Growth Rate, Photosynthesis and Respiration in Relation to Leaf Area Index

This work examined three possible explanations of growth rateresponses to leaf area index (LAI) in which growth rate perunit of ground area (crop growth rate, CGR) increased to a plateaurather than decreasing above an optimum LAI at which all lightwas intercepted. Single leaf photosynthetic measurements, andwhole plant 24 h photosynthesis and respiration measurementswere made for isolated plants and plants in stands using Amaranlhushybridus, Chenopodium album, and two cultivars of Glycine maxgrown at 500 and 1000 µimol m^–2 S^–1 photosyntheticphoton flux density at 25 °C. CGR, relative growth rate(RGR), and LAI were determined from 24 h carbon dioxide exchangeand leaf area and biomass measurements. Respiration increasedrelative to photosynthesis with crowding in A. hybridus andthere was an optimum LAI for CGR. In contrast, the ratio ofrespiration to photosynthesis was constant across plant arrangementin the other species and they had a plateau response of CGRto LAI. Neither increased leaf photosynthetic capacity at highLAI nor a large change in biomass compared to the change inLAI could account for the plateau responses. It was calculatedthat maintenance respiration per unit of biomass decreased withdecreasing RGR in C. album and G. max, but not A. hybridus,and accounted for the plateau response of CGR to LAI. Sincesimilar decreases in maintenance respiration per biomass atlow RGR have been reported for several other species, a constantratio of respiration to photosynthesis may occur in more speciesthan constant maintenance respiration per unit of biomass. Amaranlhus hybridus L., Chenopodium album L., Glycine max L Merr, soybean, photosynthesis, respiration, growth, leaf area index     

Effect of aqueous leaf extract of common lambsquarters (Chenopodium album L.) and NaCl on germination and seedling growth of rice

Aqucous leaf extract of common lambsquarters (Chenopodium album L.) was evaluated alone or in combination with NaCl for its effect on germination and rice seedling growth. The treatments have no effect on germination. However, growth of both shoot and root significantly decreased under NaCl alone and in combination with leaf extract. Root growth was affected more than the shoot and the effect of NaCl was accentuated in the presence of leaf extract.     

A Vertical Gradient of the Chloroplast Abundance among Leaves of Chenopodium album

The abundances of chloroplasts in leaves on the main stems ofChenopodium album at different height levels were investigatedin relation to the photosynthetic capacity and light environmentof the leaves. (1) The number of chloroplasts per mesophyllcell decreased with descending position of leaves, except foryoung developing leaves at the top of plants that had smallerchloroplast numbers per cell than matured leaves beneath them.Contents of chlorophyll and ribulose-1,5-bisphosphate carboxylase/oxygenaseper leaf area that were highest in the topmost young leavesand decreased with decreasing height level indicate that thereis a vertical gradient of chloroplast abundance per leaf areadecreasing from the top of the leaf canopy with depth. (2) Light-saturatingrate of photosynthetic oxygen evolution per leaf area of maturedleaves decreased more steeply with decreasing leaf positionthan the chloroplast number per cell. Gradients of chlorophylland the enzyme protein contents were also steeper than thatof the chloroplast number. Loss of photosynthesis in lower leavesis, therefore, ascribed partly to loss of whole chloroplastsand partly to reduced photosynthetic capacities of the remainingchloroplasts. (3) The chloroplast number per cell in newly expandedsecond leaves was comparable to those in leaves that have developedat later stages of the plant growth but decreased graduallyduring leaf senescence both in the dark and light. The formationof the vertical gradient of chloroplast abundance is, therefore,ascribed to loss of whole chloroplasts during senescence ofleaves. (4) Irradiance a leaf receives decreased sharply fromthe top of the canopy with depth. The physiological or ecophysiologicalsignificance of the vertical distribution of chloroplasts amongleaves was discussed taking light environments of leaves intoconsideration. (Received July 31, 1995; Accepted October 20, 1995)     

Reduction of Nitrate and Nitrite in Lambsquarters (Chenopodium album) Biotypes Resistant and Susceptible to Atrazine Toxicity

The nitrite-reducing activity of the normal susceptible biotype of lambsquarters (Chenopodium album L.) was strongly inhibited by atrazine in the assay medium, both in the case of the in vivo assays of leaf discs in light, and in vitro photoreduction assays of crude extracts. In vitro assays of crude extracts with methylviologen or ferredoxin supplying the reducing potential were not inhibited by atrazine. In the resistant biotype, inhibition of nitrite reduction did not occur with any of the above assays. Thus, it appears that atrazine does not inhibit nitrite reductase itself, but rather the availability of photosynthetically supplied electrons for the reduction. Atrazine had no effect when added to the media for either in vivo or in vitro assays of nitrate reduction by either the susceptible or resistant biotype.     

