Relationships of stable carbon isotopes, plant water potential and growth: an approach to asses water use efficiency and growth strategies of dry land agroforestry species

In the present study, we evaluated the seedling growth, water status and signature of stable carbon isotopes in C3 perennial species exposed to natural phytochemicals. Three perennial species, cocksfoot (Dactylis glomerata), perennial ryegrass (Lolium perenne) and common sorrel (Rumex acetosa), were grown for 30 days in perlite, watered with Hoagland solution and exposed to the phytochemicals benzoxazolin-2(3H)-one (BOA) and cinnamic acid (CA) at 0, 0.1, 0.5, 1.0 and 1.5 mM concentrations. BOA markedly decreased the leaf and root fresh weights of D. glomerata and L. perenne in a concentration-dependent manner. The leaf fresh weight (LFW) of plants treated with CA (1.5 mM) was similarly affected by showing a decrease of LFW, being the lowest in L. perenne (56%) followed by D. glomerata (46%). The relative water contents of L. perenne, D. glomerata and R. acetosa were decreased while maximum RWC reduction was observed in L. perenne. Carbon isotope discrimination in L. perenne, D. glomerata and R. acetosa were reduced following treatment with BOA and CA at 1.5 mM. BOA at 1.5 mM decreased the ratio of intercellular to ambient CO2 concentration relative to control in L. perenne, D. glomerata and R. acetosa. There was an increase in water-use efficiency in L. perenne, D. glomerata and R. acetosa after treatment with BOA and CA. The dry weight of plants treated with CA (1.5 mM) showed different patterns of variation, being lowest in L. perenne (33%) followed by D. glomerata (3%) and R. acetosa (2%). Phytotoxicity was higher for the perennial grass than for the perennial broadleaf. These results clearly demonstrate a widespread occurrence of phytotoxicity among the three species, their tolerance and relationship between carbon isotope discrimination and intrinsic water-use efficiency.

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Stable Carbon Isotopes in Zea mays

10.1101/414789 ◽

2018 ◽

Author(s):

Robert J. Twohey ◽

Lucas M. Roberts ◽

Anthony J. Studer

Keyword(s):

Zea Mays ◽

Carbon Isotopes ◽

Water Use ◽

Stable Carbon Isotopes ◽

Carbon Fixation ◽

Isotope Composition ◽

Stable Carbon Isotope ◽

Climate Change Scenarios ◽

Transpiration Efficiency ◽

Stable Carbon

SummaryThe increasing demand for food production and predicted climate change scenarios highlight the need for improvements in crop sustainability. The efficient use of water will become increasingly important for rainfed agricultural crops even in fertile regions that have historically received ample precipitation. Improvements in water-use efficiency in Zea mays have been limited, and warrants a renewed effort aided by molecular breeding approaches. Progress has been constrained by the difficulty of measuring water-use in a field environment. The stable carbon isotope composition (δ13C) of the leaf has been proposed as an integrated signature of carbon fixation with a link to stomatal conductance. However, additional factors affecting leaf δ13C exist, and a limited number of studies have explored this trait in Z. mays. Here we present an extensive characterization of leaf δ13C in Z. mays. Significant variation in leaf δ13C exists across diverse lines of Z. mays, which we show to be heritable across several environments.Furthermore, we examine temporal and spatial variation in leaf δ13C to determine the optimum sampling time to maximize the use of leaf δ13C as a trait. Finally, our results demonstrate the relationship between transpiration and leaf δ13C in the field and the greenhouse. Decreasing transpiration and soil moisture are associated with decreasing leaf δ13C. Taken together these results outline a strategy for using leaf δ13C and reveal its usefulness as a measure of transpiration efficiency under well-watered conditions rather than a predictor of performance under drought.Significance StatementThis study identifies sources of variation in stable carbon isotopes of maize leaves and establishes the framework for connecting leaf δ13C and transpiration efficiency.

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