Stability of the Nitrogen Concentration of Inoculated White Lupins during Pod Development

The general pattern of decrease of the 'critical' plant N concentration(i.e. minimum concentration required for maximum growth rate)during growth has been described for several C₃ non grain-legumespecies, and this can be used as a reference curve for diagnosisof N nutrition in these species. The present study was undertakento investigate changes of N concentration during growth of agrain legume, in different conditions of N nutrition. Whitelupin (Lupinus albus L.) was grown for six crop seasons in fieldtrials in which inoculation with Rhizobium lupini, nitrogenfertilizer rate, cultivar and plant density were density weremanipulated. The yield and dry matter production of noninoculatedplants were lower than, or at the best similar to, those ofinoculated plants, whatever the level of N supply. From anthesisto the beginning of seed filling, the N concentration of shootsof inoculated plants was found to be remarkably stable betweenyears, N fertilization regimes, cultivars, and for individualplants within a plot. Nitrogen concentration only varied withplant density. By contrast, the N concentration of noninoculatedplants was highly variable and generally lower than that ofinoculated plants, whatever the level of N supply. The highand stable N concentration of inoculated plants did not appearto be necessary for maximum growth rate but seemed to be requiredfor maximum production of seed dry matter and N. The potentialuse of these results to diagnose, in any white lupin crop, aninefficiency of the lupin-R. lupini interaction is evaluated.Copyright1993, 1999 Academic Press Lupinus albus L., white lupin, N₂ concentration, inoculated plants, non-inoculated plants, N₂ fixation efficiency, diagnosis     

Density Effect on the Fruit-set, Seed Crop Viability and Seedling Vigour of Abies pinsapo

Variation in fruit-set, cone crop, seed viability and seedlingvigour ofAbies pinsapoBoiss. were recorded at two differentstand densities during four consecutive years (1990–1993).In this period only two cone crops were observed (1991 and 1992).Extreme differences were found in response to density. In thelow density stand trees had a greater seed-cone production andfruit-set in each of the two crop years. Also, significant differenceswere recorded in the seed crop viability: in the low densityzone average seed viability was only 21% whereas in the highdensity one it was 82%. Other important differences such ascone size, number of seeds per cone and seedling vigour wererecorded at different densities. The results suggest that bothpollen availability and pollen origin in low density standsinfluence the frequency and quality of filled seeds. The resultshave practical implications for the management ofA. pinsapoforseed production and subsequent reforestation. Abies pinsapo; inbreeding; mating system; plant density; cone crop; seed viability; seedling vigour; Mediterranean fir     

The Influence of Genes ar and n on Senescence in Pisum sativum L.

The effect of genes ar (violet flowers, small hilum) and n (thick,fleshy pod wall) on whole plant in senescence peas was examinedby comparing Ar- with arar and N- with nn plants in segregatingprogenies. Homozygosity for ar or n significantly delayed the time whenthe plants were ready for harvest of their entire seed crop.These genes did not delay either the onset of reproduction orthe onset of apical arrest in the first instance. However, whereasAr- N- plants almost invariably senesced and died as the firstseed crop matured, the majority of arar and/or nn plants entereda period of secondary growth and a further fruiting cycle. Comparedwith Ar- plants, arar plants had over twice as many pods andseeds but individual seeds were 58 per cent lighter and totalseed yield (wt) was 19 per cent less. Pod length was unaffected.Compared with N-plants, nn plants had shorter pods (16 per cent),fewer seeds per pod (21 per cent), smaller seeds (20 per cent)and a lower total seed yield (wt 14 per cent less). It appearsthat ar and n impose a lower metabolic drain per reproductivenode as a consequence of their effects on hilum anatomy andpod morphology, respectively. These mutants disrupt the normalpattern of monocarpic senescence by breaking the coordinationbetween apical arrest and subsequent events. The developingseed crop delimited by the first arrest fails to cause plantdeath, possibly because sink size is less than in normal counterparts. Pisum sativum L, garden pea, senescence, hilum, pod, seed size, genetics     

Effects of Intercropping on Growth and Reproductive Capacity of Late-emerging Senecio vulgaris L., with Special Reference to Competition for Light

