Influence of Tops and Roots on Net Assimilation Rate of Sugar-beet and Spinach Beet and Grafts between them

Sugar-beet has a larger storage root and greater net assimilationrate (E) than spinach beet. To determine whether the greaterroot was a result or cause of the greater E, grafts were madebetween tops and roots of sugar-beet and spinach-beet in allfour possible combinations. Grafted plants with sugar-beet roots had greater E and rootdry weight, less leaf area and top dry weight and lower concentrationof sugar in the leaf lamina, than those with spinach-beet roots,irrespective of the type of top. Grafted plants with sugar-beettops had greater E, total and root dry weight, but less leafarea, than those with spinach-beet tops, irrespective of thetype of root. The difference in E between grafted plants withsugar-beet tops and spinach-beet tops was similar to that betweengrafted plants with sugar-beet roots and spinach-beet roots.It increased with time to 60 per cent. Increases in E probably represent increases in rate of photosynthesis.Sugar-beet roots probably increased photosynthesis by providinga better sink for assimilates than spinach-beet roots.     

Competition for Nitrogen and Potassium in Agropyron repens

Stands of Agropyron repens (couch grass) and single young sugar-beetplants were grown in pots, separately and in competition, withnitrogen and potassium each supplied at three rates in a factorialdesign. Both nitrogen and potassium increased relative growth-ratesof sugar-beet leaves and crowns and fresh-weight/dry-weightratios of all plant parts; the responses were usually curved,the high nutrient levels having little more effect than theintermediate levels. Competition decreased relative growth-ratesand freshweight/dry-weight ratios of all plant parts and alsoleaf-area ratio (F) and net assimilation rate (E). High ratesof nitrogen diminished the effects of competition on relativeleaf growth-rate, F, and on fresh-weight/dry-weight ratios,indicating competition for nitrogen, but high rates of potassiumdiminished only its effect on relative growth-rate of the crown,suggesting that competition for potassium had only a small effect. Competition depressed leaf nitrogen and potassium percentagesand total nitrogen and potassium uptake by the whole plant,but the depressions were small at high rates of nutrient supply,suggesting that the amounts of nitrogen and potassium availablewere nearly adequate for both sugar-beet and A. repens. When total dry weights and leaf areas of sugar-beet were comparedwith corresponding nutrient contents, variation in nitrogencontent alone could account for most of the effects of competitionon growth, but potassium depletion probably also contributeda little. E was correlated with potassium, but not nitrogen,per unit leaf area, but potassium differences could not adequatelyaccount for the effects of competition on E. Competition for potassium produced small effects compared withcompetition for nitrogen, in spite of large responses to addedpotassium, perhaps because potassium moves less readily in thesoil.     

Variations with Age in Net Assimilation Rate and other Growth Attributes of Sugar-beet, Potato, and Barley in a Controlled Environment: With two Figures in the Text

Sugar-beet, potato, and barley plants were grown in a controlledenvironment, for periods of up to 10 weeks from sowing, witha light intensity of 1,8oo f.c. (4·9 cal./cm.²/hr.) anda temperature of 20° C. during the 18-hour photoperiod and15° C. during the dark period, to test whether net assimilationrate varied with age and differed between the three species. Net assimilation rate of all species based on leaf area (E_A)fell approximately linearly with time. During 5 weeks E_A ofsugar-beet decreased by only about 20 per cent. and E_A of potatodecreased by 50 per cent. E_A of barley remained approximatelyconstant for 4 weeks after sowing and was halved during thesubsequent 4 weeks. The average value of E_A for all times wasgreatest for sugarbeet and least for barley. Net assimilation rates based on leaf weight (E_W) and leaf N(E_N) decreased at about 15 per cent. of the initial value perweek for all species; this was similar to the mean rate of decreaseof E_A of potato and barley, but greater than that of E_A of sugar-beet.Mean values of E_W or E_N for potato and barley were similar andless than for sugar-beet. Relative growth rate (R_W), relative leaf growth-rate (R_A), andleaf-area ratio (F) fell with time at similar rates for allspecies. Average values of R_W decreased and of F increased inthe order sugar-beet, potato, barley. R_A was greatest for potatoand least for barley.     

