Changes in the Photosynthetic Properties of Australian Wheat Cultivars Over the Last Century

1994 ◽  
Vol 21 (2) ◽  
pp. 169 ◽  
Author(s):  
N Watanabe ◽  
JR Evans ◽  
WS Chow
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Leaf Area ◽  
Chlorophyll A ◽  
Wheat Cultivars ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Partial Pressures ◽  
Australian Wheat ◽  
Photosynthetic Properties

A selection of Australian wheat cultivars, representative of those widely cultivated over the last century, was grown in the glasshouse. Photosynthetic properties of the flag leaves were determined as well as the chlorophyll, soluble protein, nitrogen and photosystem II content of the leaves. The rate of electron transport was calculated from gas exchange measurements at high CO2 partial pressures or from chlorophyll fluorescence. We found a trend towards higher rates of CO2 assimilation, higher chlorophyll and nitrogen contents per unit leaf area over time. The increase in leaf nitrogen and photosynthetic rate is most probably due to the introduction of the Rht dwarfing genes. Counter to this we observed declines in rate of electron transport per unit chlorophyll, chlorophyll a/b ratio and photosystem II content per unit chlorophyll. Because the chlorophyll to nitrogen ratio was similar between cultivars, lowering of the rate of electron transport per unit chlorophyll in modern cultivars results in a fall in the rate of electron transport per unit of nitrogen. There was no variation in the ratio of intercellular to ambient CO2 partial pressures, or leaf mass per unit leaf area. The comparison of a near isogenic pair, with or without a portion of a rye chromosome that is associated with high yield, did not reveal any association with photosynthetic characteristics. It is suggested that selection for higher chlorophyll a/b ratios for a given leaf chlorophyll content may provide a feasible surrogate for selecting higher photosynthetic capacity.

Photosynthetic Responses to Phosphorus Nutrition in Eucalyptus grandis Seedlings

1990 ◽  
Vol 17 (5) ◽  
pp. 527 ◽  
Author(s):  
MUF Kirschbaum ◽  
D Tompkins
Keyword(s):  
Nitrogen Content ◽  
Leaf Area ◽  
Eucalyptus Grandis ◽  
Phosphorus Nutrition ◽  
Assimilation Rate ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Leaf Weight ◽  
Partial Pressures ◽  
Phosphorus Status

Eucalyptus grandis seedlings were grown in growth units in which plant roots were suspended in air while continuously being sprayed with nutrient solution (aeroponic system). Phosphorus was added to nutrient solutions in exponentially increasing amounts which determined plant growth rates. Plants were grown at five relative phosphorus addition rates, and photosynthetic performance of leaves was compared across treatments. Carbon assimilation rates ranged from 11.7 μmol m-2 s-1 for plants with lowest phosphorus status to 23.1 μmol m-2 s-1 for plants with highest phosphorus status. Intercellular partial pressures of CO2 concomitantly decreased from 260 pbar for plants with lowest to 220 μbar for plants with highest phosphorus status. Leaves in all treatments showed a decrease in assimilation rate at intercellular partial pressures of CO2 above c. 600 μbar. There was no consistent correlation between the extent of that decrease and the phosphorus status of leaves. Assimilation rates were correlated with leaf phosphorus content. This relationship was apparent on either a unit leaf area or unit leaf weight basis. Assimilation rates and leaf nitrogen content per unit leaf weight were also correlated. In contrast, there was no correlation between leaf assimilation rate per unit leaf area and nitrogen content per unit leaf area, as nitrogen content per unit area was similar for all phosphorus treatments. The differences between correlations on a weight and area basis were due to differences in specific leaf area in different treatments, with plants with lower phosphorus status having less leaf area per unit leaf weight. The photosynthetic measurements showed that CO2 assimilation rate, together with relative leaf growth rate, was one of the processes most sensitive to phosphorus nutrition.

Photosynthetic Responses of Pisum sativum to an Increase in Irradiance During Growth. I. Photosynthetic Activities

1987 ◽  
Vol 14 (1) ◽  
pp. 1 ◽  
Author(s):  
WS Chow ◽  
JM Anderson
Keyword(s):  
Electron Transport ◽  
Leaf Area ◽  
Time Course ◽  
High Light ◽  
Lag Phase ◽  
Total Chlorophyll ◽  
Bisphosphate Carboxylase ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Photosynthetic Activities

The extent and time course of changes in photosynthetic activities of leaves and isolated chloroplasts was followed in pea plants which were adapted to low light (60 �mol photons m-2 s-1, 400-700 nm, 16 h light/ 8 h dark cycles), and subsequently transferred to higher light (390 �mol photons m-2 s-1). The photosynthetic rates of leaves in CO2-saturating conditions, measured at light saturation or subsaturation, increased with no noticeable lag, doubling within 1 week after transfer to high light. In contrast, the increase of in vitro ribulose-1,5-bisphosphate carboxylase activity (~ 130%) and photosystem II electron transport capacity (~ 60%) occurred with an apparent lag of - 1 day after transfer to high light. The capacity for uncoupled whole-chain electron transport also increased slowly (~ 70%). Whilst the total chlorophyll (Chl) per unit leaf area remained steady, the Chl a/Chl b ratio increased with no apparent lag phase from 2.7 in low irradiance to 3.2 in high irradiance within 1 week. The results demonstrate that, following an increase of growth irradiance, pea leaves readily increase the capacity for utilising high light effectively, even when the total chlorophyll per unit leaf area remained constant. However, a better understanding of the time course of response requires measurements of other chloroplast parameters.

