Modelling Stomatal Responses to Environment in Macadamia integrifolia

1991 ◽  
Vol 18 (6) ◽  
pp. 649 ◽  
Author(s):  
J Lloyd
Keyword(s):  
Stomatal Closure ◽  
Co2 Assimilation ◽  
Leaf Temperature ◽  
Least Squares Regression ◽  
Gain Ratio ◽  
Humidity Response ◽  
Macadamia Integrifolia ◽  
Stomatal Responses ◽  
Simple Equations ◽  
The Relationship

Gas exchange measurements were made of photosynthetic and stomatal responses of Macadamia integrifolia under controlled conditions. Test leaves were subjected to a range of temperatures, humidities and photon irradiances. When stomatal responses to humidity were plotted as a function of vapour mol fraction difference (D) a similar curvilinear response was observed at all temperatures and at photon irradiances of 200 and 1500 μmol quanta m-2 s-1. By contrast, when expressed as a function of relative humidity, different slopes in the humidity response were observed, and at high photon irradiances, stomatal conductances (gs) appeared to have an optimum temperature below 15�C. Simple equations to quantify responses to leaf temperature (TI) and D were developed, the best of which was gs = [1-k1(1-[Tl/Topt)]/k2√D, where Topt is the leaf temperature at which maximal stomatal opening is observed and k1 and k2 are constants fitted by non-linear least squares regression analysis. Calculation of the gain ratio of CO2 assimilation (A) to transpiration (E) (δA/δE) was complicated by effects of D on the relationship between A and leaf intercellular mol fraction of CO2 (CI). Calculation of δA/δE using A/CI relationships derived by varying external CO2 mol fraction at constant D showed the gain ratio to be virtually constant (1.5 mmol mol-1) across a range of leaf temperatures and vapour mol fraction differences but, when calculated directly from the relationship between A and gs, a decrease in δA/δE with D was observed. Macadamia leaves have heavily sclerified bundle sheath extensions and it is considered that this dependence was an artefact due to non-uniform stomatal closure in response to increasing D. It is shown that, at any given temperature, a stomatal response of the form gsD-1/2 gives rise to an approximately constant δA/δE.

scholarly journals Changes in Agronomic and Physiological Traits of Sugarcane Grown with Saline Irrigation Water

Agronomy ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 722
Author(s):  
Kenta Watanabe ◽  
Hiroo Takaragawa ◽  
Masami Ueno ◽  
Yoshinobu Kawamitsu
Keyword(s):  
Salt Concentration ◽  
Irrigation Water ◽  
Stomatal Closure ◽  
Co2 Assimilation ◽  
Physiological Traits ◽  
Sugar Concentration ◽  
Saline Irrigation ◽  
Saccharum Spp ◽  
The Relationship ◽  
Harmful Effects

In Japan, the highest salt concentration in irrigation water for sugarcane cultivation has been reported to be above 2500 mg L−1, which may cause harmful effects to the crops; however, little information is available on the relationship between the salinity of irrigation water and sugarcane. To investigate its effects on agronomic and physiological traits, a Japanese cultivar, Saccharum spp cv. NiF8, was grown with 0, 200, 500, 1000, 2000, and 3000 mg NaCl L−1 under pot conditions. The treatments significantly lowered leaf area; however, NaCl levels up to 500 mg L−1 did not greatly reduce culm weight and juice sugar concentration. These traits were impaired when the tested cultivar was grown with 1000 mg NaCl L−1 or higher, indicating that salt concentration is desired to be lower than 1000 mg L−1. CO2 assimilation rate was inhibited mainly due to stomatal closure caused by salt stress. The treatments significantly altered Na+, Cl−, and K+ concentrations in juice but not those in leaf, suggesting that juice analysis is an effective method to estimate its salinization status. Culm weight and juice sugar concentration were severely affected as juice conductivity exceeded 900 mS m−1; thereby, sugarcane plants of NiF8 possessing conductivity above this level could be considered salt-stressed where water salinity is a concern.