Architecture and growth of an annual plant <Emphasis Type="Italic">Chenopodium album</Emphasis> in different light climates

Light climates strongly influence plant architecture and mass allocation. Using the metamer concept, we quantitatively described branching architecture and growth of Chenopodium album plants grown solitarily or in a dense stand. Metamer is a unit of plant construction that is composed of an internode and the upper node with a leaf and a subtended axillary bud. The number of metamers on the main-axis stem increased with plant growth, but did not differ between solitary and dense-stand plants. Solitary plants had shorter thicker internodes with branches larger in size and number than the plant in the dense stand. Leaf area on the main stem was not different. Larger leaf area in solitary plants was due to a larger number of leaves on branches. Leaf mass per area (LMA) was higher in solitary plants. It did not significantly differ between the main axis and branches in solitary plants, whereas in the dense stand it was smaller on branches. Dry mass was allocated most to leaves in solitary plants and to stems in the dense stand in vegetative growth. Reproductive allocation was not significantly different. Branch/main stem mass ratio was higher in solitary than dense-stand plants, and leaf/stem mass ratio higher in branches than in the main axis. Nitrogen use efficiency (NUE) (dry mass growth per unit N uptake) was higher and light use efficiency (LUE) (dry mass growth per unit light interception) was lower in the plant grown solitarily than in the dense stand.     

The Effect of Rooting Space on Whole Plant and Leaf Growth in Brussels Sprouts (Brassica oleracea var. gemmifera)

Seedlings of Brassica oleracea var. gemmifera DC. (Brusselssprouts) were grown in four pot sizes over a 4-week period.Whole plant, stem, root and foliage d. wts and foliage area,together with specific leaf area, leaf area ratio and numberof leaves initiated were reduced by restricting rooting space.Individual leaves showed similar reductions in d. wt and area,with the effect being more pronounced in later-formed leaves.Cell counts and measurements on the epidermis and palisade mesophylllayers of the first four leaves showed that the reduction ingrowth was due to reduced cell division. Cell numbers in thefirst-formed leaf were halved over the range of pot sizes used,and there was a progressively greater reduction in cell numbersin later-formed leaves. There was some tendency for cell sizeto decrease with decreasing rooting space, but this was notgeneral and was most marked between plants grown in the twosmallest pot sizes. Brassica oleracea var. gemmifera, Brussels sprouts, rooting space, growth analysis, leaf growth, cell numbers, cell sizes     

Effects of Plant Density on Frequency Distributions of Plant Height in Chenopodium album Stands: Analysis Based on Continuous Monitoring of Height-growth of Individual Plants

Height-growth of individual plants of Chenopodium album in even-agedmonospecific stands with initial densities of 400, 800, and3600 plants m^-2 was followed from emergence to fruit maturationto elucidate the factors responsible for size hierarchy formation.Many individuals stopped growing rather abruptly at relativelyearly stages in the vegetative phase and some of them eventuallydied. The other plants grew until fruit maturation and attainedlarge final heights. Depending on whether they terminated orcontinued height-growth during the vegetative phase, the plantswere called 'lower' and 'upper' plants. The numbers of the 'upper' plants per unit area were about 100plants m^-2 irrespective of the initial plant densities, andthus the number of 'lower' plants increased with the increasein the plant density. However, there was an upper limit to thenumber of the surviving 'lower' plants (400-700 plants m^-2).The shapes of the final frequency distributions of plant heightwere largely determined by the ratio of the number of 'upper'plants to that of surviving 'lower' plants, and were bimodalfor the 400 plants m^-2 plot and L-shaped for the 800 and 3600plants m^-2 plots. From these, it is concluded that the segregationof the plants into 'upper' and 'lower' plants is an essentialfactor responsible for the size hierarchy formation. The presentresults also indicate that both bimodal and L-shaped distributionscan result from one-sided competition for light, depending onthe initial plant densities.Copyright 1995, 1999 Academic Press Chenopodium album L., fat hen, height-growth, height-size structure, bimodal distribution, L-shaped distribution, one-sided competition     

