5 results
23 - Photosynthesis during leaf development and ageing
- Edited by Jaume Flexas, Universitat de les Illes Balears, Palma de Mallorca, Francesco Loreto, Hipólito Medrano, Universitat de les Illes Balears, Palma de Mallorca
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- Terrestrial Photosynthesis in a Changing Environment
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- 05 March 2013
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- 19 July 2012, pp 353-372
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Summary
Introduction
Periods of leaf development and senescence comprise a significant fraction of leaf lifespan. Therefore, leaf lifetime carbon gain is importantly modified by the overall duration and time kinetics of these processes (Wilson et al., 2001; Morecroft et al., 2003; Grassi and Magnani, 2005). In addition, significant time-dependent changes occur in leaf function in mature non-senescent leaves owing to continuous accumulation of cell walls and concomitant reductions in mesophyll-diffusion conductance, as well as owing to re-acclimation of foliage to dynamically changing environmental conditions. Such modifications are of particular importance in evergreen species supporting foliage for several growing seasons, but foliage structure and physiological potentials also change in mature non-senescent leaves in deciduous species (Flexas et al., 2001; Wilson et al., 2001; Niinemets et al., 2004a).
A large body of information of fine-scale regulation of leaf development and senescence has become available (Dengler and Kang, 2001; Kessler and Sinha, 2004; Fleming, 2005; Lim et al., 2007). Although these studies cover in depth the regulatory sequences and signalling pathways during leaf development and senescence, the last comprehensive series of reviews on leaf photosynthetic modifications in developing leaves was published in 1985 (Shesták, 1985). Furthermore, the available treatises of leaf ontogenetic effects on photosynthesis have focused on herbaceous plants or on fast-growing deciduous trees. However, the rate of developmental and ageing processes largely differs among species with varying leaf longevity and structure (Miyazawa et al., 2003). Consideration of these functional-type specific variation patterns in leaf development is of major importance for prediction of plant photosynthetic productivity of highly structured natural plant communities consisting of species with varying leaf longevity and architectural constitution.
29 - Ecophysiology of photosynthesis in semi-arid environments
- Edited by Jaume Flexas, Universitat de les Illes Balears, Palma de Mallorca, Francesco Loreto, Hipólito Medrano, Universitat de les Illes Balears, Palma de Mallorca
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- Terrestrial Photosynthesis in a Changing Environment
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- 05 March 2013
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- 19 July 2012, pp 448-464
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Summary
Introduction
Arid and semi-arid environments currently cover a third of terrestrial Earth surface. By definition, ‘semi-arid’ refers to environments where insufficient water is available for vegetation growth. Semi-arid regions are characterised by being intermediates between desert (arid) and humid climates (Fig. 29.1), with an annual precipitation (250–1000 mm year–1) typically lower than the potential evapotranspiration (PET). Furthermore, precipitation is concentrated in specific periods of the year, inducing interruptions of the growing season when water availability reaches the threshold that dramatically limits ecosystem functioning. In addition to pronounced seasonality, a third component is the unpredictability of precipitation, resulting in short drought periods even during the humid season. This unpredictability also refers to high year-to-year variability, which increases with decreasing annual precipitation, often leading to alternation of dry and humid cycles lasting several years. The inter-annual variability is also mirrored in actual evapotranspiration (AET).
The availability of precipitation and the topography of the site are the major factors determining the amount of water available for plants. However, a more detailed division of semi-arid biomes should also consider other components of climate. Temperature is a major climatic element differentiating semi-arid ecosystems. Aside from water, low temperatures become a limiting factor for plant productivity and growth in the coolest semi-arid zones, whereas heat stress can limit plant production in savannas and Mediterranean environments. According to Köppen (1936) classical classification, major biomes in semi-arid climates are savannas (Aw according to Köppen), steppes (BS) and Mediterranean-type ecosystems (Cs). Oceanic and tropical influences prevent low temperatures in Mediterranean regions and especially in savannas. Steppes are characterised by continental influences with wide seasonal and daily ranges in temperature.
30 - Ecophysiology of photosynthesis in temperate forests
- Edited by Jaume Flexas, Universitat de les Illes Balears, Palma de Mallorca, Francesco Loreto, Hipólito Medrano, Universitat de les Illes Balears, Palma de Mallorca
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- Terrestrial Photosynthesis in a Changing Environment
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- 05 March 2013
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- 19 July 2012, pp 465-487
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Summary
The Temperate-Forest Environment
The temperate zone is characterised by pronounced seasonality with temperatures of the warmest month generally higher than 10°C and temperatures of the coldest month generally between –10 and 10°C (Köppen, 1936; Russell, 1931). Temperature is arguably the most important climatic variable in temperate forests. Temperatures during warm and cold periods are strongly variable within the temperate-forest biome, depending on continentality, latitude and topography (Fig. 30.1). Total precipitation is generally greater than 50–75 cm year–1 and is more uniformly distributed over the year than in arid (Chapter 28) and in semi-arid (including Mediterranean ecosystems) (Chapter 29) habitats. The annual input of solar radiation is between 2500–6000 MJ m–2, varying with site latitude, cloudiness and topography (Jarvis and Leverenz, 1983).
