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عنوان فارسی مقاله:
زمان و گرما برای تولید مثل جنسی: مقایسه فنولوژی Chara hispida دو جامعه در عرض های جغرافیایی مختلف
عنوان انگلیسی مقاله:
Time and heat for sexual reproduction: comparing the phenology of Chara hispida of two populations at different latitudes
سال انتشار : 2017
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مقدمه انگلیسی مقاله:
1. Introduction
Phenology is the study of the seasonal timing of biological events. Organisms develop from one phenophase to another in their life cycle depending on their biology and “internal clock” (Resco et al., 2009). However, authors have also described how the initiation of phenological events is driven predominantly by climatic shifts associated with the change of seasons, rather than by intrinsic controls (Badeck et al., 2004). Unpredictability can affect the success of individuals and populations if it affects the precise timing of events −especially those regarding reproduction, such as flowering or fruiting in plants. Thus, organisms have to respond to environmental factors that are variable from year to year (Ausín et al., 2005). Factors related to light availability (such as photoperiod or irradiance), water availability (such as precipitation or hydrope-riod) and other climatic factors (such as temperature) act as cues for phenology, as they inform about short-term environmental trends and foreseeable future conditions (Pau et al., 2011). Hence, phenology is considered to be the simplest process which allows us to track the current changing climate and its effects on the ecology of both animal and plant species (Walther et al., 2002). All the environmental factors that affect phenology vary with the geographical factors in which the organisms are living (Pau et al., 2011), determining the distribution of species (Chuine, 2010). According to Hopkins’ Bioclimatic Law, a variation in geographical position − as defined by latitude, longitude and altitude − implies a constant variation in climatic conditions and phenology across temperate areas (Hopkins, 1918). So, with other conditions being equal, there is a progression of spring phenological events from south to north, from west to east and from lower to higher elevation. Hopkins research was focused on the phenology of insects, forest trees, wild shrubs, farm crops and cultivated plants from gardens, all of them being from terrestrial ecosystems. Research based on remote sensing techniques and vegetation indexes (Schwartz,1998; Pettorelli et al., 2005) delved deeper into the description of the spring phenology advance in terrestrial plants, the so called “green up”, through latitudinal gradients. For aquatic ecosystems, recent examples of the application of these methods exist (Hestir et al., 2015; Luo et al., 2016), but no information is available concerning the effect of latitude on the reproductive phenology of submerged aquatic plant species or the fulfilment of Hopkins’ Law. Among environmental factors, light and temperature especially affect phenology by directly influencing biochemical processes and the development rates of organisms (Franklin, 2009). To study the seasonality in environmental factors, curve fitting techniques have been applied, as they allow one to represent the annual pattern on a temporal axis and to characterize some key dates within the year that can be related to biological events. The onset, the maximum or the end ofthe growing season are some examples ofthese key dates (Pettorelli et al., 2005) that can be calculated based on temperature dynamic. Other methods can be used to explore phenological events, such as the broadly used growing degree day model, also called the thermal time model (Trudgill et al., 2005). It is based on the accumulation of heat above a base temperature, called the low threshold of temperature. This model assumes that each organism requires a particular heat sum to develop to the next phenophase in its life cycle, so when that required thermal summation is reached, the phenological event is triggered. There are many examples of the application of this model for terrestrial organisms, especially in plants (Zavalloni et al., 2006; Sacks and Kucharik, 2011; Kramer et al., 2012). However, its use for submerged macrophytes is scarce (Spencer et al., 2000; Spencer and Ksander, 2001), particularly for green macroalgae such as charophytes (Rey-Boissezon, 2014; Calero et al., 2015).
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کلمات کلیدی:
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