Low resistance against novel 2-benzylamino-1,3,5-triazine herbicides in atrazine-resistant Chenopodium album plants

The effects of nine novel 2-benzylamino-1,3,5-triazines on photosynthetic reactions were measured in thylakoids isolated from wild-type and atrazine-resistant plants of Chenopodium album. The resistant plants have a mutation of serine for glycine at position 264 of the D1 protein. The measurement of oxygen evolution and chlorophyll a fluorescence induction indicated a 2–4-fold stronger inhibition by the 6-trifluoromethyl analogues of Photosystem II-dependent electron flow than atrazine. Analogues having a 6-methyl-, 6-monofluoromethyl or 6-difluoromethyl substitution were weak inhibitors, indicating that the 6-trifluoro group is very important for strong inhibition. All the nine novel 2-benzylamino-1,3,5-triazines were almost as active in wild-type as in atrazine-resistant thylakoids, indicating that the benzylamino substitution may be important for the lack of resistance in the atrazine-resistant plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of aqueous leaf extract of common lambsquarters and NaCl salinity on the germination, growth, and nutrient content of wheat

Aqueous leaf extract of common lambsquarters (Chenopodium album L.) was evaluated alone or in combination with NaCl salinity for its influence on germination, seedling growth and contents of Na, K, and Ca by shoots and roots of wheat. The leaf extract and NaCl alone or in combination did not have any significant effect on germination, but the shoot and root lengths of seedlings and their dry weight decreased significantly by the treatments. Root growth was affected more than the shoot. The combination of leaf extract and NaCl drastically reduced the growth more than the separate effects of these stress treatments. The incorporation of leaf extract in the growth media decreased the content of Na by shoot, whereas the contents of K and Ca increased. NaCl treatments in combination with leaf extract increased the content of Na. Similar increases were observed for K and Ca in shoot, while these nutrients were increased in roots compared to control.     

The Processes of Height-rank Determination Among Individuals and Neighbourhood Effects inChenopodium albumL. Stands

The height ofChenopodium albumL. plants grown in monocultureat three different densities was followed throughout the growingseason to examine size-rank determination processes with specialreference to the effects of neighbourhood conditions. Changesin height rank of plants in the stands were assessed by therank correlation between final height and the height at eachmeasurement during the growing season. The height ranks of plantswere almost fixed 1–2 weeks after canopy closure whenthe stand height was 10–20% of final stand height, andfixation occurred earlier in the denser plot. At each measurement,the effects of neighbourhood were evaluated as the partial correlationcoefficient between height growth and neighbourhood index withheight held constant (r_GN.H), in which competitive asymmetrywas incorporated. During the early period of the growing season,r_GN.Hwasnon-significant or positive (plants with taller and/or closerneighbours elongated faster), indicating no local competition.Just after canopy closure,r_GN.Hbecame negative, indicating localcompetition. A plant's rank changed only in an initial shortperiod of the competition. Plants occupying the upper canopyof stands at the end of the growing season were distinguishedby greater height growth during the initial short period ofcompetition after canopy closure, although these plants werenot necessarily taller before the onset of local competition.These results suggest that the fate of a plant in a crowdedstand is determined in the early stage of stand development.Copyright1999 Annals of Botany Company Height growth, neighbourhood competition, local competition, height-rank of plants in population, size difference, asymmetric competition,Chenopodium albumL.     

