Dynamics of photosynthesis in fluctuating light.
Michael states that a higher light intensity would increase the rate of photosynthesis, however, Reona disagrees.
The photosynthesis 'light response curve' - Marietta …
Regardless of photosynthetic capacity, the ability of a plant to use sunflecks is also affected by the induction requirement of photosynthesis. When a leaf that has been in low light for some time is exposed to an increase in photon irradiance, the rate of photosynthesis does not increase instantaneously to the new level. Instead, there is a gradual increase in assimilation which can take from 10–60 min for completion. This ‘induction period’ varies according to species as well as the induction state of the leaf concerned. Three different processes are involved; namely (1) buildup of PCR cycle intermediates and in particular ribulose-1,5-bisphosphate (RuBP), (2) light-dependent activation of Rubisco, and (3) light-dependent opening of stomata. Each of these processes follows a different time-course. Buildup of a metabolite pool is fastest (1–2 min), followed by Rubisco activation (2–5min) and ﬁnally stomatal opening (up to 60 min). Relaxation in low light is more protracted but generally occurs in the same sequence, leading to a decline in the induction state.
Photosynthesis is the process by which plants convert light energy into chemical energy for use in growth and cellular repair. The ability of plants to capture light energy, carry out photosynthesis and grow is affected by many environmental factors including temperature, water and nutrient supply. Plants living in natural environments are also subject to competition and shading from other plants and have a number of biochemical and morphological adaptations to increase the efficiency of light absorption, whilst avoiding light stress. Various adaptations of photosynthesis exist that allow plants to tolerate extreme environmental conditions. Ultimately, the overall net photosynthetic rate of ecosystems has a major impact on the global carbon budget. These impacts may be significantly altered by global warming and subsequent climate change.
CO 2 assimilation, photosynthetic light response curves, ..
Modelling photosynthesis in fluctuating light with inclusion of stomatal conductance, biochemical activation and pools of key photosynthetic intermediates.
A dynamic model of photosynthesis in varying light taking account of stomatal conductance, C3-cycle intermediates, photorespiration and Rubisco activation.
Photosynthetic light response of the C4 grasses …
Light interception can also be regulated at a tissue and organelle level. Photosynthetic tissue can be concentrated equally on both sides of a leaf (isobilateral) to maximise light absorption from either side, or preferentially on one side (dorsiventral) as is common in species where leaves are predominantly horizontal.
Epidermal cells in some rainforest shade-adapted species are shaped to enhance light capture by acting as a lens. The optical properties of such cells focus incident sunlight into the layer of photosynthetic tissue just below the epidermis, reducing light lost due to reflectance and transmittance.
Photosynthetic light-response curves | SpringerLink
The light-dependent reactions of photosynthesis.
Profiles of C-14 fixation through spinach leaves in relation to light absorption and photosynthetic capacity.
Light dependent reaction for photosynthesis class 02 - …
An improved dynamic model of photosynthesis for estimation of carbon gain in sunfleck light regimes.
Photosynthesis: light dependent reaction - Duration: 8:09
Kinetic modeling of the light-dependent photosynthetic activity of the green microalga Chlorella vulgaris.
The Photosynthesis-Light Response Curve (PDF …
There are also differences in chloroplast structure between plants grown in low light and high light. Shade chloroplasts tend to be larger than those found in sun plants. They also contain more thylakoid membranes which show higher levels of randomly arranged granal stacking into appressed regions, as shown by the extreme development of grana in Figure 12.6. The higher proportion of appressed to non-appressed membranes found in shade chloroplasts is the result of increased photosynthetic system II (PSII) and antenna (LHCII) content. LHCII is thought to be involved in thylakoid appression and formation of granal stacks. Plants grown in low light also tend to have lower Chl a/b ratios. Chlorophylls a and b are both associated with the light-harvesting antennae, while only Chl a is found in the reaction centres. A lower a/b ratio, therefore, reflects an increase in LHCII complexes relative to reaction centres (see Chapter 1, Section 1.2).
influencing photosynthesis, light quality and ..
In addition to differences in leaf anatomy and chloroplast ﬁne structure, energy derived from absorbed sunlight is processed in ways that differ subtly between shade-grown and sun-grown plants. In high light, there is a requirement for greater capacity in both the light and CO2 fixation reactions of photosynthesis. Photosynthesis–light response curves for shade and sun plants (Figure 12.7) illustrate such differences. The initial slope of each light response curve represents the quantum or photon efﬁciency of photosynthesis. This is the same for sun and shade plants. The reason it does not change is that the efﬁciency of the light reactions is the same irrespective of how much light has been received during growth (i.e. eight photons are required for the evolution of one molecule of O2 and ﬁxation of one molecule of CO2 in all plants).
Photosynthesis Light Independent Reaction - YouTube
Once sunlight has been intercepted by an assimilatory organ, photon absorption then depends on the extent and nature of light-absorbing pigments in the photosynthetic tissues. In terrestrial plants, the major light-absorbing pigments are chlorophylls a and b plus a range of carotenoids which can act as accessory pigments. Compared with high-light plants, plants grown in low light tend to allocate relatively more resources to their light-harvesting pigments and the associated proteins than to the enzyme Rubisco and other soluble proteins involved in CO2 ﬁxation. This shift in allocation of nitrogen-based resources can be accompanied by marked changes in leaf anatomy, especially depth of mesophyll tissue (see Case study 12.1) and reflects a need for increased efﬁciency of light absorption when sunlight is limited.
In the darkness of December, light is important in fact and symbolism
Figure 12.7 Photosynthesis-light response curve for typical shade and sun plants, showing relationships between photosynthetic rate and absorbed light (expressed as a photon irradiance). Dashed lines are extrapolations of initial linear slopes where photosynthesis is light limited, and represent quantum yield (moles of O2 evolved per mole quanta absorbed). (Original data courtesy S.A. Robinson)
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