Due to increased emphasis on long-term management of weed populationsin cropping systems with a reduced reliance on herbicides, theproduction of seeds by weeds that emerge after the criticalperiod for weed control is increasingly important. It was hypothesizedthat increased soil cover and light interception by a crop canopywould shorten the critical period for weed control and reducegrowth and fecundity of late-emerging weeds. This hypothesiswas tested in a series of field and glasshouse experiments inwhich competition for light was manipulated. Senecio vulgaris,an important weed in vegetable production systems, was chosenas the target plant, and canopies of pure and mixed stands ofleek and celery were used to provide shade. The time courseof light interception differed among the crop canopies. Increasingcompetition for light caused morphological changes to S. vulgaris,including a vertical shift in leaf area distribution. Increasedshading reduced biomass, capitula:shoot ratio and seed productionof S. vulgaris. However, the viability of seeds produced bythe shaded weed plants was not affected. Results indicate thatintercropping can increase light interception in a weakly competitivecrop such as leek and can contribute to weed suppression ina long-term strategy for weed management. Copyright 2001 Annalsof Botany Company Competition for light, late-emerging weeds, critical period, Apium graveolens L., celery, Allium porrum L., leek, Senecio vulgaris L., common groundsel, seed production, weed management, intercropping     

Validation of the Principal Axis Model (PAM) and its Application to Genotype Selection in Field Pea (Pisum sativum L.) Crops

The principal axis model (PAM) uses a principal axis and anellipse to characterize the variation in the relationship betweenthe seed (SWT) and plant (PWT) weights of individual plantswithin a crop. The theoretical linkage between the magnitudeand variability of plant harvest index (PHI), and thereforeseed yield per unit area, and changes in the components of thePAM was examined using data from four field pea (Pisum sativumL.) genotypes sown at 9, 49, 100, 225 and 400 plants m^-2. Astrong linear relationship (R ²>93.8%) between SWT and PWTand a negative SWT-axis intercept were confirmed for all crops.Analyses indicated that decreased variability of PHI withina crop would result from selection to: (a ) increase the SWT-axisintercept of the PAM; (b ) increase the slope of the PAM; (c) optimize the ellipse location; and (d ) minimize the deviationaround the principal axis. The first three methods were usedto explain yield differences (P <0.05) among genotypes ofdifferent populations. A potential strategy for single plant selection based on thePAM is proposed. This may enable early generation (F₄) selectionof small, high performing plants that may be ideal crop ideotypes.A theoretical example of the strategy is presented, with differencesamong selections based on the PAM, SWT or harvest index highlighted. Field pea(Pisum sativum L.); genetic harvest index; minimum plant weight; plant harvest index; principal axis model; plant population; seed weight; selection criteria     

A Population Study to Aid the Selection of Improved Dried Pea (Pisum sativum) Crop Plants

The effect of genotype and plant density, over the range from100 to 277 plants m^–2, on plant to plant variation inprecision sown microplots has been assessed for three ‘leafless’(afafstst) pea (Pisum sativum) lines. This range of plantingdensities did not significantly affect the total above groundbiological yield per unit area of two of the genotypes (BS5and BS4) whereas the biological yield of the third (BS151) declinedat densities above 156 plants m^–2. The differences weredue to changes in seed yield. The effect of planting densityon the variation between plants for biological yield withinthe microplots differed between the genotypes. The distributionpattern of BS4 and BS5 changed from normal to skewed with increaseddensity, while the distribution for BS151 remained skewed atall planting densities. The differences between the three genotypes in the proportionof biological yield partitioned into seed yield (harvest index)on a unit area basis was due almost entirely to the differencesin structure of the plant populations. The maximum level ofpartitioning by individual plants was similar for all threelines. The difference between this maximum for an individualand the crop harvest index therefore represents the area forimprovement of crop harvest index through breeding. It is suggestedthat improvements in dried pea yields will come, therefore,by selecting plants which form more uniform populations withregard to plant size and to the proportion of plant biomasspartitioned into seed (plant harvest index). Pisum sativum, leafless pea, population, genetic variation, distribution patterns, harvest index     

TEMPORAL VARIATION OF FLOWER AND FRUIT SIZE IN RELATION TO SEED YIELD IN CELANDINE POPPY (CHELIDONIUM MAJUS; PAPAVERACEAE)