Temperature and Water Relations for Sun and Shade Leaves of a Desert Broadleaf, Hyptis emoryi

The temperature and water relations of sun versus shade leavesof Hyptis emoryi Torr. were evaluated from field measurementsmade in late summer. Throughout most of the day sun leaves hadhigher temperatures and higher resistances to water vapour diffusion,but lower transpiration rates and lower stem water potentials,than did shade leaves. Leaf absorptivity to solar irradiationwas less for 1.5-cm-long sun leaves (0.44) than for 4.0-cm shadeleaves (0.56). For both leaf types the stomatal resistance increasedas the water vapour concentration drop from the leaf to theair increased. Energy balance equations were used together with the measuredtemperature dependence of photosynthesis to predict the effectof variations in leaf absorptivity, length, and resistance onnet photosynthesis. The influence of leaf dimorphism on wholeplants was determined by calculating daily photosynthesis andtranspiration for plants with various percentages of sun andshade leaves. A hypothetical plant with all sun leaves in thesun had about twice the photosynthesis and half the transpirationratio as did plants with sun leaves in the shade or shade leavesin the sun or shade. Plants with both sun and shade leaves hadthe highest predicted photosynthesis per unit ground area. Thepossible adaptive significance of the seasonal variation insun and shade leaf percentages observed for individual H. emoryibushes is discussed in terms of water economy and photosynthesi     

Leaf Ecology of Pre-reproductive Ontogenetic Stages of the Palm TreeEuterpe edulisMart. (Arecaceae)

We studied leaves of 208 seedlings (S), infants (I) and juveniles(J) ofEuterpe edulis,randomly selected from plants in 1 ha ofswampy forest in SE Brazil. Each new leaf began extending afterthe complete development of the preceding leaf. The sequencesteps of leaf growth were emergence, linear growth while closed,opening of segments and logarithmic growth of the petiole. Averageleaf production rate (2.21 leaves per plant year^-1) did notvary among ontogenetic stages, conforming to a plastochronicrhythm. Average linear growth rate of the closed leaf was directlyrelated to average area of the open lamina. Herbivores attacked33.0% of all leaves giving rise to up to 10% loss of area andincluded damping-off-inducing suckers (7.1%), ordinary suckers(9.8%), chewers (5.4%), miners (2.7%) and multiple attacks (8.0%).These attacks varied among stages (S=22.4%, I=38.1%, J=33.3%),as did leaf mortality rates (S=26.5%, I=14.3% and J=0.0%). Unknownfactors were the main cause of leaf mortality (S=14.3%, I=7.1%).Not losing a leaf while a seedling and attaining a minimum leafarea in the infant stage were critical events for survival.Plants gained leaf area by not losing leaves while a seedling,by producing larger leaves with greater growth rates, and byaccumulating leaves with longer lifespans. The petiole can simulatean energetically cheaper branch, delimit a vital space aroundthe stem, favourably position the leaf lamina and substituteprovisionally for stem growth in height.Copyright 1999 Annalsof Botany Company Arecaceae,Euterpe edulis, herbivory, leaf ecology, leaf growth, leaf production, semideciduous forest, southeastern Brazil.     

Isolation of a factor stimulatory to Bradyrhizobium japonicum in broth culture

Previous experiments indicated that water extracts of lambsquarters (Chenopodium album) and green foxtail (Setaria viridis), among others, stimulated growth of Bradyrhizobium japonicum in broth culture. Water extracts of lambsquarters shoots collected before or after anthesis were equally stimulatory. The stimulatory effect of extracts of lambsquarters when heated to 100°C for 30 min or autoclaved for 15 min was reduced by about 20% compared to untreated extracts. Extracts of green foxtail were less affected by higher temperature under similar conditions. Extracts of both green foxtail and lambsquarters completely lost their stimulatory effect following exposure to aerial microflora for 120 h. Water extract of lambsquarters shoots was more stimulatory than methanol extract, and neither ether nor butanol extracts resulted in stimulation. Both shoots and roots of lambsquarters and green foxtail were sequentially extracted first by water followed by methanol and vice-versa. The bioassay of these extracts indicated that there could be two components of the growth factor-one, larger component is soluble in water, the other, smaller component is soluble in methanol. After fractionation of the crude aqueous extract of lambsquarters shoots by four organic solvents, the residual aqueous extract retained the growth factor. Dialysis of the residual aqueous extract of lambsquarters shoots through a membrane (MWCO 1000) indicated that the molecular weight of the growth factor was less than 1000. The fraction having molecular weight <1000 was separated by paper chromatography using 6% acetic acid as developer. The fraction with Rf 0.91 showed the highest stimulation of the bacterium.     

