Acclimation of Tomato Leaves to Changes in Light Intensity; Effects on the Function of the Thylakoid Membrane

The effect of natural shading on photosynthetic capacity and chloroplast thylakoid membrane function was examined in soybean (Glycine max. cv Young) under field conditions using a randomized complete block design. Seedlings were thinned to 15 plants per square meter at 20 days after planting. Leaves destined to function in the shaded regions of the canopy were tagged during early expansion at 40 days after planting. To investigate the response of shaded leaves to an increase in available light, plants were removed from certain plots at 29 or 37 days after tagging to reduce the population from 15 to three plants per square meter and alter the irradiance and spectral quality of light. During the transition from a sun to a shade environment, maximum photosynthesis and chloroplast electron transport of control leaves decreased by two-to threefold over a period of 40 days followed by rapid senescence and abscission. Senescence and abscission of tagged leaves were delayed by more than 4 weeks in plots where plant populations were reduced to three plants per square meter. Maximum photosynthesis and chloroplast electron transport activity were stabilized or elevated in response to increased light when plant populations were reduced from 15 to three plants per square meter. Several chloroplast thylakoid membrane components were affected by light environment. Cytochrome f and coupling factor protein decreased by 40% and 80%, respectively, as control leaves became shaded and then increased when shaded leaves acclimated to high light. The concentrations of photosystem I (PSI) and photosystem 11 (PSII) reaction centers were not affected by light environment or leaf age in field grown plants, resulting in a constant PSII/PSI ratio of 1.6 ± 0.3. Analysis of the chlorophyll-protein composition revealed a shift in chlorophyll from PSI to PSII as leaves became shaded and a reversal of this process when shaded leaves were provided with increased light. These results were in contrast to those of soybeans grown in a growth chamber where the PSII/ PSI ratio as well as cytochrome f and coupling factor protein levels were dependent on growth irradiance. To summarize, light environment regulated both the photosynthetic characteristics and the timing of senescence in soybean leaves grown under field conditions. ' Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the United States Department of Agriculture or the North Carolina Agricultural Research Service and does not imply its approval to the exclusion of other products that may also be suitable.Both light quantity and light quality regulate the photosynthetic properties of higher plants by controlling the activity and the composition of the photosynthetic apparatus (2, 5, 29). Thus, light environment plays a critical role during leaf expansion in determining the photosynthetic properties of the mature leaf. More recently, controlled environment studies with a number of species have shown that fully expanded leaves reta...

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Response of Soybean Photosynthesis and Chloroplast Membrane Function to Canopy Development and Mutual Shading

Burkey

Wells²

1991

“…2B) and photosynthetic electron transport ( (3,6,8,9). For each parameter in Figure 2, significant differences were observed within 1 to 3 d after transfer, whereas the complete response required 7 d. The slow acclimation kinetics observed here were typical of light acclimation processes that require the commitment of nutrients and metabolic energy to alter the biochemical composition of the leaf (3,6,8,9,16). The 64 kD polypeptide did not correspond to any intrinsic or extrinsic thylakoid membrane protein to which a function has been assigned.…”

Section: Analysis Of Thylakoid Membrane Activity and Polypeptide Compmentioning

confidence: 99%

“…The irradiance and spectral quality of light surrounding an individual leaf controls the capacity ofthat leafto conduct photosynthesis (1)(2)(3)10) and associated processes such as chloroplast electron transport (3,6,9,10) and photophosphorylation (4,7,10). Light regulates these photosynthetic activities by controlling the levels of specific chloroplast proteins associated with each function.…”

mentioning

confidence: 99%

Novel Light-Regulated Chloroplast Thylakoid Membrane Protein

Burkey¹

1992

A 64 kilodalton chloroplast membrane polypeptide was dependent on growth irradiance with 10-fold greater quantities of the protein present in barley (Hordeum vulgare) grown under 500 micromoles of photons per square meter per second compared with growth at 50 micromoles per square meter per second. The concentration of the protein was sensitive to changes in irradiance, with a slow time course for the response (days) similar to other reported light acclimation processes. The polypeptide also was observed in maize (Zea mays), oats (Avena sativa), and wheat (Triticum aestivum), but not in soybean (Glycine max Merr). The 64 kilodalton polypeptide did not correspond to any thylakoid membrane protein with an assigned function, so its structural or regulatory role is not known.

“…It is not surprising therefore that limiting N nutrition limits acclimation in these plants and others (13,19). Acclimation from shade to sun also depends on increases in other carbon reduction cycle enzymes and in electron transport and other photochemical activities (3,9). Despite these complex readjustments of the photosynthetic apparatus which occur during light acclimation in both Phaseolus and Alocasia, the acclimation process functions in such a way that a relatively constant relationship between the levels of carboxylation substrate (RuBP), carboxylation enzyme (RuBPCase), and product (PGA) is maintained ( …”

mentioning

confidence: 99%

Environmental Effects on Photosynthesis, Nitrogen-Use Efficiency, and Metabolite Pools in Leaves of Sun and Shade Plants

Seemann

Sharkey²,

Wang³

et al. 1987

292

174

ABSTRACIrEffects of varying light intensity and nitrogen nutrition on photosynthetic physiology and biochemistry were examined in the sun plant Phasolus vidgaris (common bean) and in the shade plant Alocasia macrorrhiza (Austalian rainforest floor species). In both Phaseolus and Alocauia, the differing growth regimes produced lrge changes in photosynthetic capacity and composition ofthe photosynthetic apparatus. COr saturated rates of photosynthesis were linearly related to leaf nitrogen (N) terized by significant alterations in the relative distribution of resources among the component parts of the photosynthetic apparatus (5). Light intensity also has a particularly dramatic effect on leaf N3 content, often a limiting resource for plant growth (14). A majority of this N in C3 plants is required for proteins involved in photosynthesis (10,25) and photosynthetic capacity is known to be generally proportional to leaf N content (6). A significant portion of any change in leaf N content which may result from differences in light intensity during growth is the result of a change in the concentration of RuBPCase3 (5), as RuBPCase represents approximately 20% of total N in leaves of well fertilized C3 sun plants (12,21). Changes in the activity of this enzyme are extremely well correlated with changes in photosynthetic capacity which occur with changes in the light intensity of growth (5), but it is unclear whether or not these changes represent an alteration in the relative proportion of total leaf N which has been allocated to this protein. Furthermore, it is important to understand how such changes affect the N-use efficiency of photosynthesis (8).We hypothesize that ifcertain components ofthe leafN budget predominate in the control of sun/shade acclimation, then redistribution of N among such key protein components of the photosynthetic apparatus may occur. Because large amounts of RuBPCase are required to support observed rates of photosynthesis in C3 plants and it is often rate-limiting for photosynthesis, comparative studies of environmental effects on N-use efficiency of photosynthesis in sun and shade plants should begin by assessing the relative importance of RuBPCase in the N budget of leaves grown under different environmental conditions. We have examined the effect of varying light intensity during growth, in combination with varying N availability, on photosynthetic performance, leaf N, RuBPCase, Chl, and metabolite pools of leaves. We have chosen to study two species, one of which is considered to be a 'sun plant' (Phaseolus vulgaris, common