Ecological and evolutionary studies typically consider variation in single reproductive characters in isolation, without considering how they might be correlated with other reproductive and vegetative characters. In our study, we examined temporal patterns of variation and correlation in flower diameter and fruit length during a reproductive phase in two Massachusetts populations of the herb, Chelidonium majus. We also examined the relationships of such variation to measurements of seed yield components (mean seed weight and number per fruit) and aspects of plant vegetative size. Most of the variation in the sizes of reproductive characters occurred within individual plants, instead of among plants or between populations. Flower and fruit sizes as well as seed number per fruit declined significantly during the season in both populations. Only mean seed size per fruit was relatively stable for individual plants in both populations. Conserving resources by a gradual reduction in the size of reproductive characters over the season may be a strategy for maternal plants to continue seed production. The strong, persistent patterns of correlation between certain characters, such as flower and fruit size, in spite of extensive phenotypic plasticity, was interpreted as indirect evidence for developmental correlation. Furthermore, vegetatively larger plants produced not only more flowers and fruits, but also consistently larger flowers and fruits. The results emphasize that variation in fitness characters, such as seed size and number, should not be viewed in isolation from vegetative characters, flower, and fruit sizes in ecological and evolutionary studies, if the goal is to understand the mechanisms of natural selection in wild populations.     

Effect of Molybdenum and Inorganic Nitrogen on Molybdenum Redistribution in Black Gram (Vigna mungo L. Hepper) with Particular Reference to Seed Fill

Seeds used to plant a crop may contain sufficient molybdenum(Mo) to prevent subsequent Mo deficiency in the crop even whenthey are sown on Mo deficient soils. However, little is knownabout either the sources of the Mo acquired by the seed, orthe timing of its redistribution during seed development. Aglasshouse experiment was set up to examine the effect of Mosupply and nitrogen source on the redistribution of Mo withinblack gram, from full flowering to seed maturity. Treatmentscomprised two sources of N (symbiotic N₂fixation, NH₄NO₃), twolevels of Mo supply [nil (-Mo), 0.64 mg Mo kg^-1soil (+Mo)] andfour harvests (full flowering, early pod setting, late pod fillingand seed maturity). The redistribution of Mo in black gram wasexamined by determining changes over time in the content ofMo in plant parts at each growth stage. Molybdenum supply and the plant growth stage strongly affectedthe redistribution of Mo to the seed. In -Mo plants relianton symbiotic N₂fixation, Mo redistributed from roots, stemsand leaves was the only source of Mo for reproductive developmentsince, from full flowering until maturity, there was no netincrease in whole plant Mo. For pod and early seed development,the roots were the major source of Mo in -Mo plants. After latepod filling, nodules replaced roots as the major source of Mofor seed fill in -Mo plants. By contrast, for +Mo plants relianton symbiotic N₂fixation, Mo taken up from the soil after fullflowering could have supplied nearly 50% of the seed Mo. Themajor sources of Mo for seed filling in +Mo plants were middlestem leaves during early podding, and middle stems and pod wallsfrom late podding. Supplying NH₄NO₃to plants from sowing had little effect on Modistribution or redistribution in +Mo black gram plants. However,in -Mo plants it accelerated the loss of Mo from middle stemsand their leaves compared to nodulated plants. Black gram; Vigna mungo L. Hepper; distribution; molybdenum; nitrogen; nodules; redistribution; seed fill     

Retrospect and prospects of plant metabolic engineering

With the advancement of biotechnological tools and techniques such as next generation sequencing, RNAomics, epigenomics, gene silencing, plant, microbe transformation, proteomics and metabolomics, the understanding of metabolic pathways and their manipulation for the desired characters became feasible. Metabolic engineering has been successful in the production of golden rice, bioprocess for artemisinin production, flavonoids in plant and microbes as well as generated biotic and abiotic stress tolerance in several crop plants. In view of the significance of metabolic engineering, this article includes recent techniques developed and their use in manipulation of glyoxalase metabolism for multiple abiotic stress tolerance in plants. The importance of engineering of flavonoids pathway for high value antioxidants production as well as improving the biotic and abiotic stress tolerance has been documented. Importance and success of metabolic engineering has been realized by its promising hope for sustainable technologies of bioactives production for mankind’s health as well as in the generation of improved crop varieties.

     

Theoretical Analysis of Yield of Field Pea (Pisum sativum L.) Crops using Frequency Distributions for Individual Plant Performance

