David W. Lawlor

Formerly Rothamsted Research · Plant Sciences

Advances have been recently made in the breeding and characterization of three major legume crops of the semiarid tropics, chickpea, pigeon pea, and groundnut. However, other wild-growing legumes, called "orphan legumes," with potential as crops, but are not yet cultivated would benefit from further attention. This review considers the domesticatio...

Advances have been recently made in the breeding and characterization of three major legume crops of the semiarid tropics, chickpea, pigeon pea, and groundnut. However, other wild‐growing legumes, called “orphan legumes,” with potential as crops, but are not yet cultivated would benefit from further attention. This review considers the domesticatio...

Marama Bean (Tylosema esculentum): A Review of Morphological and Physiological Adaptations to Environment, and Crop Potential. David W Lawlor Formerly Rothamsted Research, Harpenden, Herts, AL5 2AQ, UK. https://www.researchgate.net Abstract Marama is a leguminous, tuber-forming perennial, adapted to dry, deep sands lacking organic matter and nutrie...

Marama Bean (Tylosema esculentum): A Review of Morphological and Physiological Adaptations to Environment, and Crop Potential. David W Lawlor (Formerly Rothamsted Research, Harpenden, Herts, AL5 2AQ, UK. (https://www.researchgate.net) Marama is a leguminous perennial, which forms very large underground tubers, from the hot, semi-desert areas aro...

Background The trehalose (Tre) pathway has strong effects on growth and development in plants through regulation of carbon metabolism. Altering either Tre or trehalose 6-phosphate (T6P) can improve growth and productivity of plants as observed under different water availability. As yet, there are no reports of the effects of modification of Tre orT...

A review of the publication evaluating its contribution to the literature addressing the effects of changes in environment - temperature and CO2 principally - on plants and implications for crop production.

A review of the scientific basis of crop production with changing environment and climate.

To study the direct effects of photosynthesis on allocation of biomass by altering photosynthesis without altering leaf N or nitrate content, phosphoribulokinase (PRK) activity was decreased in transgenic tobacco (Nicotiana tabacum.) with an inverted tobacco PRK cDNA and plants were grown at different N levels (0.4 and 5 ITIMNH4NO3). The activation...

This detailed review of the factors determining productivity of crops provides a summary of the large literature, over many years, which is accessible to a wide range of scientists in agriculture, plant physiology and plant biochemistry. It is also a valuable introduction to the topic for students. It is In Memory of Professor Lubos Natr, Charles U...

Durum wheat is susceptible to terminal drought which can greatly decrease grain yield. Breeding to improve crop yield is hampered by inadequate knowledge of how the physiological and metabolic changes caused by drought are related to gene expression. To gain better insight into mechanisms defining resistance to water stress we studied the physiolog...

Considerable interest has been evoked by the analysis of the regulatory pathway in carbohydrate metabolism and cell growth involving the non-reducing disaccharide trehalose (TRE). TRE is at small concentrations in mesophytes such as Arabidopsis thaliana and Triticum aestivum, excluding a role in osmoregulation once suggested for it. Studies of TRE...

The southern part of Mozambique is vulnerable to drought, affecting the country's food production, and thus requires more drought-tolerant crops. Four local cowpea landraces, Massava nhassenje, Timbawene moteado, Namarua and Tete-2, which are currently widely used by local Mozambican farmers, were evaluated for their drought tolerance with the aim...

In a context of understanding the physiological mechanisms and cultivar traits which could improve durum wheat (Triticum durum) yield in water limited conditions, the paper focuses on the contribution of stored assimilates to grain growth and yield. A conceptual model describing the different fluxes of assimilate during the grain filling period is...

Fully drought-resistant crop plants would be beneficial, but selection breeding has not produced them. Genetic modification of species by introduction of very many genes is claimed, predominantly, to have given drought resistance. This review analyses the physiological responses of genetically modified (GM) plants to water deficits, the mechanisms,...