Photosynthetic Determinants of Growth in Maize Plants: Effects of Nitrogen Nutrition on Growth, Carbon Fixation and Photochemical Features

Maize(Zea mays L.) plants were grown in a greenhouse with differentlevels of nitrate-N (2 to 20 millimolar). Nitrogen nutritionhad dramatic effects on plant growth and photosynthetic characteristicsof mature leaves. Increasing nitrogen resulted in greater biomassproduction, shoot/root ratios, and rates of leaf expansion duringthe day. The elongating zone of high-N plants had higher activities(per gram fresh weight) of sucrose synthase and neutral invertasethan low-N plants, suggesting that increased leaf growth wasrelated to a greater biochemical capacity for sucrose metabolism. Mature leaves of high-N plants had higher rates of photosynthesisand assimilate export (sucrose formation), and partitioned morecarbon into sucrose relative to starch. Increased photosyntheticrates (leaf area basis) were associated with higher levels ofribulose-l,5-bisphosphate carboxylase, phosphoenolpyruvate carboxylaseand pyruvate, phosphate dikinase (determined immunochemically).In addition, N-nutrition affected the functional organizationof chlorophyll in the leaves. Large increases in the numberof PS I reaction centers were observed which fully accountedfor increases in leaf chlorophyll content with increasing nitratesupply. Collectively, the results suggest that increased growth of maizeplants at high light and optimal nitrogen nutrition is relatedto greater capacity for photosynthesis and translocation inmature leaves, and possibly increased capacity for sucrose metabolismin expanding leaves. (Received May 22, 1989; Accepted August 28, 1989)     

Relationships between Height, Diameter and Weight Distributions of Chenopodium album Plants in Stands: Effects of Dimension and Allometry

Frequency distributions of height (H), stem diameter (D) anddry weight (W) of Chenopodium album plants in even-aged monoculturesat the initial plant densities of 400, 800 and 1200 plants m^-2(400-, 800- and 1200-plots) were compared. The height distributionsat the end of the growing season were bimodal for the 400-plotbut L-shaped for the 800- and 1200-plots. The distributionsof diameter and dry weight were L-shaped for all the plots.When the size measures were expressed on the log scale so asto eliminate effects of the differences in dimension, frequencydistributions of log W and log H for the 400-plot were bimodal.In contrast, the log D distributions were bell-shaped for allthe plots. To elucidate factors responsible for the differences in frequencydistributions among log size measures, we examined allometricrelationships between log size measures. They were all non-linearall non-linear mainly because the allometric relationships weremarkedly different between the plants forming the upper-mostleaf layer ('upper' plants) and the suppressed plants ('lower'plants). A striking feature was that the heights of the 'upper'plants were almost uniform in spite of their varied diameters.Continuous monitoring of growth of the individual plants inthe stand revealed that the height of the 'upper' plants becameuniform just after the canopy closure, at about 30 d after emergence,and that uniform growth in height of these plants continuedfor about 70 d until the end of the growing season. On the otherhand, growth of the suppressed 'lower' plants terminated atvarious stages before flowering. The 'height convergence' ofthe 'upper' plants was thus identified as a key factor for thesegregation of the plants into the two groups of distinctlydifferent allometries. Since the segregation of the plants into 'upper' and 'lower'plants was reflected in their dry weights, frequency distributionsof log W were similar to those of log H. The bell-shaped distributionsof log D were attributed to the overlapping of the diametersof slender 'upper' plants with those of larger 'lower' plants.Significance of 'height convergence' is discussed.Copyright1995, 1999 Academic Press Chenopodium album L., fat hen, height, size structure, bimodal distribution, L-shaped distribution, allometry, growth     

The Dynamics of Carbon Supply from Leaves of Barley Plants Grown in Long or Short Days

The role of the mature leaf in supplying carbon for growth inother parts of the plant was examined using a steady-rate ¹⁴CO₂labelling technique. The pattern of events occurring in theleaf during one complete 24 h cycle was compared in plants grownin, and adapted to long and short photoperiods. The rates ofleaf photosynthesis, night respiration and daytime loss of carbonfrom the growing regions of the plant Were similar in long orshort photoperiods. As a percentage of the total carbon fixedduring the photoperiod, total respiration was c. 50% for shortday plants but only 25% for long day plants. Thirty to forty per cent of the carbon fixed during the photoperiodwas retained in the leaf for export during darkness—therest was exported immediately. In leaves of short day plantssucrose and starch were the main form of the stored carbon.By the end of the dark period these compounds had been almostcompletely depleted. In leaves of long day plants there weremuch larger basal levels of sucrose and starch, upon which thediurnal variations were superimposed. These leaves also accumulatedfructosans. The delay in starch remobilization previously foundin leaves of short day plants was also evident in leaves oflong day plants even though large concentrations of sucroseand fructosans were present This suggests the presence of distinctpools of sucrose in the leaf.     