Elevated CO2 increases the leaf temperature of two glasshouse-grown C4 grasses

2002 ◽  
Vol 29 (12) ◽  
pp. 1377 ◽  
Author(s):  
Katharina Siebke ◽  
Oula Ghannoum ◽  
Jann P. Conroy ◽  
Susanne von Caemmerer
Keyword(s):  
Gas Exchange ◽  
Elevated Co2 ◽  
Leaf Gas Exchange ◽  
Stomatal Closure ◽  
Co2 Assimilation ◽  
High Irradiance ◽  
Leaf Temperature ◽  
C4 Grasses ◽  
Co2 Partial Pressure ◽  
The Difference

This study investigates the effect of elevated CO2 partial pressure (pCO2)-induced stomatal closure on leaf temperature and gas exchange of C4 grasses. Two native Australian C4 grasses, Astrebla lappacea (Lindl.) Domin and Bothriochloa bladhii Kuntze, were grown at three different pCO2 (35, 70 and 120 Pa) in three matched, temperature-controlled glasshouse compartments. The difference between leaf and air temperature (ΔT) was monitored diurnally with thermocouples. ΔT increased with both step-increases of ambient pCO2. Average noon leaf temperature increased by 0.4 and 0.3°C for A. lappacea with the 35–70 and 70–120 Pa steps of pCO2 elevation, respectively. For B. bladhii, the increases were 0.5°C for both pCO2 steps. ΔT was strongly dependent on irradiance, pCO2 and air humidity. Leaf gas exchange was measured at constant temperature and high irradiance at the three growth pCO2. Under these conditions, CO2 assimilation saturated at 70 Pa, while stomatal conductance decreased by the same extent (0.58-fold) with both step-increases in pCO2, suggesting that whole-plant water use efficiency of C4 grasses would increase beyond a doubling of ambient pCO2. The ratio of intercellular to ambient pCO2 was not affected by short- or long-term doubling or near-tripling of pCO2, in either C4 species when measured under standard conditions.

scholarly journals Manganese toxicity disrupts indole acetic acid homeostasis and suppresses the CO2 assimilation reaction in rice leaves

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daisuke Takagi ◽  
Keiki Ishiyama ◽  
Mao Suganami ◽  
Tomokazu Ushijima ◽  
Takeshi Fujii ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Indole Acetic Acid ◽  
Molecular Mechanisms ◽  
Stomatal Closure ◽  
Co2 Assimilation ◽  
Terrestrial Plants ◽  
Mn Toxicity ◽  
Growth Defects ◽  
The Relationship ◽  
Excessive Accumulation

AbstractDespite the essentiality of Mn in terrestrial plants, its excessive accumulation in plant tissues can cause growth defects, known as Mn toxicity. Mn toxicity can be classified into apoplastic and symplastic types depending on its onset. Symplastic Mn toxicity is hypothesised to be more critical for growth defects. However, details of the relationship between growth defects and symplastic Mn toxicity remain elusive. In this study, we aimed to elucidate the molecular mechanisms underlying symplastic Mn toxicity in rice plants. We found that under excess Mn conditions, CO2 assimilation was inhibited by stomatal closure, and both carbon anabolic and catabolic activities were decreased. In addition to stomatal dysfunction, stomatal and leaf anatomical development were also altered by excess Mn accumulation. Furthermore, indole acetic acid (IAA) concentration was decreased, and auxin-responsive gene expression analyses showed IAA-deficient symptoms in leaves due to excess Mn accumulation. These results suggest that excessive Mn accumulation causes IAA deficiency, and low IAA concentrations suppress plant growth by suppressing stomatal opening and leaf anatomical development for efficient CO2 assimilation in leaves.

scholarly journals Smart Glass Impacts Stomatal Sensitivity of Greenhouse Capsicum Through Altered Light