Variability among individual plants causes low seed yields infield pea (Pisum sativum L.) crops. To quantify this variability,an empirical principal axis model (PAM) was developed whichhas two components: (a ) a principal axis, representing therelationship between the seed weight (SWT) produced and plantweight (PWT) of individual plants; and (b ) an ellipse, whichcharacterizes the scatter of individual values around the axis.To develop the model, plant-to-plant variability was simulatedby systematically changing the mean and standard deviation (s.d.)of frequency distributions for SWT and PWT. Changes in the interceptand slope of the principal axis and the location and shape ofthe associated ellipse were used to describe the plant-to-plantvariability. Differences in the mean SWT or PWT altered the location of theellipse. When changes in the s.d. values were equal for SWTand PWT, the dimensions of the ellipse changed, but the axesratio was constant. Non-proportionate changes in the s.d. valuescaused rotation of the principal axis and altered the shapeof the ellipse. The effect of differences in the PAM on plant harvest index(PHI) was also examined. When the intercept of the principalaxis passed through the origin, PHI was independent of PWT,and equal to the gradient of the axis. However, when the SWT-axisintercept was negative, indicating that a minimum plant weightwas required for seed production, the relationship between PHIand PWT was asymptotic. This relationship is of major importancefor interpreting differences in PHI distributions, and thuscrop harvest index and seed yield among crops. Field peas (Pisum sativum L.) individual plants; plant harvest index; plant weight; principal axis model; seed weight; simulation     

Growth and Nitrogen Status of Soilless Tomato Plants Following Nitrate Withdrawal from the Nutrient Solution

The effects of withdrawing nitrogen (N) from the nutrient solutionof adult tomato plants growing in rockwool in a greenhouse wereinvestigated over a 6 week period during fruit production. Thetreatment reduced total plant growth after a lag period of about2 weeks. The commercial fruit yield after 6 weeks of N deprivationwas 7.7 kg m^-2compared to 9.3 kg m^-2in control plants. Duringthe experiment, growth of the -N plants was fuelled by N reservescontained in both the substrate (rockwool) and in plant organs.The nitrogen budget calculated for -N plants showed that onlya small amount of organic-N was readily available for internalcycling from organs such as stems. It served mainly to feedgrowing fruits which were the main sinks in the plant. The studyalso established that stores of nitrate-N were fully depletedbut it took 45 d for the -N plants to metabolize completelytheir nitrate reserves. This indicates that internal nitrateis not a readily-accessible store of labile N. An estimationof the critical N concentration (%N_c) in the aerial dry matterwas made from the data. Thus, for a crop yielding about 9.9tons DM ha^-1, %N_cwas close to 2.5%. This result is discussedin light of existing models that describe the ontogenic declinein %N_cin dry biomass of C₃plants. The study indicates that thecurrent regime of N fertilization practised in soilless culturesnot only leads to ineffective nitrogen use but also to largelosses of N to the environment; N concentrations should be decreasedin feeding recipes. The use of N-free nutrient solutions priorto the termination of plant culture may also be a means of limitingthe loss of eutrophying elements, such as nitrate, to the environment.Copyright 2001 Annals of Botany Company Lycopersicon esculentum, tomato, organ dry biomass, critical nitrogen concentration, compartment, rockwool, nitrate interruption, distribution, reserves     

Effect of Removal of Flower Buds, Open Flowers, Young Pods and Shoot Apex on Growth and Pod Set in Soybean

The complete removal of the reproductive structures once andshoot apices of soybeans (Glycine max L. Merrill) during earlyanthesis but before the rapid seed development stage significantlyincreased flowering and pod set in greenhouse and field grownplants. The treated plants had darker green leaves, shorterstems and petioles and retained their chlorophyll content longerthan control plants. Pod maturation was also delayed. Althoughdecapitation and the removal of reproductive structures increasedthe number of 3- or more-seeded pods in all varieties tested,seed weight per plant was not consistently increased. The possibleinvolvement of endogenous hormones in pod set and multi-loculepod production in soybeans is discussed. Key words: Glycine max (L.) Merr, Reproductive structures, Shoot apex, Growth, Flowering, Pod set, Multi-locule pods     

Population ecology of wild sunflowers: effects of seed density and post-dispersal vertebrate seed predators

Assessing the effects of seed density on the population dynamics of wild plant species with crop relatives will be vital in determining the potential effects of introducing traits into wild populations as a result of crop-to-wild gene flow. We examined experimental sunflower (Helianthus annuus) patches in eastern Kansas to determine the effects of seed density and predation on seedling recruitment and seed production in the next generation. High seed density treatment plots had significantly more seedlings and adult plants than did low seed density treatment plots. Overwinter vertebrate seed predator exclusion treatments resulted in increases in plant density compared to plots in which vertebrates were not excluded. Control patches (no seeds added) contained virtually no plants. Head production and estimated total seed production for a patch were not statistically different among treatments (excluding control plots). Although initial seed density and vertebrate post-dispersal seed predation do appear to have effects on seedling recruitment, neither appear to be limiting seed production of competing adult plants. Therefore, variation in seed densities (over the range examined) may have limited effects on local population dynamics. It is important to note that the choice of seed densities may affect the results obtained: the seed densities used in this study may, in retrospect, be higher than in the small roadside populations typical in eastern Kansas, yet other natural sites have much larger densities. Further, the effects of increased seed density at a local site may have other important effects such as altering metapopulation dynamics through increased long-distance dispersal or increased local seed bank size.     

