Integrated Analysis of Growth and Light Interception in Winter Lettuce II. Differences between Cultivars

‘Integrated growth analysis’ (emphasizing aspectsof crop and plant structure) and ‘light conversion analysis’(stressing the efficiency of interception and photosyntheticconversion of light) have been used to investigate the wintergrowth of different cultivars of butterhead and crisphead typesof glasshouse lettuce. Measurements from ‘Ambassador’ (large-framed butterhead),‘Renate’ (medium-sized butterhead) and ‘Cristallo’(crisphead) were made, statistical progressions were fittedto the primary data and hence estimates of all the analyticalcomponents were derived. Curves for crop growth rate, like those for most other components,followed a generally similar pattern for all three cultivars.In integrated growth analysis, the biomass curve for Ambassadorlay above the curves for the other cultivars. The weight advantagewas initially 60 per cent and it persisted with only a smallreduction (to 40 per cent) until the final harvest. Relativegrowth rate varied little between cultivars because differencesobserved in leaf area ratio were complementary to those seenin net assimilation rate. In light conversion analysis, differences in light interceptingefficiency between cultivars were not statistically significant,though Ambassador attained full interception 4 days earlierthan Renate and 6 days earlier than Cristallo. Differences inlight utilizing efficiency were small and non-significant exceptduring the post-rosette stage when the value for Renate waslower than that of either Ambassador or Cristallo. Deviationsaround the fitted curves were correlated with fluctuations inthe light regime. An assessment is made of the utility and limitations of thetwo procedures. It is concluded that both approaches can assistin analyzing the rate of dry matter production in crops or plantstands. Integrated growth analysis is advantageous when theneed arises to treat individual and population-based attributessimultaneously, while light conversion analysis provides a meansof explicitly incorporating the primary environmental variableinfluencing growth. Lactuca sativa L., lettuce cultivars, growth analysis, crop growth rate, relative growth rate, light interception, light utilization     

Growth of Lettuce, Onion, and Red Beet. 1. Growth Analysis, Light Interception, and Radiation Use Efficiency

A field experiment was carried out to analyse the growth oflettuce, onion and red beet in terms of: (a) canopy architecture,radiation interception and absorption; (b) efficiency of conversionof absorbed radiation into biomass; and (c) dry matter partitioning.Growth analysis, total solar radiation interception, PAR interceptionand absorption by the crop canopy, ground cover, maintenancerespiration of onion bulbs and red beet storage roots were measured.Models for different leaf angle distribution and ground coverwere used to simulate light transmission by the crop canopy. The three crops are shown to have contrasting growth patternsfrom both a morphological and a physiological point of view.Lettuce showed very high light interception and growth afterthe early growth stages but, throughout the growth cycle, thisleafy crop showed the lowest radiation use efficiency due tothe respirational cost of the high leaf area. Onion showed alower early relative growth rate than lettuce and red beet.This was due partly to the low light interception per unit leafarea in the later stages of growth and partly to the low initialradiation use efficiency compared with the other two crops.On the other hand, thanks to more uniform distribution of theradiation inside the canopy, to the earlier termination of leafdevelopment and to the very low level of bulb respiration, onionshowed high radiation use efficiency and was able to producea large amount of dry matter. Red beet leaf posture and canopystructure resulted in high light interception and absorption.Its radiation use efficiency was lower than that of onion, partlyperhaps because of the more adverse distribution of the interceptedradiation fluxes within the canopy and partly because of thehigh respiration cost of a continuous dry-matter allocationto the leaves. However, this crop can accumulate a very largeamount of dry matter as leaf blade development and storage rootgrowth can both continue almost indefinitely, providing continuouslyavailable sinks. Ground cover gave a good estimate of the PAR interception onlyat low values of light interception but, in general, it underestimatedPAR interception in all three crops. Ratios between attenuationcoefficients established by considering PAR or total solar radiationand LAI or ground cover were calculated. Lettuce,Lactuca sativa L. var.crispa ; onion,Allium cepa L.; red beet; Beta vulgaris L. var.conditiva ; growth analysis; light interception and absorption; canopy architecture; ground cover; radiation use efficiency; maintenance respiration rate; dry matter distribution     

