Effects of Shade on Gas Exchange and Growth in Seedlings of Eucalyptus grandis Hill ex Maiden

1978 ◽  
Vol 5 (6) ◽  
pp. 723 ◽  
Author(s):  
D Doley
Keyword(s):  
Dry Matter ◽  
Eucalyptus Grandis ◽  
Light Response ◽  
Light Treatment ◽  
Unit Weight ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Low Light ◽  
Unit Leaf ◽  
Leaf Volume

E. grandis seedlings grown under conditions of high (12.6) and low (2.8 Em-2 day-) daily integrals of photon flux density exhibited the same light response of photosynthesis when the rates were expressed on a unit leaf volume basis. The conversion of photosynthetic substrate to dry matter was more efficient in larger than in smaller plants. Allocation of dry matter between leaves, stem and roots was influenced relatively little by the shading treatments, but the utilization of dry matter by the leaves and stem was affected. Plants raised under low light exhibited significantly greater areas per unit weight of leaf, and significantly greater lengths per unit weight of stem than did plants raised in the high-light treatment. Adaptation to shading in E. grandis seedlings was judged to be limited. A model was constructed which described adequately the growth of these seedlings after the age of about 14 days.

Responses of Rainforest Understorey Plants to Excess Light during Sunflecks

1997 ◽  
Vol 24 (1) ◽  
pp. 17 ◽  
Author(s):  
Jenny R. Watling ◽  
Sharon A. Robinson ◽  
Ian E. Woodrow ◽  
C. Barry Osmond
Keyword(s):  
Tropical Rainforest ◽  
Photon Flux ◽  
Photochemical Quenching ◽  
Photon Flux Density ◽  
Leaf Angle ◽  
Low Light ◽  
Fourth Species ◽  
Excess Light ◽  
Understorey Plants ◽  
Non Photochemical Quenching

Responses of Alocasia macrorrhiza (L.) G. Don, Castanospora alphandii (F. Muell.) F. Muell. and Alpinia hylandii R. Smith, growing in a tropical rainforest understorey, to excess light during sunflecks were investigated using chlorophyll fluorescence techniques and by analysing xanthophyll cycle activity. A fourth species, the pioneerOmalanthus novo-guineensis (Warb.) Schum., growing in a small gap, was also studied. In all three understorey species there were large and rapid decreases in the proportion of open Photosystem II (PSII) centres, as indicated by qP, on illumination with saturating light and a concurrent increase in non-photochemical quenching. qP remained low (< 0.4) throughout the period of illumination (~15 min), although it did increase gradually, probably reflecting photosynthetic induction. Sustained declines (up to 120 min) in quantum yield, indicated by Fv/Fm, occurred in all three understorey species following exposure to saturating Photon flux density (PFD) during sunflecks. When ?PSII was monitored during sunflecks it was found to be very sensitive to changes in PFD, declining rapidly with even modest rises in the latter. There was rapid and continuing net conversion of violaxanthin (V) to antheraxanthin plus zeaxanthin (A+Z) on exposure of A. macrorrhiza and C. alphandii to saturating sunflecks. On returning to low light A. macrorrhiza retained its high levels of A+Z for up to 60 min, while C. alphandii rapidly converted back to V. O. novo- guineensis responded to high light by changing its leaf angle to reduce interception and showed no indication of photoinhibition during or after exposure.

scholarly journals Response of CO 2 -starved diatom Phaeodactylum tricornutum to light intensity transition

2017 ◽  
Vol 372 (1728) ◽  
pp. 20160396 ◽  
Author(s):  
Parisa Heydarizadeh ◽  
Wafâa Boureba ◽  
Morteza Zahedi ◽  
Bing Huang ◽  
Brigitte Moreau ◽  
...  
Keyword(s):  
Flux Density ◽  
Carbon Metabolism ◽  
Phaeodactylum Tricornutum ◽  
Shikimate Pathway ◽  
Aromatic Amino Acids ◽  
Molecular Data ◽  
High Light ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Low Light

