Variation in transpiration efficiency and carbon isotope discrimination in cowpea

1999 ◽  
Vol 26 (6) ◽  
pp. 503 ◽  
Author(s):  
Ashok ◽  
I. S. Aftab Hussain ◽  
T. G. Prasad ◽  
G. C. Wright ◽  
M. Udaya Kumar ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Negative Correlation ◽  
Field Experiments ◽  
Carbon Isotope Discrimination ◽  
Genotypic Variation ◽  
Net Assimilation Rate ◽  
Transpiration Efficiency ◽  
Assimilation Rate ◽  
Isotope Discrimination ◽  
Net Assimilation

Genotypic variation in transpiration efficiency (TE) was investigated in a set of cowpea (Vigna unguiculata (L.) Walp.) genotypes grown as isolated plants in pots and under canopy conditions in the field. In the field, plants were grown in mini-lysimeters embedded in the ground around which a crop was grown, to simulate crop canopy condition. Two moisture regimes (100 and 60% of field capacity) were imposed from 30 to 60 days after sowing in both pot and field experiments. TE was determined by measuring transpiration and dry matter (DM) produced by the genotypes during the treatment period. Genotypes differed significantly in DM although the variation in the amount of water transpired (T) was relatively small. The TE ranged from 2.2 to 3.7 g kg–1, representing a significant genotypic and environmental effect on the variation. There was a significant negative correlation (r = –0.77, P<0.01) between TE adjusted for prevailing vapour pressure deficit and carbon isotope discrimination ratio (Δ) across all the experiments and treatments. A significantly positive correlation of TE measured in pot and field experiments suggested a low G x E interaction. There was a negative correlation (r = –0.62, P < 0.01) between T and TE while the correlation of TE with net assimilation rate was non-significant, suggesting that the major cause for variation of TE in cowpea was in general associated with stomatal rather than mesophyll factors. Because of the positive relationship between T and DM, and negative relationship between TE and T, selection for high TE might therefore be associated with reduced T and hence lower DM. However, the present investigation showed a possibility of identifying specific genotypes with a combination of high TE and high net assimilation rate. The genotypes with high TE and high net assimilation rates were able to produce high DM under moisture deficit conditions.

Genetic variation for leaf carbon isotope discrimination and its association with transpiration efficiency in canola (Brassica napus)

2020 ◽  
Vol 47 (4) ◽  
pp. 355
Author(s):  
Shek M. Hossain ◽  
Josette Masle ◽  
Andrew Easton ◽  
Malcolm N. Hunter ◽  
Ian D. Godwin ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Genotypic Variation ◽  
Dry Weight ◽  
Transpiration Efficiency ◽  
Isotope Discrimination ◽  
Leaf Chlorophyll ◽  
Total Dry Weight ◽  
Positive Correlations

Drought is a major constraint to canola production around the world. There is potential for improving crop performance in dry environments by selecting for transpiration efficiency (TE). In this work we investigated TE by studying its genetic association with carbon isotope discrimination (Δ) and other traits, e.g. specific leaf weight (SLW) and leaf chlorophyll content (SPAD). Among the 106 canola genotypes – including open-pollinated, hybrid, inbred types and cytoplasmic variants – tested in the field and glasshouse there was significant genotypic variation for TE, Δ, plant total dry weight, SLW and SPAD. Strong negative correlations were observed between TE and Δ (–0.52 to –0.76). Negative correlations between Δ and SLW or SPAD (–0.43 to –0.78) and smaller but significant positive correlations between TE and SLW or SPAD (0.23 to 0.30) suggested that photosynthetic capacity was, in part, underpinning the variation in TE. A cytoplasmic contribution to genetic variation in TE or Δ in canola was also observed with Triazine tolerant types having low TE and high Δ. This study showed that Δ has great potential for selecting canola germplasm with improved TE.

Genotypic Variation in Relative Growth Rate and Carbon Isotope Discrimination in Sunflower Is Related to Photosynthetic Capacity

1996 ◽  
Vol 23 (2) ◽  
pp. 227 ◽  
Author(s):  
JM Virgona ◽  
DG Farquhar
Keyword(s):  
Growth Rate ◽  
Carbon Isotope ◽  
Relative Growth Rate ◽  
Carbon Isotope Discrimination ◽  
Photosynthetic Capacity ◽  
Genotypic Variation ◽  
Wild Accession ◽  
Assimilation Rate ◽  
Relative Growth ◽  
Isotope Discrimination

A previous study showed that carbon isotope discrimination (Δ) was negatively related to transpiration efficiency (W, the ratio of dry matter accumulation to transpiration) and biomass accumulation amongst sunflower (Helianthus annuus L.) genotypes. Three experiments which explore the physiological basis of relationships between Δ, relative growth rate (RGR) and leaf gas exchange characteristics are reported. Growth was analysed on seven genotypes during the early vegetative stage (up to 31 days after emergence). Carbon isotope discrimination, Δ, W, and photosynthetic CO2 assimilation rate per unit leaf area (A) at ambient concentration of CO2 were measured on plants that made up the final harvest. Six of the seven genotypes were also grown under a low nitrogen (N) regime and harvested at 30 days after emergence. Carbon isotope discrimination was negatively related to relative growth rate (RGR), net assimilation rate (NAR) and photosynthetic rate per unit area, which in turn, were all positively correlated with each other. Genotypic variation inA (51%) was greater than that in leaf conductance, g (32%) and there was no relationship between g and Δ. Under the low N regime, A and g declined by 33 and 12%, respectively, across all genotypes producing a significant rise in A of 1.10. In a second experiment, growth analysis on 13 cultivated forms of H. annuus, a wild accession and a H. argophyllus accession, also showed that there was a positive relationship between RGR and NAR, and that both growth indices were negatively related to Δ. In a further experiment, using 14 genotypes (including the wild accession) there was a highly significant negative correlation (r = -0.85, P < 0.001) between photosynthetic capacity, measured using an oxygen electrode, and Δ. These results indicate that variation in photosynthetic capacity can account for genotypic variation in both Δ and RGR during vegetative growth in sunflower. Hence, faster growing sunflower genotypes have higher rates of photosynthesis and use water more efficiently.