Effects of Temperature Variation at Different Times on Growth and Yield of Sugar Beet and Barley

Sugar-beet and barley were grown in pots outdoors (environmentN) and, for five successive 4-week periods starting at sowing,batches of plants were transferred to three growth rooms whosetemperatures were either similar to the outdoor mean (environment^M), or 3° C hotter (environment H) or 3° C colder (environmentC). Some plants were harvested immediately after treatment;others were returned to environment N and harvested when mature. At the end of period 1, sugar-beet plants from environment Mhad more dry weight and leaf area than those outdoors. Immediatelyafter spending later periods in environment M, plants had smallerleaves and similar dry weight to those continuously outdoors.These differences disappeared by maturity. Warmth in the growthrooms (i.e. the difference H—C) during periods 1, 2, and3, while leaf area was increasing, increased the number andsize of leaves and usually also dry weight; in later periodsit had no effect. The effects induced during periods 2 and 3,but not period 1, persisted to maturity to give greater totaland root dry weight and yield of sugar. The final effects ondry weight were much larger than those immediately after treatment,and were the result of differences in growth outdoors aftertreatment which depended on differences in leaf area; the efficiencyof the leaves was not affected by previous treatment. Transferring barley to environment M from N had inconsistentimmediate effects on leaf area and dry weight which disappearedby the final harvest. Transfer during periods 2 and 3, beforethe ears had started emerging, increased shoot number and delayeddevelopment. The proportion of the ears that ripened and theyield of grain were usually less for plants that had spent aperiod in environment M than for plants permanently outdoors,which also had some green ears. Warmth in the growth rooms duringperiods 1 and 2 increased dry weight and leaf area immediately,but had negligible effects at maturity because the increasesin leaf area did not persist after ear emergence. Warmth laterhastened death of leaves, decreased total dry weight immediatelyand also at maturity, but increased the proportion of ears thatripened and hence usually grain weight. Variation in leaf areaduration after ear emergence (D), determined by effects on thetime the ears emerged and the rate the leaves died, accountedfor most of the variation in grain yield, but warmth after theears emerged decreased grain yield less than proportionallyto the decrease in D. Net assimilation rate (E) of sugar-beet was greater than ofbarley, and decreased less with age. E of both species was usuallygreater in environment M than outdoors in spite of less radiation.It was only slightly affected by temperature. Nitrogen and potassium uptake were increased by treatments thatincreased dry weight. The percentage contents suggest that extrauptake was a consequence and not a cause of the increase indry weight.     

Light Distribution and Photosynthesis in Field Crops

In a new model of light distribution in field crops a parameters is the fraction of light passing through unit leaf layer withoutinterception. Radiation profiles measured with solarimetersand photocells give values of s from 0.7 for grasses to 0.4for species with prostrate leaves. Knowing s, leaf transmissionT and leaf-area index L the light distribution in a field cropmay be described by a binomial expansion of the form {s+(I-s)T)^L.To calculate crop photosynthesis at given light intensity thisexpansion is combined with two parameters describing the shapeof the light-response curve of single leaves. Finally, the assumptionthat solar radiation varies sinusoidally allows daily totalphotosynthesis to be estimated from daylength and insolation. The theory predicts about the same potential photosynthesisin a cloudy temperte climate with long days as in a more sunnyequatorial climate with short days. When L < 3 photosynthesisincreases as s decreases, i.e. as leaves become more prostrate;but when L > 5, photosynthesis increases as s increases,i. e. as leaves become more erect. Assuming that respirationis proportional to leaf area, estimated dry-matter productionagrees well with field measurements on sugar-beet, sugar-cane,kale, and subterranean clover. Estimates of maximum gross photosynthesis(for sugar-cane and maize) range from 60 to 9 g m^–2 day^–1depending on insolation.     

