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The effect of light on seed germinationWhat is Transpiration?

How does light intensity and duration affect the rate of photosynthesis?

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Effect of different colors of light on the rate of photosynthesis.

The first observation concerns mountain beech (Nothofagus solandri). This is a dominant canopy tree in subalpine forests of New Zealand, and patterns of seedling regeneration around isolated trees on the Waimakariri floodplain are highly characteristic. While 95% of young seedlings occur beneath the canopy of a parent tree, they are not distributed randomly. Rather, they tend to cluster on the western side, and 65% occur in a narrow sector between 165°S and 285°S (Figure 2). Wind effects on seed dispersal are not responsible because prevailing winds blow in the opposite direction; however, seedlings on the south to western sides of parent trees are protected from direct sunlight all day throughout winter, and from morning sun in spring and early summer.

Investigate the effect of light on seed germination.

Lieth, J.H. and C.C. Pasian. 1990. A model forphotosynthesis of rose leaves as a function of photosynthtically activeradiation, leaf temperature, and leaf age. J. Amer. Soc. Hort. Sci. 115: 486-491.

Effects of different colors of light on the photosynthesis rate.

Plants have an optimum temperature for photosynthesis, which varies.

At high temperatures dry matter production is often more limited by photosynthesis than by cell expansion (while at low temperatures dry matter production is more limited by cell expansion than by photosynthesis). Generally, the inhibition of photosynthesis and other growth maintaining processes during moderate or short-term heat stress results in a comparatively small reduction in the rate of dry matter production (relative growth rate) (Chapter 6.2.2; ). As temperature increases within a plant’s thermal range, the duration of growth decreases but the rate of growth increases, as shown earlier in this chapter. As a consequence, organ size at maturity may change very little in response to temperature, despite variation in growth rate. As temperatures are raised further, an increased rate of growth is no longer able to compensate for a reduction in the duration of development, and the final mass of any given organ at maturity is reduced. This response can be seen in a range of tissues including leaves, stems and fruit. A smaller organ size at maturity due to high temperature is associated with smaller cells rather than a change in cell number. This implies that cell enlargement is more sensitive to temperature than is cell division. The reduced duration of development can also limit the number of organs that are produced, e.g. grain number in wheat is reduced when plants are grown at moderately high temperatures (Stone and Nicolas 1994). Under certain conditions plants grown under moderate heat stress accumulate sugars in their leaves, indicating that translocation can be more limiting than photosynthesis, but this is not thought to be a general limitation.

For many years, the inhibition of gross photosynthesis was thought to occur at temperatures too low to be explained by the thermal deactivation of photosynthetic enzymes. Experiments comparing the thermal response of many steps in the photosynthetic apparatus, suggested the initial inhibition was due to the sensitivity of the thylakoid membrane to high temperatures (Berry and Bjorkman 1980). However, this view has been questioned recently with the observation that at moderately high temperatures photosynthetic inhibition coincides with a reversible reduction in the activity of certain Calvin cycle enzymes (Sharkey 2005). Severe heat stress is still thought to be due to injury of PSII, through direct cleavage of the D1 protein and a range of other mechanisms. Although the thermal sensitivity of PSII is not solely due to the thermal sensitivity of cell membranes, membrane properties are a major regulator of both inhibition and injury of PSII (Sharkey 2005; Allakhverdiev et al. 2008).

# leaves floating Time (min) Effect of Temperature on Photosynthesis

Using this data to analyze our question, temperature does indeed affect the rate of photosynthesis.

Within minutes of temperature rising above the optimum, the expression of most genes used for general metabolism is inhibited, however, a sub-set of specialised stress response genes are actively up-regulated. The best characterised of these genes are a multi-family group known as heat shock proteins (HSP). HSP occur in all organisms. In plants, they show differential expression in many tissues and many cell compartments. HSP utilise a novel transcription factor to respond directly to heat, and their levels have been shown to rise along with temperature until the lethal threshold temperature is reached. On exposure to high temperature HSP expression typically peaks after 1-2 hours and diminishes after 6-8 hours, after which the cell environment is modified enough for the transcription and translation of other genes to resume (Larkindale et al. 2005; Allakhverdiev et al. 2008).

Figure 14.28. In heat tolerant plants, growth at warm temperatures results in acclimation of photosynthesis. Adjustments in membrane composition, protein synthesis, and metabolic regulation alleviate some of the effects of high temperature. Acclimation is mediated, in part, by an increase in expression of heat shock proteins. Based on Sage and Kubien (2007) and Yamori et al. (2014).

however, upon further research, we learned that plants have an optimum temperaturefor photosynthesis,which is about 25degreescelsius.
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  • The effect of temperature on photosynthesis - SlideShare

    Based on our data and research, we can determine that temperature affects the rate of photosynthesis in plants.

  • The effect of temperature on photosynthesis 1

    So, again, the e higher or lower the temperature as compared to the optimum, the lower the rate of photosynthesis.

  • Experiment to Investigate the Effect of Temperature on …

    What is the effect of temperature on photosynthesis? - …

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How does temperature affect photosynthesis

Figure 14.13. Maize (a subtropical C4 species) has a high optimum temperature (~30 °C) for CO2 assimilation, while barley (a temperate C3 species) has a lower, but less distinct optimum (~15 °C). Doubling CO2 has little effect on CO2 assimilation rate by maize (not shown here), but greatly increases the absolute rate and optimum temperature for barley by suppressing photorespiration. This O2-dependent loss of carbon increases with temperature and is largely responsible for the low optimum temperature of photosynthesis in many C3 species. Based on Labate, Adcock and Leegood (1990) Planta 188, 547-544.

Temperature's Effect on Photosynthesis;

While net photosynthesis is the resulting balance between gross photosynthesis and respiration, low or even negative net photosynthetic rates can have a significant effect on productivity. An example of this would be photosynthesis by the green pod of many legumes where the net uptake of CO2 is low because of a high rate of pod and seed respiration. A rise in temperature will result in greater respiratory losses from the pod and a reduction in net uptake of CO2, but this does not diminish the importance of pod photosynthesis.

Science Experiments on Environmental Education and Biology

A combination of at least two factors may be associated with the failure of C3 species to respond more favourably to high temperature in terms of CO2 assimilation. One is the limit placed on photosynthesis by ambient CO2 (Figure 14.13), and a second is the concurrent rise with increasing temperature of light-stimulated photorespiration, which is effectively absent from C4 species. Increased atmospheric CO2 inhibits photo-respiration and results in a much greater uptake of CO2 in response to increased temperature in C3 species.

The Effect of Photosynthesis and Respiration on the ..

Some C3 species such as snow tussocks have an optimum temperature for CO2 assimilation as low as 5°C, but it is important to note that absolute rates at this temperature may be relatively low (Figure 14.12). Most temperate grasses and cereals as well as many woody species have temperature optima in the range from 15°C to 25°C and within this range many C3 species show only small changes in CO2 uptake. In contrast to temperate C3 species, CO2 assimilation by C4 species increases considerably with a rise in temperature from 15°C to 30°C and optimum temperatures may be greater than this (Figure 14.12). Rice, a subtropical C3 species, has a higher temperature optimum for CO2 assimilation than temperate C3 species. Under high light, C4 species have a characteristically greater photosynthetic rate than the C3 species, but these differences disappear and may be reversed at low temperature. Growth temperatures may also influence the optimum temperature for net photosynthesis, which may therefore vary with season or location. However, modifications leading to an improvement in photosynthesis at high temperatures can result in decreased performance at low temperatures and vice versa.

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