Analysis of Light Interception by Single Plants

A formal treatment is proposed for measuring the light fluxintercepted by single plants, either within a stand or as isolatedplants. Methods are suggested for quantifying the light interceptingcapacity of the plant and its light intercepting efficiencyper unit leaf area, and for analysing the control of this efficiencyby between-plant shading within the stand, by within-plant shading,by leaf attitudes and by leaf transmittance. Canopy structure, leaf area, light interception     

Growth Retardants and the Germination of Light Sensitive Lettuce Seed

The effect of the dwarfing compounds chlormequat, B995, and Phosphon D on the germination of lettuce seed in darkness was found to be a depression which could be overcome in part by red light, GA, and kinetin. There was a marked statistical interaction between the growth retardants and all the mitigating treatments except B995 and GA, and light, at 30°C and GA and Phosphon D at 20°C and this implies a biological interaction at the site of action of the growth retardant. It is suggested that the action of the compounds considered is in the establishment of an ordered system since it is unlikely that there would be a common binding site for kinetin and GA.     

LED光源对不同品种生菜生长和品质的影响

以自然光为对照(CK),探讨了LED红光(R)、蓝光(B)和红蓝组合光(RB)对不同品种生菜生长与品质的影响.结果显示:(1)不同光质处理的4个品种生菜的根长、株高及生物量积累等形态及生长指标具有相同的变化规律.(2)植株干鲜重、叶面积及根系活力在R和RB处理下都较大,而在B处理下较小;金祥、高华和永荣的B处理植株可溶性蛋白含量较高;联记、金祥和高华植株的淀粉含量在RB处理下较多,而永荣在R处理下较多;各品种植株可溶性糖含量在R和RB处理下较高,而永荣植株RB处理蔗糖含量较高,其余品种蔗糖含量在R处理下较高;金祥、高华和永荣VC含量在B和RB下较高,联记在RB下较高,各品种在R下均较低;植株总酚含量在各光质处理间无显著差异.(3)联记的硝态氮含量及亚硝酸还原酶对光质敏感,B处理能降低其硝态氮含量及亚硝酸还原酶活性,其他品种的硝态氮含量及亚硝酸还原酶活性在光质处理间无显著差异.研究表明,相同光质下品种间生长无显著差异,而各品种生菜植株在红光和红蓝组合光下生长较好,在红蓝光处理下品质较优,红蓝光是设施栽培生菜的良好光源.     

Growth of Lettuce, Onion and Red Beet. 2. Growth Modelling

Data from a field experiment carried out on growth of lettuce,onion, and red beet were used: (a) to fit logistic, Gompertz,expolinear and ‘Scaife and Jones’ (Journal of AgriculturalScience, Cambridge86 : 83–91, 1976) functions using time,day-degrees and effective day-degrees; and (b) to test a mechanistically-basedmodel that combines the effects of potentially limiting variables,such as temperature and light, and allows for plant zone areain light interception (Aikman and Benjamin,Annals of Botany73 : 185–194, 1994). The use of day-degrees and effective day-degrees instead oftime, in general, improved the fit and gave a better estimateof growth parameters. The best fit was obtained by the Gompertzfunction for lettuce, and by the expolinear function for redbeet and for onion. The expolinear function seemed the mostreliable function in estimating the early relative growth ratewhich is the crucial value in all the mechanistic models. Thezone area model showed very good simulations for lettuce andred beet, but it requires a modification for canopy senescencein onion. Lettuce; Lactuca sativa L. var.crispa ; onion; Allium cepa L.; red beet; Beta vulgaris L. var.conditiva ; growth modelling; logistic; expolinear; Gompertz; zone area; time; day-degrees; effective day-degrees     