2021 ◽  
Author(s):  
Chenchen Zhao ◽  
Sachin Chavan ◽  
Xin He ◽  
Meixue Zhou ◽  
Christopher I Cazzonelli ◽  
...  
Keyword(s):  
Stomatal Closure ◽  
Co2 Assimilation ◽  
Short Wave ◽  
Light Transmittance ◽  
Wave Radiation ◽  
High Tech ◽  
Stomatal Responses ◽  
Optical Films ◽  
Leaf Water Loss ◽  
Use Efficiency

Abstract Optical films that alter light transmittance may reduce energy consumption in high-tech greenhouses, but their impact on crop physiology remains unclear. We compared the stomatal responses of Capsicum plants grown hydroponically under control glass (70% diffuse light) or smart glass (SG) film ULR-80, which blocked >50% of short-wave radiation and ~9% of photosynthetically active radiation (PAR). SG had no significant effects on steady-state (gs) or maximal (gmax) stomatal conductance. In contrast, SG reduced stomatal pore size and sensitivity to exogenous ABA thereby increasing rates of leaf water loss, guard cell K + and Cl - efflux, and Ca 2+ influx. SG induced faster stomatal closing and opening rates on transition between low (100 µmol m -2 s -1) and high PAR (1500 µmol m -2 s -1), which compromised water use efficiency relative to control plants. The fraction of blue light (0% or 10%) did not affect gs in either treatment. Increased expression of stomatal closure and photoreceptor genes in epidermal peels of SG plants is consistent with fast stomatal responses to light changes. In conclusion, stomatal responses of Capsicum to SG were more affected by changes in light intensity than spectral quality, and re-engineering of the SG should maximize PAR transmission, and hence CO2 assimilation.

scholarly journals Concentration matters: different stomatal CO2-responses at sub-ambient and above-ambient CO2 levels

2021 ◽  
Author(s):  
Hanna Hõrak ◽  
Kaspar Koolmeister ◽  
Ebe Merilo ◽  
Hannes Kollist
Keyword(s):  
Guard Cell ◽  
Stomatal Closure ◽  
Cell Signalling ◽  
Anion Channel ◽  
Leaf Temperature ◽  
Signalling Pathways ◽  
Stomatal Responses ◽  
Slow Type ◽  
Ambient Concentrations ◽  
Ambient Co2

Stomatal pores, formed of paired guard cells, mediate CO2 uptake for photosynthesis and water loss via transpiration in plants. Globally rising atmospheric CO2 concentration triggers stomatal closure, contributing to increased leaf temperature and reduced nutrient uptake due to lower transpiration rate. Hence, it is important to understand the signalling pathways that control elevated CO2-induced stomatal closure to identify targets for breeding climate-ready crops. CO2-induced stomatal closure can be studied by increasing CO2 concentration from ambient to above-ambient concentrations, or elevation of CO2 levels from sub-ambient to above-ambient. Previous experiments comparing ferns with angiosperms suggested that stomatal responses to CO2 may be different, when changing CO2 levels in the sub-ambient or above-ambient ranges. Here, we set out to test this by comparing CO2-induced stomatal closure in key guard cell signalling mutants in response to CO2 elevation from 100 to 400 ppm or 400 to 800 ppm. We show that signalling components that contribute to CO2-induced stomatal closure are different in the sub-ambient and above-ambient CO2 levels, with guard cell slow-type anion channel SLAC1 involved mainly in above-ambient CO2-induced stomatal closure.

scholarly journals Manganese toxicity disrupts indole acetic acid homeostasis and suppresses CO2 assimilation reaction in rice plants

2021 ◽  
Author(s):  
Daisuke Takagi ◽  
Keiki Ishiyama ◽  
Mao Suganami ◽  
Tomokazu Ushijima ◽  
Takeshi Fujii ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Indole Acetic Acid ◽  
Molecular Mechanisms ◽  
Stomatal Closure ◽  
Co2 Assimilation ◽  
Terrestrial Plants ◽  
Mn Toxicity ◽  
Rice Plants ◽  
Growth Defects ◽  
The Relationship