A critical review of a multi-author collection of review papers on predominantly genomic aspects poorly related to the problem of plant responses to environment

Agricultural crop production in Africa is dominated by subsistence farming limited by inadequate resources on nutrient- and humus-poor soils, with poor water holding capacity. Rainfall is often low and erratic, with high temperatures. Yields are very small, variable, and not increasing; even small gains would greatly improve people’s welfare. The g...

Understanding of how plants respond to their environment, particularly to extreme conditions to which their metabolisms are not adapted, is advancing on many fronts. An enormous matrix of plant and environmental factors exists from which mechanisms and assessments of quantitative responses must be developed if further progress in understanding how...

Background Water deficit (WD) decreases photosynthetic rate (A) via decreased stomatal conductance to CO2 (gs) and photosynthetic metabolic potential (Apot). The relative importance of gs and Apot, and how they are affected by WD, are reviewed with respect to light intensity and to experimental approaches. Scope and Conclusions With progressive WD...

Agricultural crop production in Africa is dominated by subsistence farming limited by inadequate resources on nutrient-and humus-poor soils, with poor water holding capacity. Rainfall is often low and erratic, with high temperatures. Yields are very small, variable, and not increasing; even small gains would greatly improve people's welfare. The gr...

In long-term field experiments, during consecutive years, microswards of subterranean clover were irrigated to minimise water deficits or subjected to progressively increasing drought over 30 days. Both leaf water potential and relative water content steadily decreased during the experiments. Plants affected by drought grew more slowly and photosyn...

In sunflower (Helianthus annuus L.) grown under controlled conditions and subjected to drought by withholding watering, net photosynthetic rate (P N) and stomatal conductance (g s) of attached leaves decreased as leaf water potential (Ψw) declined from −0.3 to −2.9 MPa. Although g s decreased over the whole range of Ψw, nearly constant values in th...

Sugar beet were grown for short periods with different amounts of moisture in the soil and air. Growing plants in wet soil (23 % moisture on dry weight) compared with dry soil (15% moisture) increased growth of the shoots and roots and plant dry weights by 15% in young plants and 10% in mature plants. Growing plants in wet air containing 10.9 g m-3...

Conference held at Rothamsted Research, Harpenden UK, 12-13 November 2008

Rising atmospheric [CO2] can increase photosynthesis and yield of crops but rising temperature could increase transpiration more strongly. Water use efficiency (WUE, total dry matter or yield produced per unit of water used) is the result of these two intensely intertwined processes. This paper considers the factors determining WUE in crops and mod...

The growth and water transport of wheat plants was measured with the root system divided into two equal parts and grown in solutions of different osmotic potential. Growth of roots decreased with decrease in osmotic potential and stopped at -10 bar, but solutions of high osmotic potential, available to part of the root system, did not significantly...

Winter wheat (Triticum aestivum L., cv. Mercia) was grown in chambers under light and temperature conditions similar to the UK field environment for the 1990/1991 growing season at two levels each of atmospheric CO2 concentration (seasonal means: 361 and 692 μmol mol−1), temperature (tracking ambient and ambient +4°C) and nitrogen application (equi...

Only a small proportion of elevated CO2 studies on crops have taken place in the field. They generally confirm results obtained in controlled environments: CO2 increases photosynthesis, dry matter production and yield, substantially in C3 species, but less in C4, it decreases stomatal conductance and transpiration in C3 and C4 species and greatly i...

Winter wheat (Triticum aestivum L., cv. Mercia) was grown at two different atmospheric CO2 concentrations (350 and 700 μmol mol−1), two temperatures [ambient temperature (i.e. tracking the open air) and ambient +4°C] and two rates of nitrogen supply (equivalent to 489 kg ha−1 and 87 kg ha−1). Leaves grown at 700 μmol mol−1 CO2 had slightly greater...