Direct and indirect effects of pollinators and seed predators to selection on plant and floral traits

Although flowering traits are often assumed to be under strong selection by pollinators, significant variation in such traits remains the norm for most plant species. Thus, it is likely that the interactions among plants, mutualists, and other selective agents, such as antagonists, ultimately shape the evolution of floral and flowering traits. We examined the importance of pollination vs pre-dispersal seed predation to selection on plant and floral characters via female plant-reproductive success in Castilleja linariaefolia (Scrophulariaceae). C. linariaefolia is pollinated by hummingbirds and experiences high levels of pre-dispersal seed predation by plume moth and fly larvae in the Rocky Mountains of Colorado, USA, where this work was conducted. We first examined whether female reproduction in C. linariaefolia was limited by pollination. Supplemental pollination only marginally increased components of female reproduction, likely because seed predation masked, in part, the beneficial effects of pollen addition. In unmanipulated populations, we measured calyx length, flower production, and plant height and used path analysis combined with structural equation modeling to quantify their importance to relative seed set through pathways involving pollination vs seed predation. We found that the strength of selection on calyx length, flower production, and plant height was greater for seed predation pathways than for pollination pathways, and one character, calyx length, experienced opposing selection via pollination vs seed predation. These results suggest that the remarkable intraspecific variation in plant and floral characters exhibited by some flowering plants is likely the result of selection driven, at least in part, by pollinators in concert with antagonists, such as pre-dispersal seed predators. This work highlights the subtle but complex interactions that shape floral and vegetative design in natural ecosystems.     

植物谷氨酰胺合成酶研究进展及其应用前景

氮素是制约作物产量的主要营养元素之一,谷氨酰胺合成酶(Glutamine synthase,GS;EC 6.3.1.2)是氮素代谢途径中的关键酶。目前,拟南芥、水稻、小麦和玉米等植物中的GS成员均已被分离鉴定。研究表明,超表达GS能够提高植物对氮素的利用效率,从而在植株的生长发育特别是产量形成过程中发挥重要作用,但是其功能在不同植物上并不完全一致,可能与GS基因受到转录和翻译后等水平的调控有关。以下综述了植物GS基因分类、QTL定位、对氮素代谢响应、组织表达特异性、生物学功能及其分子调控机制等方面的研究进展,并展望了植物GS基因的应用前景,以期为利用GS基因来提高植物氮素利用效率提供具有参考价值的信息。     

Seed Production in Leafless and Conventional Phenotypes of Pisum sativum L. in Relation to Water Availability Within a Controlled Environment

Water requirements in relation to seed production was studiedin near-isogenic lines of leafless (afafstst) and conventional(++++) pea plants (Pisum sativum). The plants were grown toseed maturity in pots in a controlled environment under conditionsof high, medium and low irrigation levels. When each genotypewas irrigated independently and on demand and the soil moisturecontent maintained at 65–80 per cent of full capacitythere was no significant phenotypic difference in water useefficiency (WUE), defined as g d. wt seed per kg H₂O utilized.There existed genotypically-controlled upper and lower limitsto yield between which the total dry weight of seed per plantcan be determined by water availability. There was no significantdifferential effect of genotype or of irrigation treatment onthe number of pods, number of seed, unit seed dry weight andbiological yield per plant. There was significant interactionon stem length, and leaf area at specified nodes. When the wateractually required in relation to the water available was takeninto account, the leafless phenotype consistently utilized 33–38per cent less water and produced a correspondingly lower totaldry weight of seed than the conventional counterpart. Independentlyof regime the total dry weight seed per phenotype remained anear constant proportion of the above-ground biomass. Pisum sativum L., garden pea, leafless peas, seed production, water availability     

Seed quality effects in bulb onions (Allium cepa L.)

The nature and persistence of seed quality effects produced by a range of seed production treatments was investigated in the autumn-sown onion crop. Genotypically equivalent seed lots raised in different glasshouses within the same year were found to germinate at significantly different rates. The seed lot which emerged earlier produced larger seedlings and this difference in size persisted throughout the growing period. In a comparison between the effects of hand crossing and self-pollination techniques the hand crossing method produced a much lower total seed yield but heavier seeds and larger plants. The induced effects persisted throughout the year but were not significant in the mature bulb characters. The implications of these results upon the control of seed production for plant breeding and genetical experiments is discussed.     