In this study, we investigated the responses of Phaeodactylum tricornutum cells acclimated to 300 µmol m −2 s −1 photon flux density to an increase (1000 µmol m −2 s −1 ) or decrease (30 µmol m −2 s −1 ) in photon flux densities. The light shift occurred abruptly after 5 days of growth and the acclimation to new conditions was followed during the next 6 days at the physiological and molecular levels. The molecular data reflect a rearrangement of carbon metabolism towards the production of phosphoenolpyruvic acid (PEP) and/or pyruvate. These intermediates were used differently by the cell as a function of the photon flux density: under low light, photosynthesis was depressed while respiration was increased. Under high light, lipids and proteins accumulated. Of great interest, under high light, the genes coding for the synthesis of aromatic amino acids and phenolic compounds were upregulated suggesting that the shikimate pathway was activated. This article is part of the themed issue ‘The peculiar carbon metabolism in diatoms’.

scholarly journals Photochemical Acclimation of Three Contrasting Species to Different Light Levels: Implications for Optimizing Supplemental Lighting

2017 ◽  
Vol 142 (5) ◽  
pp. 346-354 ◽  
Author(s):  
Shuyang Zhen ◽  
Marc W. van Iersel
Keyword(s):  
Electron Transport ◽  
Light Intensity ◽  
Photochemical Efficiency ◽  
Light Response ◽  
High Light ◽  
Photon Flux ◽  
Ambient Light ◽  
Response Curves ◽  
Low Light ◽  
Supplemental Lighting

Photosynthetic responses to light are dependent on light intensity, vary among species, and can be affected by acclimation to different light environments (e.g., light intensity, spectrum, and photoperiod). Understanding how these factors affect photochemistry is important for improving supplemental lighting efficiency in controlled-environment agriculture. We used chlorophyll fluorescence to determine photochemical light response curves of three horticultural crops with contrasting light requirements [sweetpotato (Ipomea batatas), lettuce (Lactuca sativa), and pothos (Epipremnum aureum)]. We also quantified how these responses were affected by acclimation to three shading treatments-full sun, 44% shade, and 75% shade. The quantum yield of photosystem II (ΦPSII), a measure of photochemical efficiency, decreased exponentially with increasing photosynthetic photon flux (PPF) in all three species. By contrast, linear electron transport rate (ETR) increased asymptotically with increasing PPF. Within each shading level, the high-light-adapted species sweetpotato used high light more efficiently for electron transport than light-intermediate lettuce and shade-tolerant pothos. Within a species, plants acclimated to high light (full sun) tended to have higher ΦPSII and ETR than those acclimated to low light (44% or 75% shade). Nonphotochemical quenching (NPQ) (an indicator of the amount of absorbed light energy that is dissipated as heat) was upregulated with increasing PPF; faster upregulation was observed in pothos as well as in plants grown under 75% shade. Our results have implications for supplemental lighting: supplemental light is used more efficiently and results in a greater increase in ETR when provided at low ambient PPF. In addition, high-light-adapted crops and crops grown under relatively high ambient light can use supplemental light more efficiently than low-light-adapted crops or those grown under low ambient light.

scholarly journals Light response and photosynthesis in sorghum under field conditions

MAUSAM ◽  
2022 ◽  
Vol 46 (3) ◽  
pp. 303-306
Author(s):  
Y. R. KENJLE ◽  
M. C. VARSHNEYA ◽  
T. R. U. NAIDU
Keyword(s):  
Correlation Coefficients ◽  
Light Response ◽  
Photosynthetic Photon Flux Density ◽  
Field Conditions ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Response Curves ◽  
Light Response Curves ◽  
Air Temperatures ◽  
Rate Of Photosynthesis

ABSTRACT. The diurnal variation of rate of photosynthesis (l') with photosynthetic photon flux density (PPFD) model of light response curves and the relationship between PPFD and P were studied for two postmonsoon (rabi) sorghum genotypes, viz.. M35- I and RSV-9R under field conditions at Pune. The half maximal values. i.e., PPFD level at which P=Pmax/2 obtained were 1251 and 937 umolm-2s-1 for M35-l and RSV.9R respectively. The potential rates of photosynthesis were 65,79 and 64.52  umolm-2S-1 whereas the observed maximum rates of photosynthesis were lower. 40.93 and 46.66 umolm-2s-1 in M35-1 and RSV-9R Respectively, due to effect of air temperatures under the field conditions, n1e maximum rate of photosynthesis determined from the model decreased with delay in the sowing of the crop. Correlation coefficients between PPFD and rate of photosynthesis were 0,794 and 0,708 for M35-1 and RSV-9R respectively. The PPFD received and rate of photosynthesis decreased significantly with delay in sorghum sowing.    