Wheat plants were cultivated under growth regimes combining two temperatures (ambient and 4°C above ambient temperature) with two concentrations or carbon dioxide (350 and 700 μmol mol) and two nitrogen fertilizer applications (high and low). The aim of this study was to define any changes in the acyl lipid composition of wheat grains which could r...

Winter wheat (Triticum aestivum L., ev. Mercia) was grown in a controlled-environment facility at two CO2 concentrations (targets 350 and 700 μmol mol−1), and two temperature regimes (tracking ambient and ambient + 4°C). Observations of phenology, canopy growth, dry matter production and grain yield were used to test the ARCWHEAT1 simulation model....

The effects of extreme phosphate (Pi) deficiency during growth on the contents of adenylates and pyridine nucleotides and the in vivo photochemical activity of photosystem II (PSII) were determined in leaves of Helianthus annuus and Zea mays grown under controlled environmental conditions. Phosphate deficiency decreased the amounts of ATP and ADP p...

Abstract Carbon fluxes in photosynthesis and photorespiration of water stressed leaves have been analysed in a steady state model based on the ribulose diphosphate carboxylase (RuDP carboxylase) and RuDP oxygenase enzyme activities and the CO2 and O2 concentrations in the leaf. Agreement between predicted and observed photorespiration (Lawlor & Foc...

Marama bean, Tylosema esculentum, is a tuberous legume native to the Kalahari region of Southern Africa where it grows under high temperatures (typical daily max 37 degrees C during growing season) and radiation (frequently in excess of 2000 micromol m(-2) s(-1)) in sandy soils with low rainfall. These conditions might be expected to select for inc...

Study investigate effect of ambient (350 μmol -1) and elevated (700 μmol -1) CO 2 under water stress conditions on phosphoribulokinase deficient transgenic tobacco plants (C8) generated through antisense technique and found to have only 5% phosphoribulokinase activity (referred to as transformants) as compared to wild type (Bin-19) on growth, net C...

Plant species differ in response to nitrogen (N) supply, depending on environment. Mechanisms of NH4 + and NO3 − uptake, reduction of NO3 − to NH4 +, and NH4 + incorporation into amino acids, depend on light energy which drives photosynthesis, providing reductant, ATP and carbohydrates. Amino acids are used in protein synthesis, which is the basic...

Pre-industrial global atmospheric carbon dioxide (CO2) concentration (Ca), was ca. 280 µl l−1, is now 376 µl l−1, and may be 700 µl l−1 by 2100. Temperature is now ca. 0.6°C greater than pre-industrially, and may be ca. 4°C greater by 2100. Warming is decreasing frost, snow and ice cover. Rain may increase in some areas, particularly high latitudes...

Exponential rise in the atmospheric carbon dioxide (CO2) concentration anthropogenically has aroused interest to characterize the possible response of crop plants to the elevated carbon dioxide in future. Open Top Chamber (OTC) and Free Air Carbon Dioxide (CO2) Enrichment (FACE) technologies were developed to study the crop responses. Study reveale...

Photosynthesis is the basis of crop production and it is considered that there is need to improve the metabolic processes responsible, in order to increase the rate of carbon dioxide assimilation, if crop production and economic yields are to be increased. This analysis addresses how the mechanisms may be altered to achieve the aim.

Summary • Here, the contribution of stomatal and nonstomatal factors to photosynthetic inhibition under water stress in four tropical C 4 grasses was investigated ( Panicum coloratum , Bothriochloa bladhii , Cenchrus ciliaris and Astrebla lappacea ). • Plants were grown in well watered soil, and then the effects of soil drying were measured on leaf...

Global climate, and that of Northern Europe, has changed since the start of the industrial revolution, ca 1750. Atmospheric carbon dioxide (CO2) concentrations (Ca) have risen from 280 microliter per litre then, to 360microliter per litre now, and will continue to rise probably to 700 (range 560-1000) microliter per litre by 2100. Global temperatur...

