická variabilita a změny byly vždycky vyvolávány mimozemskými periodickými vlivy, případně občasnými katastrofickými jevy. Jinými slovy, klima nikdy nebylo stabilní. Proto také administrativní opatření, omezující vliv člověka na klima, mohou být úspěšná pouze do jisté míry. Uvážíme-li, že klimatická variabilita i její hydrologické následky jsou nevyhnutelné, je třeba připravit příslušné scénáře možných klimatických změn, ať už souvisí s ochlazováním nebo oteplováním. Pro každý ze scénářů je třeba navrhnout metody preventivních a ochranných opatření s dostatečným předstihem. Konečně bude třeba vypracovat nové technologie usnadňující život člověka ve změněných klimatických podmínkách.