Temperate forests are dominated by deciduous trees in oceanic and continental areas of the Northern hemisphere, while evergreens dominate in warmer locations and in the Southern hemisphere. In the edges of temperate biome, mixed forest may appear. Thus, on the cold border the transition to steppes is characterised by open conifer or deciduous forests, while there are mixed conifer-deciduous woodlands in the transition to the boreal biome. In the warm border, the transition is characterised by subtropical evergreen forests in humid locations and by the presence of deciduous Mediterranean oaks in more arid sites.
16 - Photosynthetic responses to radiation
- Edited by Jaume Flexas, Universitat de les Illes Balears, Palma de Mallorca, Francesco Loreto, Hipólito Medrano, Universitat de les Illes Balears, Palma de Mallorca
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- Terrestrial Photosynthesis in a Changing Environment
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- 05 March 2013
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- 19 July 2012, pp 239-256
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Basic characteristics of solar radiation
Among the factors affecting plants, solar radiation is perhaps the most heterogeneous in space and time. Important parts of solar radiation provide energy for photosynthesis and serve as signals in photoregulation of plant growth and development. The sun radiates energy in the spectral range from 280 to 4000 nm, with a maximum in the blue-green (480 nm; Fig. 16.1). Within the PAR, solar radiation peaks at ca. 590 nm (Fig. 16.1). Solar radiation can be segregated into direct solar radiation and diffuse sky radiation, which reaches the ground after multiple scattering on atmospheric particles and clouds, reflection from the ground surface and additional scattering in the atmosphere (Ross, 1981).
The widespread, albeit vague, term light is used for the portion of the electromagnetic spectrum in the vicinity of visible light (Kohen et al., 1995). Many past ecological and physiological studies were based on measurements that represent the stimulation of the human eye by radiant energy, a measure called illuminance and expressed in foot-candles (English system) or luxes (metric system). The human eye is most sensitive in the green spectral region, centered around 550 nm, whereas any quanta in the spectral region of 400–700 nm have enough energy to drive photosynthesis, so illuminance is obviously not well suited for plant science.
26 - Whole-plant photosynthesis: potentials, limitations and physiological and structural controls
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- By Ü. Niinemets
- Edited by Jaume Flexas, Universitat de les Illes Balears, Palma de Mallorca, Francesco Loreto, Hipólito Medrano, Universitat de les Illes Balears, Palma de Mallorca
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- Terrestrial Photosynthesis in a Changing Environment
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- 05 March 2013
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- 19 July 2012, pp 399-423
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Summary
Introduction
Whole-plant photosynthesis is a complex process depending on photosynthetic activity of single leaves, plant architecture and plant biomass distribution between support and assimilative tissues. This chapter reviews the importance of whole-plant photosynthesis in ecology and plant science, the possible ways of estimating whole-plant carbon-gain rates and the determinants of whole-tree carbon gain. It further analyses the changes in whole-tree carbon gain in different environments and with plant aging and increasing size. The main message of this chapter is that whole-plant photosynthetic productivity is determined collectively by a series of physiological and structural traits, by within-canopy variation in environmental drivers and by foliage acclimation to the within-plant environmental heterogeneity. Therefore, whole-plant photosynthesis responds differently to the environment than does the sum of single-leaf photosynthetic responses.
Whole-plant photosynthesis: importance for large-scale carbon fluxes
Driven by the need to understand and predict global change, there is strong interest in determinants of vegetation carbon gain at higher scales ranging from whole plants to canopies, landscapes, biomes and globe (e.g., Williams et al., 2004; Ollinger et al., 2008; Duursma et al., 2009). There is a large variation in physiological activity among the leaves of the same plant owing to differences in leaf ontogenetic status, as well as owing to leaf acclimation to within-canopy light, temperature and humidity gradients. Because of this large variation among leaves, the whole-plant performance is difficult to assess from single-leaf measurements (Klingeman et al., 2000), and poor correspondence of single-leaf gas-exchange rates and plant growth has been observed in numerous studies (e.g., Lambers and Poorter, 1992; Lawlor, 1995).
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