Four mutants with delayed leaf senescence were selected from seed of durum wheat mutagenized with ethylmethane sulphonate. Changes in net photosynthetic rate, efficiency of photosystem II and chlorophyll concentration during the maturation and senescence of the flag leaves of both mutant and parental plants were determined under glasshouse conditio...

To quantify the importance of the Calvin cycle enzyme phosphoribulokinase (PRK) in photosynthesis and to perturb photosynthesis without large direct reductions in leaf protein content, tobacco plants (Nicotiana tabacum L.) were transformed with an inverted cDNA encoding tobacco PRK. A population of plants expressing antisense RNA and a range of PRK...

SYNOPSIS. Man has been engaged in the genetic manipulation of crop plants for millennia. At its most elemental level, plant genetic manipulation has three requirements: (1) a source of genetic variability that can be utilized for plant improvement; (2) methods for propagating desirable plant genotypes; and (3) strategies for the transfer and select...

Photosynthetic responses of sunflower plants grown for 52 d in ambient and elevated CO2 (A=350 or E=700 µmol mol–1, respectively) and subjected to no (control), mild or severe water deficits after 45 d were analysed to determine if E modifies responses to water deficiency. Relative water content, leaf water potential (Ψw) and osmotic potential decr...

Decreasing relative water content (RWC) of leaves progressively decreases stomatal conductance (gs), slowing CO2 assimilation (A) which eventually stops, after which CO2 is evolved. In some studies, photosynthetic potential (Apot), measured under saturating CO2, is unaffected by a small loss of RWC but becomes progressively more inhibited, and less...

Improved understanding of crop production systems in relation to N-supply has come from a knowledge of basic plant biochemistry and physiology. Gene expression leads to protein synthesis and the formation of metabolic systems; the ensuing metabolism determines the capacity for growth, development and yield production. This constitutes the genetic p...

Improved understanding of crop production systems in relation to N‐supply has come from a knowledge of basic plant biochemistry and physiology. Gene expression leads to protein synthesis and the formation of metabolic systems; the ensuing metabolism determines the capacity for growth, development and yield production. This constitutes the genetic p...

Experimental studies on CO2 assimilation of mesophytic C3 plants in relation to relative water content (RWC) are discussed. Decreasing RWC slows the actual rate of photosynthetic CO2 assimilation (A) and decreases the potential rate (Apot). Generally, as RWC falls from c. 100 to c. 75%, the stomatal conductance (gs) decreases, and with it A. Howeve...

Effects on sugar beet (Beta vulgaris L.) of current and elevated CO2 and temperature alone and in combination and their interactions with abundant and deficient nitrogen supply (HN and LN, respectively) have been studied in three experiments in 1993, 1994 and 1995. Averaged over all experiments, elevated CO2 (600 μmol mol–1 in 1993 and 700 μmol mol...

Diurnal changes in the rate of photosynthesis (A) of mature tea (Camellia sinensis (L.) O. Kuntze) bushes grown at high elevation in the field in Sri Lanka, were related to environmental conditions. Bushes were either unshaded, receiving 100% of incident photosynthetically active radiation (PAR), moderately shaded, (65% PAR) or heavily shaded (30%...

The role of the demand for carbon assimilates (the ‘sink’) in regulating photosynthetic carbon assimilation (Pn: the ‘source’) in response to phosphate (Pi) deficiency was examined in tobacco (Nicotiana tabacum L.). Pi supply was maintained or withdrawn from plants, and in both treatments the source/sink ratio was decreased in some plants by darken...

The nature of the interaction between drought and elevated CO2 partial pressure (pCa) is critically important for the effects of global change on crops. Some crop models assume that the relative responses of transpiration and photosynthesis to soil water deficit are unaltered by elevated pCa, while others predict decreased sensitivity to drought at...

