scholarly journals Effect of Varying Crop Load on Leaf Photosynthesis and Carbon Isotope Discrimination of `Imperial Gala' Apple Tree

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1010C-1010
Author(s):  
Paolo Sabbatini ◽  
James Flore
Keyword(s):  
Water Stress ◽  
Carbon Isotope ◽  
Photosynthetic Rate ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Composition ◽  
Research Station ◽  
Crop Load ◽  
13C Discrimination ◽  
Source Limitation

Crop load (CL) is a critical regulator of production and quality on apple. It affects leaf photosynthetic rate and usually an increase is detected in leaves close to developing sinks. The objective of this work was to test if 13C discrimination during photosynthesis could be an indicator of carbon sink limitation. The natural plant carbon isotope composition (13C/12C ratio: d13C) is an indicator of water use efficiency and it is an effective tool to study environmental stresses in plants. Seven-year-old trees of Imperial Gala/Bud 9 (n=30), field-grown at the Clarksville Horticultural Research Station in Michigan, were hand-thinned to five levels of CL manipulating the leaf to fruit ratio (LFR: 4, 8, 16, 32, 64) after June drop. Net photosynthetic rate (A) of leaves was monitored daily during the season and elevated rates were observed in low LFR. The A was inhibited in low CL trees (LFR 32 and 64) more in the afternoon (from 20% to 42% in relation to normal CL: LFR 16) than in the morning (from 5% to 20%), and stomatal conductance declined over the afternoon. Shoot and fruit growth were affected (fruit size –11/+11%, shoot length –13/+18% from normal CL; LFR 16). Variations of the stable carbon isotope composition of leaves show a significant reduction of 13C discrimination in low CL trees (–3.2%: d13C –25.82) and an increase of 13C discrimination (+2.7%: d13C –27.38) in relation to normal CL trees (LFR 15.63). The results were similar to those reported in 2004, which imply isotopic discrimination in relation to source limitation. This is the opposite of what you would expect under water stress conditions. Although trees were well-watered during the season, the effect of water stress on apple trees and its interaction with source limitation will be discussed.

scholarly journals Effect of Crop Load on Diurnal Leaf Photosynthesis, Stomatal Conductance, and Annual Carbon Isotope Composition of `Imperial Gala' Apple Tree

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1096C-1096
Author(s):  
Paolo Sabbatini ◽  
James A. Flore
Keyword(s):  
Carbon Isotope ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Carbon Isotope Composition ◽  
Sink Strength ◽  
Research Station ◽  
Old Field ◽  
Crop Load ◽  
Annual Carbon ◽  
Source Sink

The naturally occurring carbon isotope composition (or 13C: 12C ratio, expressed with the notation d13C) of plant tissue may be used as an indicator of water use efficiency during plant growth. d13C has been shown to be an effective tool to study physiological response of plant to environmental conditions, especially water stress. The objective of this work was to test if d13C could be an indicator of carbon limitations or a low source: sink ratio. Trees of `Imperial Gala'/Bud 9 (n = 12), 6-years-old, field grown at the Clarksville Horticultural Research Station (Clarksville, Miss.), were assessed with different crop load (LCL = Low Crop Load, 0.76 ± 0.44 fruit per trunk sectional area (TCA); NCL = Normal Crop Load, 7.25 ± 1.83 fruit/TCA; HCL = High Crop Load, 15.83 ± 1.76 fruit/TCA) and leaf: fruit ratio (LCL: 52.78 ± 8.55, NCL: 13.33 ± 3.06, HCL; 4.31 ± 0.68) immediately following June drop. Net photosynthetic rate of leaves were monitored during the season and elevated rates were observed in NCL and HCL and correlated with the fruiting process. Photosynthesis was inhibited in LCL more in the afternoon (from 20% to 42% in relation to NCL) than in the morning (from 5% to 20%) and this was positively correlated with crop sink strength. Variations of the stable carbon isotope composition of roots (fine and coarse), fruit, leaves, and current-year stems were examined. The d13C varied by tissue (fruit > shoot and leaf > root) and in relation to the level of crop load (d13C‰ in fruit: LCL –23.513 ± 0.248, NCL –24.891 ± 0.594; and HCL –24.935 ± 0.375). These results may have implications for analysis of isotopic signals in carbohydrate stress and fractionation steps will be discussed.

scholarly journals High time-resolved measurement of stable carbon isotope composition in water-soluble organic aerosols: method optimization and a case study during winter haze in East China

2018 ◽  
Author(s):  
Wenqi Zhang ◽  
Yan-Lin Zhang ◽  
Fang Cao ◽  
Yankun Xiang ◽  
Yuanyuan Zhang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Organic Aerosols ◽  
Carbon Isotope Composition ◽  
Water Soluble ◽  
High Time ◽  
Stable Carbon ◽  
Air Mass

Abstract. Water soluble organic carbon (WSOC) is a significant fraction of organic carbon (OC) in atmospheric aerosols. WSOC is of great interest due to its significant effects on atmospheric chemistry, the Earth’s climate and human health. Stable carbon isotope (δ13C) can be used to track the potential sources and investigate atmospheric processes of organic aerosols. In this study, a method of simultaneously measuring the mass concentration and δ13C values of WSOC from aerosol samples is established by coupling the Gas Bench II preparation device with isotopic ratio mass spectrometry. The precision and accuracy of isotope determination is better than 0.17 ‰ and 0.5 ‰, respectively, for samples containing carbon larger than 5 μg. This method is then applied for the high time-resolution aerosol samples during a severe wintertime haze period in Nanjing, East China. WSOC varies between 3–32 μg m−3, whereas δ13C-WSOC ranges from −26.24 ‰ to −23.35 ‰. Three different episodes (e.g., namely the Episode 1, the Episode 2, the Episode 3) are identified in the sampling period, showing a different tendency of δ13C-WSOC with the accumulation process of WSOC aerosols. The increases in both the WSOC mass concentrations and the δ13C-WSOC values in the Episode 1 indicate that WSOC is subject to a substantial photochemical aging during the air mass transport. In the Episode 2, the decline of the δ13C-WSOC is accompanied by the increase in the WSOC mass concentrations, which is associated with regional-transported biomass burning emissions. In the Episode 3, heavier isotope (13C) is exclusively enriched in total carbon (TC) compares to WSOC aerosols. This suggests that water-insoluble carbon may contain 13C-enriched components such as dust carbonate which is supported by the enhanced Ca2+ concentrations and air mass trajectories analysis. The present study provides a novel method to determine stable carbon isotope composition of WSOC and it offers a great potential to better understand the source emission, the atmospheric aging and the secondary production of water soluble organic aerosols.

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