Effects of Nitrogen Nutrition on Electron Transport Components and Photosynthesis in Spinach

1987 ◽  
Vol 14 (1) ◽  
pp. 59 ◽  
Author(s):  
JR Evans ◽  
I Terashima
Keyword(s):  
Electron Transport ◽  
Nitrogen Content ◽  
Leaf Area ◽  
Oxygen Evolution ◽  
Soluble Protein ◽  
Nitrogen Deficiency ◽  
Cytochrome F ◽  
Reaction Centre ◽  
Unit Leaf Area ◽  
Unit Leaf

Spinach plants (Spinacia oleracea L.) were grown in hydroponic culture in a glasshouse under full sunlight. They were supplied with different concentrations of nitrate nitrogen in solution, ranging from 1 to 12 mM, in order to produce leaves with different nitrogen contents. Oxygen evolution at CO2 saturation was measured as a function of absorbed irradiance in leaf discs with an oxygen electrode. Electron transport activities, reaction centre densities, cytochrome f and plastoquinone contents, RuP2 carboxylase and coupling factor activities and soluble protein content were measured in similar material. Although nitrogen and chlorophyll contents per unit leaf area were reduced by 60% by nitrogen deficiency, when expressed on a chlorophyll basis, thylakoid components, electron transport activities and the rate of oxygen evolution at CO2 saturation were similar between nitrogen treatments. In contrast, the content of soluble protein and RuP2 carboxylase expressed on a chlorophyll basis was greater the greater the nitrogen content per unit leaf area. Therefore the ratio of RuP2 carboxylase activity to electron transport activity increased in leaves having greater nitrogen content.

Stomatal Development During Leaf Expansion in Tobacco and Sunflower

1975 ◽  
Vol 23 (2) ◽  
pp. 253 ◽  
Author(s):  
HM Rawson ◽  
CL Craven
Keyword(s):  
Leaf Area ◽  
Stomatal Density ◽  
Stomatal Development ◽  
Developmental Patterns ◽  
Full Size ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Wide Range ◽  
Young Leaves ◽  
Different Levels

Changes in stomatal density and size were followed in tobacco and sunflower leaves expanding from 10% of final area (10% Amax) to Amax under different levels of radiation. Lower radiation increased final leaf area, reduced stomatal densities, and increased area per stoma but had little effect on stomatal area per unit leaf area at Amax. In very young leaves (20% Amax) there was a wide range in the sizes of individual stomata, some stomata being close to full size, but by Amax differences were small. The possible relationship between the developmental patterns described and photosynthesis is briefly discussed.

Effect of Interspecific Interference, Light Intensity, and Soil Moisture on Soybean (Glycine max), Common Cocklebur (Xanthium strumarium), and Sicklepod (Cassia obtusifolia) Water Uptake

Weed Science ◽  
1993 ◽  
Vol 41 (4) ◽  
pp. 534-540 ◽  
Author(s):  
Ronald E. Jones ◽  
Robert H. Walker
Keyword(s):  
Soil Moisture ◽  
Light Intensity ◽  
Leaf Area ◽  
Water Uptake ◽  
Root Weight ◽  
Pressure Potential ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Shoot Weight ◽  
The Relationship

Greenhouse and growth chamber experiments with potted plants were conducted to determine the effects of interspecific root and canopy interference, light intensity, and soil moisture on water uptake and biomass of soybean, common cocklebur, and sicklepod. Canopy interference and canopy plus root interference of soybean with common cocklebur increased soybean water uptake per plant and per unit leaf area. Root interference with soybean decreased common cocklebur water uptake per plant. Canopy interference of soybean with sicklepod increased soybean water uptake per unit leaf area, while root interference decreased uptake per plant. Combined root and canopy interference with soybean decreased water uptake per plant for sicklepod. Soybean leaf area and shoot weight were reduced by root interference with both weeds. Common cocklebur and sicklepod leaf area and shoot weight were reduced by root and canopy interference with soybeans. Only common cocklebur root weight decreased when canopies interfered and roots did not. The relationship between light intensity and water uptake per unit leaf area was linear in both years with water uptake proportional to light intensity. In 1991 water uptake response to tight was greater for common cocklebur than for sicklepod. The relationship between soil moisture level and water uptake was logarithmic. Common cocklebur water uptake was two times that of soybean or sicklepod at −2 kPa of pressure potential. In 1991 common cocklebur water uptake decreased at a greater rate than soybean or sicklepod in response to pressure potential changes from −2 to −100 kPa.