Light Interception and Photosynthetic Efficiency in Some Glasshouse Crops

Productivity of glasshouse crops is strongly limited by lightreceipt, and efficient interception and use of light in photosynthesisis correspondingly important. Mature row crop canopies of cucumberand tomato intercepted about 76% of the light incident on theirupper surfaces; about 18% was lost through gaps between therows. Light transmitted through the entire depth of the canopywas reflected back by white plastic on the ground, so that thelower surface of the canopy received approximately 13% of thelight incident on the upper surface. The light flux incidenton the sides of these canopies (c. 2m tall and 6m x 16m in area)amounted to some 20–30% of that incident on the uppersurface. About 32% of daylight falling on the glasshouse (c.9m x 18m in area) was intercepted by the glasshouse structureand glazing; of the 68% entering the house, some fell on headlandsoccupying 35% of the glasshouse area. The loss of light to headlands,and the gain from canopy side-lighting, would be relativelysmaller for larger glasshouses. At near-ambient CO₂ concentrations, net photosynthetic ratesof the cucumber canopy were comparable to those of closed canopiesof other glasshouse and field crops which have maximum lightconversion efficiencies of 5–8µg CO₂ J^–1 at50–200 W m^–2 incident light flux density. Efficiencydecreases only slightly with stronger light. Glasshouse cropswith CO₂ enrichment to 1200 vpm achieve conversion efficienciesof 7–10µg CO₂ J^–1. Efficiencies of utilizationof intercepted light, on an energy basis, reach 6–10%in various field and glasshouse crops with near-ambient CO₂,and reached an exceptional 11% for the cucumber canopy. Glasshousecrops with CO₂ enrichment achieve maximum efficiency of lightenergy utilization between 12% and 13%. Key words: Glasshouse cucumber and tomato, light interception and utilization, photosynthetic efficiency, row crops     

Environmental and Physiological Influences to Isotopic Ratios of N and Protein Status in a Montane Ungulate in Winter

Winter severity can influence large herbivore populations through a reduction in maternal proteins available for reproduction. Nitrogen (N) isotopes in blood fractions can be used to track the use of body proteins in northern and montane ungulates. We studied 113 adult female caribou for 13 years throughout a series of severe winters that reduced population size and offspring mass. After these severe winters, offspring mass increased but the size of the population remained low. We devised a conceptual model for routing of isotopic N in blood in the context of the severe environmental conditions experienced by this population. We measured δ¹⁵N in three blood fractions and predicted the relative mobilization of dietary and body proteins. The δ ¹⁵N of the body protein pool varied by 4‰ and 46% of the variance was associated with year. Annual variation in δ¹⁵N of body protein likely reflected the fall/early winter diet and winter locations, yet 15% of the isotopic variation in amino acid N was due to body proteins. Consistent isotopic differences among blood N pools indicated that animals tolerated fluxes in diet and body stores. Conservation of body protein in caribou is the result of active exchange among diet and body N pools. Adult females were robust to historically severe winter conditions and prioritized body condition and survival over early investment in offspring. For a vagile ungulate residing at low densities in a predator-rich environment, protein restrictions in winter may not be the primary limiting factor for reproduction.     

Light regulation of sink metabolism in tomato fruit : I. Growth and sugar accumulation

Light/dark effects on growth and sugar accumulation in tomato (Lycopersicon esculentum) fruit during early development were studied on intact plants (in vivo) and in tissue culture (in vitro). Through the use of an in vitro culture of tomato fruit, it was possible to investigate the direct effects of light on sink metabolism by eliminating the source tissue. Similar growth patterns were found in vivo and in vitro. Fruit growth in different sugars indicated that sucrose was the best source of carbon for in vitro fruit growth. Fruit growth increased as sucrose concentration increased up to 8%. Darkening the fruit decreased fruit dry weight about 40% in vivo and in vitro. The differences in the CO₂ exchange rate between light and dark grown fruit indicated that light stimulation of fruit growth was due to mechanisms other than photosynthesis. Supporting this conclusion was the fact that light intensities ranging from 40 to 160 micromoles per square meter per second had no significant influence on fruit growth, and light did not increase growth of fruit cultured with glucose or fructose as a carbon source. However, light stimulated fruit growth significantly when sucrose was used as the carbon source. Light-grown fruit took up 30% more sucrose from the same source and accumulated almost twice as much hexose and starch as dark-grown fruit. A possible expansion of an additional sink for carbon by light stimulation of starch synthesis during early development will be discussed.     