An Analysis of Growth of Oil Palms under Nursery Conditions: II. The Effect of Spacing and Season on Growth

Three experiments on the growth of watered nursery oil palmsare described, the results of which provide estimates of seasonalvariation in net assimilation rate (E_A) and relative growth-rate(R_w) in the tropics (6° 33' N.). The range of values obtained for E_A and R_w is similar to thatfound with seedlings and during early growth in the nursery(E_A = o.I8–o.32 g/dm²/week, R_w= o.84–I.70 per cent/day)and there is very little effect of season on E_A; such variationas exists appears to be related to solar radiation. A spacing experiment indicated that E_A is independent of leafarea index (L) when L is below about 2.2, but that above thislevel E_A decreases with increasing L, falling to zero at L =5.4. The crop growth-rate (C) is maximal when L is between 2.5and 3, the maximum value observed was o.62 g/dm²/week (equivalentto 3.22 x10⁴ kg/ha/annum). These results are compared with other estimates of growth andassimilation rates of seedling, nursery and adult oil palms,and are discussed in relation to the efficiency of energy fixation,and apparent growth-rates.     

An analysis of leaf growth in sugar beet.

The increase of leaf area index (L) was examined in a series of sugar-beet crops grown on different sites (Broom's Barn, Suffolk and Trefloyne, Dyfed) or with different husbandry treatments (sowing dates and nitrogen rates) between 1978 and 1982. The development of L could be described as a function of thermal time using three parameters; D_E, which was essentially an estimate of the thermal time required for crop establishment, and rH_L and D_L, the thermal rate and duration, respectively, of the increase of L. Variations in D_E between seasons and with sowing date were small, but significant; they were attributed to factors affecting the condition of the seedbed. There were much larger variations in rH_L, especially between seasons, sites and crops given different rates of nitrogen fertiliser, and there was a strong negative relationship between rH_L and D_L. Much of the variation in rH_L was associated with differences in the concentrations of nitrogen in the lamina dry matter. Faster rates for rH_L at Trefloyne than at Broom's Barn, and in the crop grown in 1982 as compared with other years, were also partly attributable to particularly warm conditions during the early development of some of the larger, faster-growing leaves within the canopy. The wider application of the relationships established from these experiments was tested with data from a series of crops grown on other sites between 1960 and 1962. The relationships held particularly well for beet grown on soils with high water-holding capacity but not for those on soils of low water-holding capacity.     

The Relation Between the Nitrogen Concentration and Photosynthetic Capacity of Potato (Solanum tuberosum L.) Leaves

Measurements of the rate of light-saturated photosynthesis (P_max)were made on terminal leaflets of potato plants growing in cropssupplied with 0, 3, 6, 12, 24 and 36 g N m^–2. Measurementswere made between 100 and 154 d after planting. Two types ofleaf were selected—the fourth leaf on the second-levelbranch (L₄, _B1) and the youngest terminal leaflet that was measurable(L_YM). Later, the total nitrogen concentration of each leaflet(N_L) was measured. A linear regression between P_max and N_L,common to both leaf positions, explained 68.5% of the totalvariation. With L₄, _B1 leaves there was a significant improvementin the proportion of variation explained when regressions withseparate intercepts and a common slope were fitted to individualfertilizer treatments. These results suggest that an increasingproportion of leaf nitrogen was not associated with the performanceof the photosynthetic system with increasing nitrogen supply.This separation between nitrogen treatments was not as clearfor L_YM leaves. Stomatal conductance to transfer of water vapourwas neither influenced by leaf position nor directly by nitrogensupply. Rather conductance declined in parallel with the declinein photosynthetic capacity. Solanum tuberosum, potato, nitrogen, photosynthesis, stomatal conductance, leaf     