Genotypic Variation in Light and Temperature Response of Photosynthesis in Nothofagus solandri Var. cliffortioides and N. menziesii

1996 ◽  
Vol 23 (4) ◽  
pp. 421 ◽  
Author(s):  
OJ Sun ◽  
GB Sweet
Keyword(s):  
New Zealand ◽  
Dark Respiration ◽  
Genotypic Variation ◽  
Temperature Response ◽  
Light Response ◽  
Net Photosynthesis ◽  
Photosynthetic Photon Flux Density ◽  
Ecosystem Dynamics ◽  
Photon Flux ◽  
Photon Flux Density

Responses of photosynthesis to light and temperature were studied in two Nothofagus species native to New Zealand: N. solandri var. cliffortioides (Hook. f.) Poole and N. menziesii (Hook. f.) Oerst.. Measurements of leaf photosynthesis were made in a controlled environment growth chamber at photosynthetic photon flux density between 0 and 700 μmol m-2 s-1 with temperatures set for 10, 20 and 25�C, on seedlings previously grown in a glasshouse from seed of three different origins. In both species, pronounced intraspecific variation was shown in dark respiration, light compensation point and light-saturated net photosynthesis (Amax). Seedlings of N. solandri showed higher dark respiration and light compensation levels than N. menziesii seedlings, but the two species did not differ in Amax. Change in temperature resulted in significant change in the response of photosynthesis to light in both N. solandri and N. menziesii. The differences between N. solandri and N. menziesii in light response of photosynthesis are discussed in terms of ecosystem dynamics of Nothofagus forests in New Zealand.

Interacting Effects of CO2and Nutrient Concentration

Weed Science ◽  
1982 ◽  
Vol 30 (4) ◽  
pp. 389-394 ◽  
Author(s):  
David T. Patterson ◽  
Elizabeth P. Flint
Keyword(s):  
Dry Matter ◽  
Dry Matter Production ◽  
Photon Flux ◽  
Nutrient Level ◽  
Photon Flux Density ◽  
Growth Enhancement ◽  
Chlorophyll Contents ◽  
Leaf Chlorophyll ◽  
Matter Production ◽  
Half Strength

Soybean [Glycine max(L.) Merr. ‘Tracy′] and two associated weeds, sicklepod (Cassia obtusifoliaL.) and showy crotalaria (Crotalaria spectabilisRoth), were grown in controlled-environment chambers with day/night temperatures of 29/23 C, photosynthetic photon flux density (PPFD) of 600 μE·m−2·s-1, CO2concentrations of 350 or 675 ppm, and one-eighth or one-half strength Hoagland's nutrient solution applied three times daily. Leaf areas and dry weights of plant parts were determined at 1, 3, and 5 weeks. Stomatal resistances, transpiration rates, leaf water potentials, and leaf chlorophyll contents were measured, and net assimilation rates (NAR) and leaf area durations (LAD) were calculated. In all species, growth in 675 ppm CO2enhanced dry-matter production through increases in both NAR and LAD. The increased dry-matter production with one-half strength compared to one-eighth strength Hoagland's solution was, however, caused by increased LAD. Stomatal conductances and transpiration rates decreased in 675 ppm CO2, but were not affected by nutrient level. High CO2concentration or low nutrient level generally decreased leaf chlorophyll content per unit area. Growth enhancement by high CO2was greater in one-half strength than in one-eighth strength Hoagland's solution.

The Effect of Photoperiod, Temperature and Photon Flux Density on Flowering in Pimelea ciliata

1994 ◽  
Vol 42 (5) ◽  
pp. 575 ◽  
Author(s):  
AT Slater ◽  
PR Franz ◽  
WK Thompson
Keyword(s):  
Flux Density ◽  
Flowering Plant ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Apparent Effect ◽  
Low Light ◽  
Flowering Response ◽  
High Photon Flux

A range of photoperiods were investigated to determine their effect on newer induction in Pimelea ciliata. Temperatures and photon flux densities were also investigated to determine their effect on modifying the response to photoperiod. Pimelea ciliata developed flowers on all plants after exposure to at least 4 weeks of an 8 h photo- and thermoperiod at a high photon flux density. As the time under the 8 h photo- and thermoperiod increased, the total number of flowers produced and the percentage of buds which were floral on each flowering plant increased. Plants gown under a 16 or 10 h photoperiod for up to 8 weeks did not produce any flowers. Under a 12 h photoperiod, only two plants out of 36 flowered, and they produced a low number of flowers. Under the conditions tested, temperature had no apparent effect on the number of plants which flowered or the number of flowers on each flowering plant. However, a vernalisation response may be increasing the rate of flowering. The flowering response was reduced when plants were grown under a low photon flux density. Few plants produced flowers, and the percentage of shoots that were floral was also reduced under low light.