Drought and Pot Size Effects on Transpiration Efficiency and Carbon Isotope Discrimination of Cowpea Accessions and Hybrids

1994 ◽  
Vol 21 (1) ◽  
pp. 23 ◽  
Author(s):  
AM Ismail ◽  
AE Hall ◽  
EA Bray
Keyword(s):  
Leaf Area ◽  
Carbon Isotope ◽  
Size Effects ◽  
Treatment Effects ◽  
Carbon Isotope Discrimination ◽  
Xylem Sap ◽  
Transpiration Efficiency ◽  
Drought Treatment ◽  
Isotope Discrimination ◽  
Pot Size

Carbon isotope discrimination (Δ) has been proposed as a selection criterion for improving adaptation to water-limited environments because it provides a measure of seasonal transpiration efficiency ( WUE). In cowpea (Vigna unguiculata (L.) Walp.), consistent genotypic and drought-induced differences in Δ and WUE have been observed which were correlated as expected based on theory. Values of Δ and WUE for reciprocal hybrids grown under field conditions indicated nuclear inheritance for both characters. High WUE and low Δ were partially dominant under dry field pot conditions, whereas high Δ was partially dominant under natural wet soil conditions. Studies were conducted to test whether differences in rooting environment and xylem ABA levels are responsible for this change in dominance relations. Cowpea accessions and hybrids were grown in the field and subjected to wet or dry treatments with three different pot sizes. The experiment was conducted twice, giving similar results. The dry treatment resulted in decreases in Δ, and increases in WUE and ABA concentration in the xylem sap. Under drought, genotypes with higher WUE had higher xylem ABA, and the hybrids exhibited greater increases in ABA concentration in response to the dry treatment than either parent. Partial confounding was present in that the hybrids had substantial leaf area and water-use rate, and may have experienced greater soil drought in some conditions than some parents, with interacting effects of pot size. Plants in larger pots produced more biomass and leaf area but with no changes in xylem ABA. Concentration of ABA in the xylem sap was correlated with Δ and WUE for genotypic and drought treatment effects but not for pot size effects. Hybrids tended to have higher Δ and lower WUE in relation to mid-parent means when grown in large wet pots than in small dry ones. Changes in hybrid performance with respect to Δ and WUE were more consistent with changes in xylem ABA for drought treatment effects than for pot size effects. Another chemical signal might be involved in mediating pot size effects.

Correlation between carbon isotope discrimination and transpiration efficiency in lines of the C4 species Sorghum bicolor in the glasshouse and the field

1998 ◽  
Vol 25 (1) ◽  
pp. 111 ◽  
Author(s):  
S. Henderson ◽  
S. von Caemmerer ◽  
G.D. Farquhar ◽  
L. Wade ◽  
G. Hammer
Keyword(s):  
Sorghum Bicolor ◽  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Negative Slope ◽  
Environment Interaction ◽  
Transpiration Efficiency ◽  
Isotope Discrimination ◽  
C4 Species ◽  
C3 Species ◽  
The Mean

Transpiration efficiency, W, the ratio of plant carbon produced to water transpired and carbon isotope discrimination of leaf dry matter, Δd, were measured together on 30 lines of the C4 species, Sorghum bicolor, in the glasshouse and on eight lines grown in the field. In the glasshouse, the mean W observed was 4.9 mmol C mol-1 H2O and the range was 0.8 mmol C mol -1 H2O. The mean Δd was 3.0 and the observed range was 0.4‰. In the field, the mean W was lower at 2.8 mmol C mol-1 H2O and the mean Δd was 4.6‰. Significant positive correlations between W and Δd were observed for plants grown in the glasshouse and in the field. The observed correlations were consistent with theory, opposite to those for C3 species, and showed that variation in Δd was an integrated measure of long-term variation in the ratio of intercellular to ambient CO2 partial pressure, pi/pa. Detailed gas exchange measurements of carbon isotope discrimination during CO2 uptake, ΔA, and pi/pa were made on leaves of eight S. bicolorlines. The observed relationship between ΔA and pi/pa was linear with a negative slope of 3.7‰ in ΔA for a unit change in pi/pa. The slope of this linear relationship between ΔA and pi/pa in C4 species is dependent on the leakiness of the CO2 concentrating mechanism of the C4 pathway. We estimated the leakiness (defined as the fraction of CO2 released in the bundle sheath by C4 acid decarboxylations, which is lost by leakage) to be 0.2. We conclude that, although variation in Δd observed in the 30 lines of S. bicolor is smaller than that commonly observed in C3 species, it also reflects variation in transpiration efficiency, W. Among the eight lines examined in detail and in the environments used, there was considerable genotype × environment interaction.

Carbon Isotope Discrimination and Transpiration Efficiency in Common Bean

Crop Science ◽  
1991 ◽  
Vol 31 (6) ◽  
pp. 1611-1615 ◽  
Author(s):  
James R. Ehleringer ◽  
Stephen Klasen ◽  
Creed Clayton ◽  
Dorothy Sherrill ◽  
Mindy Fuller‐Holbrook ◽  
...  
Keyword(s):  
Common Bean ◽  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Transpiration Efficiency ◽  
Isotope Discrimination
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