Analysis of Growth and Yield of Winter and Spring Wheats

In a field experiment to investigate the physiological causesof variation in yield between autumn- and spring-sown wheatand between old and new varieties, the grain yields of the winterwheats were 3-15 per cent, greater than of the spring ones andthe new varieties Cappelle-Desprez and Jufy I yielded 40-70per cent, more than Squarehead's Master and Atle. Nitrogen fertilizerincreased the yields of Cappelle-Desprez and Jufy I more thanof Atle, and decreased the yield of Squarehead's Master by makingit lodge. Until ear emergence the winter varieties had greater leaf-areaindices (L) and dry weights, but smaller net assimilation rates(E), than the spring varieties. Square-head's Master had greaterL but smaller E, and similar dry weight to Cappelle-Desprez.Jufy I had similar E to Atlc, but greater L and dry weight.Nitrogen increased L and dry weight, but decreased E. All thedifferences in E between varieties and nitrogen treatments couldbe explained by the opposite effects on L, that is to say, thedifferences in E were caused by variation in mutual shadingarising from the differences in L and not by changes in leafphysiology. L of winter wheat reached its maximum at the end of May, butL of spring wheat continued to increase until ear emergence.Afterwards Ldecreased more rapidly for winter than for springwheat, so that eventually spring wheat had the greater L. Thesedifferences in the time changes of L partially compensated forthe shorter growth period of spring wheat, and tended to equalizethe grain yield from winter and spring sowings. After ear emergence total dry weight of winter varieties continuedto be greater than of spring ones, but the difference in dryweight of ears was much smaller because ear: shoot dry-weightratio was greater for the spring varieties. Total dry weight,ear dry weight and ear: shoot ratio were all greater in thenew than in the old varieties. Leaf area duration (D) afterear emergence was slightly greater for the winter than for thespring varieties and similar for old and new. The apparent efficiencyof this leaf area in grain production, measured by the grainleaf ratio (ratio of grain dry weight to D), was similar forwinter and spring varieties but greater for new than for old.This suggests that Cappelle-Desprez and Jufy I have higher grainyields because their ears photosynthesize more than do the earsof Squarehead's Master and Atle. Before ear emergence winter varieties had more shoots than springones, and old varieties more than new. After ear emergence therewere only small differences in numbers of ears; percentage survivalwas greater for spring than for winter and for new than forold varieties. Differences in dry weight between varieties were not causedby differences in nitrogen uptake.     

Water Content and the Responsivity of Lettuce Seeds to Light

Lettuce seed (Lactuca sativa L. cv. Grand Rapids) prevented from attaining maximum water content are still able to respond to irradiation if the seed moisture content is above 6%. When the limitation to water uptake is by immersion in a solution of either polyethylene glycol 400 (PEG 400), mannitol, or sucrose, the responsiveness of the seed is lessened. With PEG 400 the molarity which reduces germination by about 50% is 0.03 while mannitol and sucrose must be present at 0.07M and 0.05 M respectively to bring about the same reduction. While red light overcomes any additional effect 0.1 M mannitol and 0.025 M PEG 400 have on lettuce seed at 30°C (at which temperature the sample was positively photoblastic), irradiation did not overcome the effect of 0.1 M sucrose. Gibberellic acid did not have any effect on any of the treated seed. The solutes used cannot be considered as inert. Some chemical activity is associated with them and it is unwise to consider using these molecules to establish a particular level of water potential in the liquid bathing the seed.     

Correlative Studies on Plant Growth and Metabolism II. Effect of Light and of Gibberellic Acid on the Changes in Protein and Soluble Nitrogen in Lettuce Seedlings

Protein and soluble nitrogen distribution in different parts of lettuce seedling was studied in light and darkness and in presence and absence of gibberellic acid. In dark, applied gibberellic acid failed to show any marked effect on the nitrogen changes in lettuce. Light inhibits translocation of nitrogen reserves from the cotyledons. Gibberellic acid reverses the light inhibition of longitudinal growth but has no effect on the inhibition of translocation from the cotyledons. Light grown, gibberellic acid treated seedlings exhibit a pattern of protein and soluble-N which is characteristic of the dark grown seedlings. Thus gibberellic acid not only causes morphological reversal of light inhibition but also shifts the nitrogen metabolism of light grown plants, close to that of plants grown in darkness.     