Carbon Isotope Discrimination and Gas Exchange in Coffea arabica During Adjustment to Different Soil Moisture Regimes

1992 ◽  
Vol 19 (2) ◽  
pp. 171 ◽  
Author(s):  
FC Meinzer ◽  
NZ Saliendra ◽  
C Crisosto
Keyword(s):  
Soil Moisture ◽  
Gas Exchange ◽  
Leaf Area ◽  
Coffea Arabica ◽  
Carbon Isotope Discrimination ◽  
Total Leaf Area ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Moisture Regimes ◽  
Area Basis

Although carbon isotope discrimination (Δ) has been reported to decline in plants growing under reduced soil moisture, there is little information available concerning the dynamics of adjustments in Δ and gas exchange following a change in soil water availability. In this study Δ, photosynthetic gas exchange, and growth were monitored in container-grown coffee (Coffea arabica L.) plants for 120 days under three soil moisture regimes. At the end of 120 d, total leaf area of plants irrigated twice weekly was one half that of plants irrigated twice daily, although their assimilation rates on a unit leaf area basis were nearly equal throughout the experiment. This suggested that maintenance of nearly constant photosynthetic characteristics on a unit leaf area basis through maintenance of a smaller total leaf area may constitute a major mode of adjustment to reduced soil moisture availability in coffee. Intrinsic water-use efficiency (WUE) predicted from foliar Δ values was highest in plants irrigated weekly, intermediate in plants irrigated twice weekly and lowest in plants irrigated twice daily. When instantaneous WUE was estimated from independent measurements of total transpiration per plant and assimilation on a unit leaf area basis, the reverse ranking was obtained. The lack of correspondence between intrinsic and instantaneous WUE was attributed to adjustments in canopy morphology and leaf size in the plants grown under reduced water supply which enhanced transpiration relative to assimilation. Values of Δ predicted from the ratio of intercellular to ambient CO2 partial pressure determined during gas exchange measurements were not always consistent with measured foliar Δ. This may have resulted from a patchy distribution of stomatal apertures in plants irrigated weekly and from a lag period between adjustment in gas exchange and subsequent alteration in Δ of expanding leaves. The importance of considering temporal and spatial scales, and previous growth and environmental histories in comparing current single leaf gas exchange behaviour with foliar Δ values is discussed.

Photosynthetic Acclimation of Alocasia macrorrhiza (L.) G. Don

1988 ◽  
Vol 15 (2) ◽  
pp. 107 ◽  
Author(s):  
WS Chow ◽  
L Qian ◽  
DJ Goodchild ◽  
JM Anderson
Keyword(s):  
Charge Density ◽  
Leaf Area ◽  
Cell Walls ◽  
Surface Charge Density ◽  
Leaf Tissue ◽  
O2 Evolution ◽  
Palisade Cell ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Growth Irradiance

The photosynthetic acclimation of Alocasia macrorrhiza (L.) G. Don, a species naturally occurring in deep shade in rainforests, has been studied in relation to a wide range of controlled irradiances during growth (~3-780 �mol photons m-2 s-1 of fluorescent or incandescent light, 10 h light/ 14 h dark). At the maximum growth irradiances, the light- and CO2-saturated rates of O2 evolution per unit leaf area were ~4 times as high as at low irradiance, and approached those of glasshouse-grown spinach. Growth at maximum irradiances reduced the quantum yield of O2 evolution only slightly. Changes in the anatomy of leaf tissue, the ultrastructure of chloroplasts and the composition of chloroplast components accompanied the changes in photosynthetic functional characteristics. At low growth irradiance, palisade cell chloroplasts were preferentially located adjacent to the distal periclinal cell walls and had large granal stacks, and the destacked thylakoids had a very low surface charge density. In contrast, at higher growth irradiance, palisade cell chloroplasts were preferentially located adjacent to the anticlinal cell walls; they had small granal stacks, large stromal space, and a high surface charge density on the destacked thylakoids. The number of chloroplasts per unit section length increased with growth irradiance. Ribulosebisphosphate carboxylase activity per unit leaf area increased markedly with irradiance. Photosystem II, cytochrome f and latent ATPase activity per unit chlorophyll increased to a lesser extent. While the chlorophyll a/chlorophyll b ratio increased substantially with growth irradiance, the chlorophyll content per unit leaf area declined slightly. Our results show that coordinated changes in the structure of leaf tissue, and the organisation and composition of chloroplast components are responsible for Alocasia being capable of acclimation to high as well as low irradiance.

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