Coping mechanisms for crop plants in drought-prone environments

Background: Drought is a major limitation to plant productivity. Variousoptions are available for increasing water availability andsustaining growth of crop plants in drought-prone environments. Scope: After a general introduction to the problems of water availability,this review focuses on a critical evaluation of recent progressin unravelling mechanisms for modifying plant growth responsesto drought. Conclusions: Investigations of key regulatory mechanisms integrating plantgrowth responses to water deficits at the whole-organism, cellularand genomic levels continue to provide novel and exiting researchfindings. For example, recent reports contradict the widespreadconception that root-derived abscisic acid is necessarily involvedin signalling for stomatal and shoot-growth responses to soilwater deficits. The findings bring into question the theoreticalbasis for alternate-side root-irrigation techniques. Similarly,recent reports indicate that increased ABA production or increasedaquaporin expression did not lead to improved drought resistance.Other reports have concerned key genes and proteins involvedin regulation of flowering (FT), vegetative growth (DELLA),leaf senescence (IPT) and desiccation tolerance (LEA). Introgressionof such genes, with suitable promoters, can greatly impact onwhole-plant responses to drought. Further developments couldfacilitate the introduction by breeders of new crop varietieswith growth physiologies tailored to improved field performanceunder drought. Parallel efforts to encourage the introductionof supplementary irrigation with water made available by improvedconservation measures and by sea- or brackish-water desalination,will probably provide comprehensive solutions to coping withdrought-prone environments.     

Transformation and Characterization of Transgenic Plants of Solanum dulcamara L.--Incidence of Transgene Silencing

A transformation system is described for Solanum dulcamara usingthe supervirulentAgrobacterium tumefaciens strain 1065, carryingboth the ß-glucuronidase (gus) and neomycin phosphotransferaseII (npt II) genes adjacent to the right and left T-DNA borders,respectively. Leaf explants were more efficient for the productionof transformed plants compared to stem explants on medium containing50 mg l^-1of kanamycin sulphate. A 1:10 (v:v) dilution of anovernight culture ofAgrobacterium gave optimal transformationin terms of transgenic plant regeneration. From a total of 174kanamycin-resistant plants selected by their antibiotic resistance,16 failed to exhibit GUS activity. Southern analysis revealedthat these GUS-negative transformants originated from threeindependently transformed cell lines. Restriction enzyme analysesshowed that the GUS-negative plants had both the gus and nptII genes integrated into their genome (one plant had a singlecopy of each gene; the other two plants had multiple copies),with major rearrangement of the gus gene occurring in plantswith several copies of the transgene. GUS-negative plants showedleaf malformations, delayed flowering and a reduction in flower,fruit and seed production compared to GUS-positive and non-transformed(control) plants. Although gene silencing of the gus gene occurred,albeit at a low frequency (9.2%), the transformation systemdescribed generates large numbers of phenotypically normal,stably transformed plants. Copyright 2000 Annals of Botany Company Agrobacterium -mediated transformation, gene silencing, Solanum dulcamara L. (Bittersweet, Woody Nightshade), T-DNA truncation, transgene expression     

Shoot Dry Weight, Chlorophyll and UV-B-absorbing Compounds as Indicators of a Plant's Sensitivity to UV-B Radiation

When studying the effects of ultraviolet-B (UV-B) radiationon plants, a good measure of UV-B sensitivity is a decreasein dry weight, since this reflects the cumulative effect ofmany small disruptions in plant function. Measurements of chlorophyllconcentration and the level of UV-absorbing compounds are alsoused to gauge plant health during and after UV-B exposure. Whena variety of vegetable crop plants were screened for UV-tolerance,it was found that the levels of chlorophyll and UV-absorbingcompounds did not correlate with sensitivity. Biomass accumulationwas, however, correlated with UV-sensitivity; plants that accumulatedmore biomass over a 2-week period were more likely to be UV-Bsensitive. This suggests that a rapid growth rate renders plantsmore sensitive to the injurious effects of UV-B radiation. Copyright2000 Annals of Botany Company UV-B radiation, UV-absorbing compounds, chlorophyll, biomass production, UV-B sensitivity, Capsicum frutescens,Cucurbita pepo , Chicorium endivia, Lactuca sativa, Phaseolus vulgaris, Solanum melongena, Spinacia oleracea, Sinapis alba