Despite the essentiality of Mn in terrestrial plants, its excessive accumulation in plant tissues causes growth defects, known as Mn toxicity. Mn toxicity can be divided into apoplastic and symplastic types depending on its onset. For growth defects, symplastic rather than apoplastic Mn toxicity is hypothesised to be more critical. However, details of the relationship between growth defects and symplastic Mn toxicity remains elusive. In this study, we aimed to elucidate the molecular mechanisms of symplastic Mn toxicity in rice plants. We found that under excess Mn conditions, CO2 assimilation was inhibited by stomatal closure, and both carbon anabolic and catabolic activities were decreased. In addition to stomatal dysfunction, stomatal and leaf anatomical development were also altered by excess Mn accumulation. Furthermore, the indole acetic acid (IAA) concentration was decreased, and auxin-responsive gene expression analyses showed IAA-deficient symptoms in leaves due to excess Mn accumulation. These results suggest that excessive Mn accumulation causes IAA deficiency, and low IAA concentrations suppress plant growth by suppressing stomatal opening and leaf anatomical development for efficient CO2 assimilation in leaves.

The impact of executives’ perceptions of environmental threats and organizational slack on innovation strategies

2016 ◽  
Vol 7 (2) ◽  
pp. 216-230 ◽  
Author(s):  
Chengyuan Wang ◽  
Biao Luo ◽  
Yong Liu ◽  
Zhengyun Wei
Keyword(s):  
Cognitive Theory ◽  
Environmental Changes ◽  
Ordinary Least Squares ◽  
Organizational Slack ◽  
Least Squares Regression ◽  
Content Type ◽  
Environmental Threats ◽  
Innovation Strategies ◽  
The Impact ◽  
The Relationship

Purpose The paper aims to study the relationship between executives’ perceptions of environmental threats and innovation strategies and investigate the moderating effect of contextual factor (i.e. organizational slack) on such relations. It proposes a dualistic relationship between executives’ perceptions of environmental threats and innovation strategies, in which different perceptions of environmental threats will lead to corresponding innovation strategies, and dyadic organizational slack can promote such processes. Design/methodology/approach The paper is based on a survey with 163 valid questionnaires, which were all completed by executives. Hierarchical ordinary least-squares regression analysis is used to test the hypotheses proposed in this paper. Findings The paper provides empirical insights about that executives tend to choose exploratory innovation when they perceive environmental changes as likely loss threats, yet adopt exploitative innovation when perceiving control-reducing threats. Furthermore, unabsorbed slack (e.g. financial redundancy) positively moderates both relationships, while absorbed slack (e.g. operational redundancy) merely positively influences the relationship between the perception of control-reducing threats and exploitative innovation. Originality/value The paper bridges the gap between organizational innovation and cognitive theory by proposing a dualistic relationship between executives’ perceptions of environmental threats and innovation strategies. The paper further enriches innovation studies by jointly considering both subjective and objective influence factors of innovation and argues that organizational slack can moderate such dualistic relationship.

scholarly journals Retrospectives: The Introduction of the Cobb–Douglas Regression

2012 ◽  
Vol 26 (2) ◽  
pp. 223-236 ◽  
Author(s):  
Jeff Biddle
Keyword(s):  
Time Series Data ◽  
Series Data ◽  
Mathematical Representation ◽  
Least Squares Regression ◽  
Empirical Measures ◽  
Stable Relationship ◽  
Initial Application ◽  
Economic Association ◽  
The Relationship ◽  
Theory Of Production