Effect of Corn-Induced Shading on Dry Matter Accumulation, Distribution, and Architecture of Redroot Pigweed (Amaranthus retroflexus)

Weed Science ◽  
1993 ◽  
Vol 41 (4) ◽  
pp. 568-573 ◽  
Author(s):  
Stephane M. Mclachlan ◽  
Matthijs Tollenaar ◽  
Clarence J. Swanton ◽  
Stephan F. Weise
Keyword(s):  
Leaf Area ◽  
Dry Matter ◽  
Plant Architecture ◽  
Amaranthus Retroflexus ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Dry Matter Accumulation ◽  
Branch Number ◽  
Dry Matter Distribution ◽  
Redroot Pigweed

A fundamental component of modeling crop interference is the effect of understory photosynthetic photon flux density (PPFD) on weed architecture and growth. The effect of decreased PPFD on spaced redroot pigweed dry matter accumulation, distribution, and plant architecture was quantified by increasing corn density and delaying weed planting date. As canopy-transmitted PPFD declined, total dry matter accumulation decreased and relative dry matter distribution was greater to main-stem components than to branch components. Increased rectangularity in understory weed architecture was associated with a concomitant decrease in branch number. The proportion of leaf area and dry matter in the upper segment of the redroot pigweed increased as PPFD declined with increased corn density. Results suggest that changes in plant architecture, as influenced by canopy-transmitted PPFD, may be as important as those of total dry matter and leaf area when describing and predicting the effects of crop-weed interference.

Comparative carbon dioxide exchange for two Populus clones grown in growth room, greenhouse, and field environments

1984 ◽  
Vol 14 (6) ◽  
pp. 924-932 ◽  
Author(s):  
Neil D. Nelson ◽  
Paul Ehlers
Keyword(s):  
Net Photosynthetic Rate ◽  
Leaf Area ◽  
Photosynthetic Rate ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Growth Environment ◽  
Photosynthetic Rates ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Growth Room

Light-saturated net photosynthetic rates per unit leaf area were 1.6–2.1 times greater for the photosynthetically mature leaves of plants of two hybrid Populus clones (NC-5260, 'Tristis No.1' (Populustristis Fisch. × P. balsamifera L.); NC-5326, 'eugenei' (P. deltoides Bartr. ex Marsh. × P. nigra L.)) grown in pots in the field than in comparable plants from a controlled environment growth room and a winter greenhouse. Stomatal resistances to CO2 in the field trees were only 0.4–0.6 of those in growth room and greenhouse trees. Mesophyll (residual) resistances to CO2 in field trees were 0.4–0.8 of those in growth room and greenhouse trees. Field plants had specific leaf weights 1.5–1.8 times higher than growth room and greenhouse plants, likely primarily owing to the greater average photosynthetic photon flux density in the field (835, 225, and 142 μE m−2 s−1 for field, growth room, and greenhouse conditions, respectively). When net photosynthetic rates (Ps) were corrected for the differences in specific leaf weights to derive net photosynthetic rate per unit leaf dry weight, the values were similar for plants from the three environments (Ps in field trees was 0.9–1.2 times Ps in growth room and greenhouse trees); gross photosynthetic rates per unit leaf weight were even more similar. Internal leaf CO2 concentrations, and photorespiration and dark respiration rates per unit leaf area were not related to growth environment. However, photorespiration rate as a percentage of net photosynthetic rate was lower in the field trees (12–16% in field trees, 19–24% in growth room trees, and 23–39% in greenhouse trees). Net photosynthetic rate was shown to be under strong genetic control in these clones. The effects of growth environment on variables of carbon exchange are sensitive to the basis of expression of those variables.

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