Effects of Aflatoxin on Germination and Growth of Lettuce

The relative susceptibility of 30 cultivars of lettuce to inhibition by aflatoxin was studied. Seed germination was not inhibited by concentrations as high as 1,000 mug/ml in cultivar Imperial 44 or by 100 mug/ml in the remaining cultivars. Hypocotyl elongation was inhibited by 46 to 68% at a concentration of 100 mug of aflatoxin per ml. Seedlings exposed to aflatoxin did not become chlorotic. The similarity between the morphological reaction of plants to coumarin and aflatoxin suggests a common mode of action, but further studies of the physiological basis for the inhibitory reactions induced by these compounds will be necessary before such conclusions will be valid.     

光温互作和培养基中的附加成分对香蕉试管苗生长的影响

光照强度和温度对香蕉试管苗的长根数、总根数、苗高和青叶数影响极显著。光照强度为10μmol·m-2·s-1时,总根数和长根数最多;光照强度为25μmol·m-2·s-1时,青叶数最多,苗高随其升高而降低。温度为28℃时,总根数和长根数最多;26℃时,苗最高;32℃时,青叶数最多。培养基中添加85mg·L-1磷酸二氢钾后,试管苗的鲜重、干重、苗高、茎径、叶长、叶宽和青叶数增加;添加5mg·L-1腺嘌呤后,鲜重、茎径和叶长增加;添加4.8mg·L-1多效唑的发根数、最长根长、叶鲜重和茎径显著增加,苗高降低。     

Compensation Points and Carbon Dioxide Enrichment for Lettuce Grown Under Glass in Winter

Measurements of , the minimum intercellular-space carbon dioxideconcentration or carbon dioxide compensation point, made attwo temperatures and at light intensities from 15 to 1,500 f.c.,were used to study the relation between the compensation pointsfor light and carbon dioxide. This was found to be hyperbolicand consistent with the Warburg–Maskell model for photosynthesis.The apparently beneficial effects of carbon dioxide enrichmentof the atmosphere at increased temperature, found in practicewith lettuce or other crops grown under glass at light intensitiesthat might be expected to be severely limiting, must be in partdue to the reduction of the light compensation point at highcarbon dioxide concentration.     

Environmental and Parental Influences on Offspring Health and Growth in Great Tits (Parus major)

Sexual selection requires both that there is heritable variation in traits related to fitness, and that either some of this variation is linked to traits of the parents, and/or that there are direct benefits of choosing particular individuals as mates. This suggests that if direct benefits are important offspring performance should be predicted by traits of the rearing adults. But if indirect benefits are more significant offspring performance should be predicted by traits of the adults at the nest-of-origin. We conducted cross-fostering experiments in great tits (Parus major) over four years, in two of which we manipulated environmental conditions by providing supplemental food. In a third year, some nestlings were directly supplemented with carotenoids. Nestlings in broods whose rearing adults received supplemental food were heavier and had improved immune responses even when controlling for body mass. Nestling immune function was related to measures of the yellow plumage color of both the rearing male and the putative father. Nestling body mass was influenced by the coloration of both the rearing female and the genetic mother. Our results suggest that features of both their social and putative genetic parents influence nestling health and growth. From this it would appear that females could be gaining both direct and indirect benefits through mate choice of male plumage traits and that it would be possible for males to similarly gain through mate choice of female traits.     

The Effect of Temperature and Light on the Germination of Lettuce Seeds

‘Grand Rapids’ lettuce. seed will not germinate in darkness at 30°. An exposure in temperatures between 5°C and 25°C for a short period after the initiation of germination can effectively overcome the high temperature imposed dormancy. If the exposure to low temperature is from the beginning of germination it is less effective. The low temperature induced germination is not reversed by far red light of 725 nm and seed not responding to the low temperature do respond in a classical fashion to red and far red irradiations. It is considered that the results justify acceptance of the hypothesis that an inhibitor of germination is produced during the initial stages of germination and that this formation is strongly temperature dependent so that there is much accumulation. At low temperatures an alternative metabolic pathway predominates leading to the production of an essential metabolite. At high temperatures this metabolite is produced from the inhibitor (or inert compound) by a mechanism under the control of the phytochrome system.