Photosynthesis is an advanced textbook of all aspects concerning the mechanisms of the processes and their interaction with the environment. The fundamental processes are considered and the text provides a comprehensive analysis in a readily accessible format for upper-level and postgraduate students studying plant biology and agricultural sciences...

The use of nitrogen (N) fertilisers in agriculture and horticulture is of major importance for production of sufficient food to maintain the global human population. This book chapter considers the role of N in plant growth culminating in harvested yield, providing an integrated view of the mechanisms upon which food production depends. This review...

*INRA, Unité Ecophysiologie des Plantes Fourragères, Lusignan

To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 micromol m(-2)...

Following an overview of climate change and global crop productivity, the book is divided into 4 sections: the problem-changing biosphere (climatic change and variability, and agricultural contributions to greenhouse gas emissions); crop ecosystem responses to climatic change (rice, maize and sorghum, soyabean, cotton, root and tuberous crops, vege...

Carboxylation and RuBP‐regeneration capacities, which determine light‐saturated photosynthetic rate, were analysed in leaves of spring wheat )Triticum aestivum L. cv. Minaret( grown under different atmospheric CO2 partial pressure )pCa( and N supply regimes. Capacities were estimated from a large number of gas exchange, Rubisco and ATP‐synthase con...

Some photosynthetic processes in tea (Camellia sinensis) were compared with those of sunflower (Helianthus annuus) to identify factors limiting photosynthetic CO2 exchange rate (A) in tea. Two experiments were done under controlled environmental conditions at IACR-Rothamsted, Harpenden, UK. Young tea plants (clone TRI 2025) and sunflower (cv. Print...

Water stress substantially alters plant metabolism, decreasing plant growth and photosynthesis and profoundly affecting ecosystems and agriculture, and thus human societies. There is controversy over the mechanisms by which stress decreases photosynthetic assimilation of CO2. Two principal effects are invoked: restricted diffusion of CO2 into the l...

The effects of micropropagation conditions on avocado (Persea americana Mill.) have been measured in leaves and plants cultured in vitro. The consequences of the type and concentration of sugar in the medium and of carbon dioxide concentration in the atmosphere on the rates of photosynthesis and amounts of ribulose 1,5-biphosphate carboxylase-oxyge...

The global environment is changing with increasing temperature and atmospheric carbon dioxide concentration, [CO2]. Because these two factors are concomitant, and the global [CO2] rise will affect all biomes across the full global range of temperatures, it is essential to review the theory and observations on effects of temperature and [CO2] intera...

To study the direct effects of photosynthesis on allocation of biomass by altering photosynthesis without altering leaf N or nitrate content, phosphoribulokinase (PRK) activity was decreased in trans- genic tobacco (Nicotiana tabacum L.) with an inverted tobacco PRK cDNA and plants were grown at different N levels (0.4 and 5 mM NH4NO3). The activat...

Marama bean, Tylosema esculentum, is a tuberous legume native to the Kalahari region of Southern Africa where it grows under high temperatures (typical daily max 37 degrees C during growing season) and radiation (frequently in excess of 2000 micromol m(-2) s(-1)) in sandy soils with low rainfall. These conditions might be expected to select for inc...

Wheat (Triticum aestivum L.) was grown under CO2 partial pres- sures of 36 and 70 Pa with two N-application regimes. Responses of photosynthesis to varying CO2 partial pressure were fitted to esti- mate the maximal carboxylation rate and the nonphotorespiratory respiration rate in flag and preceding leaves. The maximal carbox- ylation rate was prop...

Responses of durum wheat (Triticum durum, cultivar Karim) to application of nitrogen fertilizer and irrigation have been analysed in the semi-arid areas of Tunisia. The aim is to establish the value, for crop production, of applying N fertilizer under non-irrigated conditions and analyse the mechanisms of responses in two soil types: a clay soil at...