Some factors affecting germination of Peronospora farinosa conidia in water

The germination of conidia of Peronospora farinosa f. sp. betae, collected from sugar beet and suspended in deionized water, was inhibited by dilution with 10% solutions of glycerol, glucose or sucrose and with sap from sugar-beet leaves. Germination was stimulated by diluting with deionized water but not with tap water or biological saline. Substances that diffused from excised buds of sugar-beet plants into deionized water also stimulated germination of conidia but diffusates from leaves did not. This may partly explain why buds are more susceptible to downy mildew than leaves in sugar beet. Germination of conidia was apparently stimulated more by diffusates from buds of seedlings than by those from buds of older plants; this may help to explain why sugar-beet seedlings are more susceptible to downy mildew than older plants. Diffusates from plants of four sugar-beet stocks, that differed from each other in susceptibility to downy mildew, had very similar effects on germination of P. farinosa conidia. Stimulation of spore germination on the surfaces of buds and leaves did not seem, therefore, to be an important factor in determining resistance or susceptibility to downy mildew in these stocks.     

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.     

STUDIES ON THE IMPORTANCE OF WILD BEET AS A SOURCE OF PATHOGENS FOR THE SUGAR-BEET CROP

Beet yellows virus, beet mosaic virus, rust ( Uromyces betae (Pers) Lév.), and downy mildew ( Peronospora schachtii Fuckel.) were found to be common in wild beet ( Beta vulgaris s.-sp. maritima L.) growing on the foreshores of south Wales and southern England. The virus diseases were more prevalent in southeast England than in the west, rust more in the west than in the east, and downy mildew is equally prevalent in all regions.
Beet yellows is the most commercially important disease and is more common in sugar-beet crops in East Anglia than elsewhere in Great Britain. There was no evidence that beet yellows spread in East Anglia from wild beet to nearby sugar-beet crops during the springs of 1958 or 1959, and Myzus persicae Sulz., the principal vector of yellows, was rarely found on wild beet growing on the foreshore.
In glasshouse experiments aphids colonized sugar-beet plants watered with tap water in preference to those watered with sea water. Daily watering with sea water made plants unpalatable to aphids within 14 days. Aphids also preferred leaves sprayed with distilled water to those that had been sprayed with sea water. Salt solutions gave results similar to those obtained with sea water.     

Some factors affecting the concentrations of sugars in leaves of inbred sugar-beet lines

In the glasshouse, large differences in concentrations of glucose and sucrose were observed between leaves of inbred sugar-beet lines that are known to differ from each other in resistance to pests and diseases. Differences between these lines in concentrations of fructose, glucose and sucrose were more pronounced in the petiole than in the lamina. The concentrations of glucose and fructose were lower in the first two leaves (primary leaves) than in those produced subsequently (secondary leaves); both types of leaf contained similar concentrations of sucrose. Secondary leaves from plants that had been kept in darkness for 17 h contained less fructose, glucose and sucrose than those of plants kept in sunlight for 5 h. Longer period of darkness lowered the concentrations of monosaccharides in the leaves further but did not affect the sucrose content. Primary and secondary leaves from the same sugar-beet plant often differ in non-race-specific resistance to pests and diseases; and darkness can affect suscetibility of beet to downy mildew and to the aphid Myzus persicae. The results of the sugar determinations therefore support the hypothesis that the concentrations of certain carbohydrates in sugar-beet leaves are important in non-race-specific resistance to pests and diseases.     

Rooted leaves for physiological experiments

Summary Rooted leaves provide convenient material for investigating various physiological processes. Details are given for producing rooted leaves of species with tuberous roots, e.g. Sweet potato (Ipomoea batatas) and Dahlia (Dahlia variabilis) and species with tap roots, e.g. Sugar beet (Beta vulgaris) and Runner bean (Phaseolus coccineus). The storage root formed on a single sugar-beet leaf develops concentric cambia suggesting that their formation is not determined by particular leaves.     

Testing 'Economy in Design' in Plants: are the Petioles and Rachises of Leaves 'Designed' According to the Principle of Uniform Strength?