At the 1927 meetings of the American Economic Association, Paul Douglas presented a paper entitled “A Theory of Production,” which he had coauthored with Charles Cobb. The paper proposed the now familiar Cobb–Douglas function as a mathematical representation of the relationship between capital, labor, and output. The paper's innovation, however, was not the function itself, which had originally been proposed by Knut Wicksell, but the use of the function as the basis of a statistical procedure for estimating the relationship between inputs and output. The paper's least squares regression of the log of the output-to-capital ratio in manufacturing on the log of the labor-to-capital ratio—the first Cobb–Douglas regression—was a realization of Douglas's innovative vision that a stable relationship between empirical measures of inputs and outputs could be discovered through statistical analysis, and that this stable relationship could cast light on important questions of economic theory and policy. This essay provides an account of the introduction of the Cobb–Douglas regression: its roots in Douglas's own work and in trends in economics in the 1920s, its initial application to time series data in the 1927 paper and Douglas's 1934 book The Theory of Wages, and the early reactions of economists to this new empirical tool.

scholarly journals Intraspecific Variation in Maximum Ingested Food Size and Body Mass in Varecia rubra and Propithecus coquereli

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Adam Hartstone-Rose ◽  
Jonathan M. G. Perry
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Individual Variation ◽  
Size Variation ◽  
Maximum Size ◽  
Least Squares Regression ◽  
Scaling Relationship ◽  
Varecia Rubra ◽  
Food Size ◽  
The Relationship

In a recent study, we quantified the scaling of ingested food size (Vb )—the maximum size at which an animal consistently ingests food whole—and found that Vb scaled isometrically between species of captive strepsirrhines. The current study examines the relationship between Vb and body size within species with a focus on the frugivorous Varecia rubra and the folivorous Propithecus coquereli. We found no overlap in Vb between the species (all V. rubra ingested larger pieces of food relative to those eaten by P. coquereli), and least-squares regression of Vb and three different measures of body mass showed no scaling relationship within each species. We believe that this lack of relationship results from the relatively narrow intraspecific body size variation and seemingly patternless individual variation in Vb within species and take this study as further evidence that general scaling questions are best examined interspecifically rather than intraspecifically.

Audit committee characteristics and the moderating effect of Malaysian code of corporate governance on IPO liquidity

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Amal Mohammed Al-Masawa ◽  
Rasidah Mohd-Rashid ◽  
Hamdan Amer Al-Jaifi ◽  
Shaker Dahan Al-Duais
Keyword(s):  
Corporate Governance ◽  
Initial Public Offerings ◽  
Audit Committee ◽  
Ordinary Least Squares ◽  
Moderating Effect ◽  
Least Squares Regression ◽  
Content Type ◽  
Code Of Corporate Governance ◽  
The Impact ◽  
The Relationship

Purpose This study aims to investigate the link between audit committee characteristics and the liquidity of initial public offerings (IPOs) in Malaysia, which is an emerging economy in Southeast Asia. Another purpose of this study is to examine the moderating effect of the revised Malaysian code of corporate governance (MCCG) on the link between audit committee characteristics and IPO liquidity. Design/methodology/approach The final sample consists of 304 Malaysian IPOs listed in 2002–2017. This study uses ordinary least squares regression method to analyse the data. To confirm this study’s findings, a hierarchical or four-stage regression analysis is used to compare the t-values of the main and moderate regression models. Findings The findings show that audit committee characteristics (size and director independence) have a positive and significant relationship with IPO liquidity. Also, the revised MCCG positively moderates the relationship between audit committee characteristics and IPO liquidity. Research limitations/implications This study’s findings indicate that companies with higher audit committee independence have a more effective monitoring mechanism that mitigates information asymmetry, thus reducing adverse selection issues during share trading. Practical implications Policymakers could use the results of this study in developing policies for IPO liquidity improvements. Additionally, the findings are useful for traders and investors in their investment decision-making. For companies, the findings highlight the crucial role of the audit committee as part of the control system that monitors corporate governance. Originality/value To the authors’ knowledge, this work is a pioneering study in the context of a developing country, specifically Malaysia that investigates the impact of audit committee characteristics on IPO liquidity. Previously, the link between corporate governance and IPO liquidity had not been investigated in Malaysia. This study also contributes to the IPO literature by providing empirical evidence regarding the moderating effect of the revised MCCG on the relationship between audit committee characteristics and IPO liquidity.

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