Responses of durum wheat (Triticum durum, cultivar Karim) to application of nitrogen fertilizer and irrigation have been analysed in the semi-arid areas of Tunisia. The aim is to establish the value, for crop production, of applying N fertilizer under non-irrigated conditions and analyse the mechanisms of responses in two soil types: a clay soil at...

Numbers of people and their fossil fuel consumption are increasing, also land use is changing, contributing to increasing atmospheric carbon dioxide (CO2) concentrations and probably increasing global temperatures: by 2100 these may reach 700μmol/mol and 4°C respectively. The consequences for growth and production of the main foods - the cereals wh...

Water stress greatly affects plant processes, including photosynthesis, decreasing dry matter production over much of the earth’s surface so that harvested crop yields are below the genetic potential. Need to provide food and fibre for a large and rapidly growing human population (particularly in drought prone areas) makes the long-sought goal of s...

Tobacco plants (Nicotiana tabacum L.) transformed with an inverted cDNA encoding ribulose 5-phosphate kinase (phosphoribulokinase,PRK; EC 2.7.1.19) were employed to study the in vivo relationship between photosynthetic electron transport and the partitioning of electron transport products to major carbon metabolism sinks under conditions of elevate...

Winter wheat (Triticum aestivuin cv. Mercia) was grown in a controlled-environment facility under simulated Held conditions at ambient (360μmol mol−1) and elevated (690 μmol mol−1) CO2 concentrations. Some of the plants were shaded to mimic cloudy conditions during three periods of about 20d duration between terminal spikelet and start of grain-fil...

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The response of sugar beet to elevated CO2 and wanner temperature has been studied in combination with two nitrogen applications (HN= abundant; LN= deficient). Elevated CO2 increased total-and root dry mass, but had no effect on sucrose percentage in both N treatments. Amino-N and glycine betaine concentration were decreased in HN plants but not af...

Wheat (Triticum aestivum L. cv. Mercia) seedlings grown in full darkness were used for separate measurements of shoot and root dark respiration (R(D)) under 0 μl(CO2) l-1 (R(D)0) and 660 μl(CO2) l-1 (R(D)660). R(D)660 was inhibited, on average, by 24% (R(D)660 = 0.74 * R(D)0, r2 = 0.914) although the measured samples differed in both the proportion...

Sugar beet (Beta vulgaris L., cultivar Celt) plants were grown under simulated field conditions in pots and supplied with adequate or deficient nitrogen (HN and LN, respectively) combined with two CO2 concentrations, ambient (c. 350μmol mol−1 C02—AC), or elevated CO2 (c. 600 μmol mol−1 CO2—HC). Chloroplast structure in mesophyll palisade cells of m...

Spring wheat (Triticum aestivum L.) was grown under optimal nutrition for six weeks at 700 and 350 molmol–1 CO2 and simultaneous measurements of photosystem-II (PSII) chlorophyll fluorescence and gas exchange were conducted on intact attached leaves. Plants grown at elevated CO2 had double the concentration of CO2 at the carboxylation site (Cc) des...

Transgenic tobacco plants containing altered amounts of phosphoribulokinase (PRK) and the chloroplast phosphate translocator (PT) have been produced by transformation with tobacco cDNAs in the sense or antisense orientation expressed from a tobacco rbcS promoter. Plants expressing antisense PRK RNA contained a range of PRK activities from wild type...

Attempts to select C3 plants with slow rates of photo-respiration and increased rates of net photosynthesis have met with little success. This review analyses the properties of mutant genotypes of tobacco (Nicotiana tabacum L. cv. Wisconsin), derived from selection of haploid plants (produced by in vitro mutagenesis of anthers) which survived in CO...

The relation between photosynthetic rate per unit leaf area (Pn), total photosynthesis by canopies and dry matter production (DMP) of crops is reviewed. Although Pn is the driving force for all plant growth, total DMP is determined by processes integrated over the canopy, primarily light interception and thus by leaf area index (LAI) and canopy arc...