Fifteen petioles and rachises from three dicotyledon species(Acer saccharum, A. negundo, and Aesculus hippocastanum), apalm (Chamaedorea erumpens), and a fern (Cyrtomium falcatum)were used to test the hypothesis of 'economy in design' in termsof the design principle of uniform strength, i.e. a beam inwhich the section modulus (Z) varies along beam-length (L) inthe same proportion as the bending moment (M). Such a beam is'economical' regarding the amount of material used in its 'construction'because each of its cross section has the minimum transversearea required to satisfy the conditions of strength. The extentto which the morphology of a petiole or rachis conformed withthis design principle was initially evaluated by normalizingZ (measured at a distance, x, from the tip of a petiole or rachis)with respect to the magnitude of Z measured at the base of thepetiole. The normalized values were plotted against normalizedpetiole-rachis length (x/L). The design principle was judgedto be demonstrated when such a plot was found to be isometric,i.e. when the plot had a slope of unity. This procedure wastested further by plotting M/Z vs. x/L for representative leavesof C. erumpens and A. saccharum, and judged adequate. The allometriesof all six simple/palmate leaves were found not agree with thedesign principle. The taperings of nine petioles and rachisesfrom pinnate leaves were consistent with the design principle.This was interpreted to provide circumstantial evidence for'economy in design' in the petioles of some pinnate leaves andevidence that the mechanical 'design' of the petioles of somesimple/palmate leaves differs substantially from that of pinnateleaves.Copyright 1993, 1999 Academic Press Leaf biomechanics, plant adaptation, petioles, rachises     

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     

Genetic diversity and gene flow between wild, cultivated and weedy forms of Beta vulgaris L. (Chenopodiaceae), assessed by RFLP and microsatellite markers

 Beets belonging to the species Beta vulgaris L. can be found in crop, wild and weedy forms, all of which are interfertile. We studied the intra-specific genetic relationships of about 300 individuals from 54 populations of various French geographic origins using nuclear molecular markers (five single-copy RFLP loci and one microsatellite locus). The patterns of diversity were congruent for both types of markers. Genetic diversity in wild beets appeared to be high, both in term of allele number and observed heterozygosity, whereas the narrowness of the cultivated-beet gene pool was confirmed. Genetic distances between all forms showed that weed beets in northern France are intermediates between sugar beet and inland wild beets in south-western France. This analysis allowed us to infer the paternal origin of weed beets and furthermore, is in agreement with a previous study which focused on their maternal origin: weed beet infesting sugar-beet fields originated from accidental and recurrent hybridization between cultivated lines and ruderal inland wild beets during the production of commercial seeds in south-western France. Inland wild beets are genetically close to Mediterranean coastal wild beets, but differ from other coastal forms (from Biscay, Brittany and northern France). The study of gene flow in the beet complex contributes to the risk assessment of transgenic beets. Received: 8 June 1998 / Accepted: 8 October 1998     

植物金属硫蛋白Ⅱ型与谷胱甘肽在烟草中的表达和合成特性

利用从印度芥菜(Brassica juncea)中获得的金属硫蛋白2型（BjMT2）基因通过农杆菌介导法转入模式植物种烟草中。转基因烟草在经过继代组织培养和抗生素筛选以及PCR和Western blot检测后,确定目的基因BjMT-2被整合到烟草基因组中并具备表达功能。与对照野生型相比,转入金属硫蛋白2型的烟草在植物形态和根部发育方面都发生了显著的性状变化。在正常条件下,转基因植物叶片组织中谷胱甘肽的含量与野生型没有明显差别,但经过100 mmol·L^-1 Cu²⁺胁迫后,谷胱甘肽的含量明显高于野生型。在转基因植物细胞膜系统中V-型ATP酶的活性低于野生型,而P-型ATP酶的活性则表现出明显的升高趋势。     

Biomechanical Attributes of the Leaves of Pine Species

The flexural stiffness EI, elastic modulus E, second momentof area I, length L, and weight Wt of foliage leaves from 26species of pine were measured to determine the manner in whichEI is scaled to leaf size (L or Wt, or both) and to determineif the biomechanical attributes of foliage leaves could be juxtaposedwith the systematic affiliations of species within Pinus Biomechamcaland morphometric data were explored based on a model from engineeringtheory that predicts the relationships among EI, Wt and L providedthat the maximum tip-deflection _max of an untapered cantileveredbeam sustaining its own weight is maintained as the beam eitherincreases in length or weight, or both, I e _max = Wt L²/8EIThe data show that EI disproportionately increased as eitherWt or L, or both increased The allometry of leaves did not conformto that predicted by the model Rather, EI was proportional tothe product of Wt and L raised to an exponent slightly greaterthan one Thus, Omax was predicted not to be maintained as eitherWt or L, or both, increased, as verified by observations Therelationship between El and Wt(L) differed for species typicallyproducing two leaves per fascicle and those bearing more thantwo leaves per fascicle Also, El is geometrically constrainedby the number of leaves produced per fascicle, principally interms of the effects of the number of leaves per fascicle onI Pinus, pine, leaves, biomechanics, Young's modulus     

The Influence of Removing Tubers on Dry-matter Production and Net Assimilation Rate of Potato Plants

To study the effect of removing tubers on growth and net assimilationrate (E) of potato, plants were grown in pots partly filledwith soil with the shoot growing through a polythene cover.Tubers developed in the space between the cover and the soilsurface. Removing tubers immediately they began to form had little effecton E at the beginning of the experiment but later greatly reducedit. Shading reduced E more at the beginning of the experimentthan later. Removing tubers decreased total dry weight, butmuch of the material that would have moved to tubers accumulatedin leaves and stems. In intact plants the loss of weight byshading was mainly from the tubers; in plants without tubersit was mainly from stems and leaves. Removing tubers increasedleaves on lateral stems. Increasing the amount of nitrogen supplieddiminished the effect on E of removing tubers, presumably becausethe extra allowed other sinks for carbohydrate to develop. Thegrowth of some buds of the potato plant is so strongly inhibitedthat they cannot grow and act as sinks for excess carbohydratewhen tubers are removed. Such internal inhibition of growthmay sometimes suffice to influence the magnitude of E of normalplants. Removing tubers usually increased sugar and starch contentand protein N content of stems and leaves.     

Comparative Leaf Epidermal Anatomy of Mutants of Barley (Hordeum vulgare L. 'Himalaya') which Differ in Leaf Length

We wished to determine the nature of differences in epidermalcell numbers and dimensions between leaves of different lengthin mutants of barley (Hordeum vulgare L. ‘Himalaya’).Three comparisons were made: leaf one (L1)vs. leaf four (L4);wild typevs. nine dwarf mutants and wild typevs. a slender mutant.L1 was shorter than L4, and for most lines this was associatedwith a change in epidermal cell number for the blade, and inboth cell number and length for the sheath. Compared to wildtype, the smaller leaves of dwarf plants generally had shorterand fewer cells in both blade and sheath. The blade of slenderplants was the same length (L1) or longer (L4) than wild type,while the sheath was longer than that of wild type for bothL1 and L4. Slender plants had longer but fewer cells than thewild type along the blade of L1, and shorter but more cellsfor the blade of L4. In the sheath, slender plants had longerand more (L1) or fewer (L4) cells than did the wild type. ForL1, variation in blade width amongst the barley lines was associatedwith a change in file width and file number. For L4, blade widthvaried only with file number, except for slender plants wherenarrow blades were associated with reduced file width. Hencethere was no consistent correlation between changes in cellsize or cell (or file) number with changes in leaf length orwidth. Differences depended on the leaf (L1vs. L4), leaf part(bladevs. sheath), and the nature of the mutation (dwarfvs.slender). Barley (Hordeum vulgare L. ‘Himalaya’); leaf epidermis; dwarf mutant; slender mutant