Regulation of Leaf Shape in the Solanifolia Mutant of Tomato (Lycopersicon esculentum) by Plant Growth Substances

The solanifolia mutant (sf/sf) of tomato (Lycopersicon esculentum)produces leaves consisting of leaflets with entire margins,unlike the lobed leaflets of normal plants. Normal plants treatedwith gibberellic acid (GA₃) produced leaves with entire marginswhereas mutant plants exposed to 2-chloroethyl-trimethyl ammoniumchloride (CCC)—an inhibitor of gibberellin biosynthesis—producedlobing of leaflets. The leaf area of the mutant was significantlygreater than that of the normal, but was not significantly differentfrom GA₃-treated normal leaves. Similarly, in CCC-treated mutantleaves the leaf area was not different from that of normal untreatedleaves. These observations suggest that the sf/sf mutation affectsthe leaf shape through its effect on endogenous gibberellinsand/or inhibitory substances. Leaf shape, Lycopersicon esculentum, plant growth substances, tomato     

The Effects of Shading and Cutting Treatments on the Photosynthetic Rate of Ryegrass Leaves

As the leaf area of miniature simulated swards of S24 perennialreygrass (Lolium perenne L.) grown in controlled environmentincreased, successive leaves which expanded on the main stemof a sample plant within the sward had progressively lower photosyntheticcapacities. When the plants surrounding the sample plant were cut, the photosyntheticcapacity of the next leaf to expand was increased, whether ornot other leaves on the sample plant had been removed. Whenall fully expanded leaves on the sample plant were removed butthe surrounding plants left uncut, the photosynthetic capacityof successive leaves on the sample plant continued to decreaseas in uncut swards. These results support the view that the changes in photosyntheticcapacity in grass swards are consequences of changes in thelight climate of the developing leaf rather than of changesin demand for assimilates or growth substance supply. The declinein photosynthetic capactiy was contributed to by both stomataland residual diffusion resistances.     

Accumulation and Partitioning of Dry Matter in Taro [Colocasia esculenta (L.) Schott]

A field study was conducted as part of an ongoing effort tocollect data on patterns of leaf area development and dry matteraccumulation and partitioning among various plant parts duringgrowth and development of two taro cultivars. Plants were harvestedfor biomass about every 6 weeks during the growing season. Ateach harvest, plants were separated into various plant parts,and their dry matter content was determined. The first 80 dafter planting were characterized by low rates of dry matteraccumulation, with only leaves, petioles, and roots showingsubstantial growth. Afterwards, increases in total dry matterwere mainly the result of corm and sucker growth. Corm bulkingoccurred after the attainment of maximal leaf area indices.The absence of an optimal leaf area index for a longer periodof time may have prevented the realization of higher dry matteryields. The partitioning of dry matter to the corms of bothcultivars remained almost constant especially after 150 d afterplanting. This process was in contrast to the partitioning ofdry matter to the suckers, which increased significantly untilthe end of the growing cycle.Copyright 1995, 1999 Academic Press Taro, Colocasia sp., growth, dry matter partitioning     

The Surface Structure of Leaves of Chenopodium album L.

Photomicrographs were used to study the surface structure ofleaves of Chenopodium album L. (fat hen). The leaves have asilvery bloom which is a layer of small, separate spheres ofaverage diameter 80 µ, transparent when turgid. Each globuleis attached to the leaf by a capillary stalk and movement studieswith eosin showed that they are linked by a continuous aqueouspathway. As leaves mature, the globules are less densely distributed;they collapse and are then readily detached from the surface.They contain inorganic material, silicates being a major constituent.They are stable to heat, cooling in liquid nitrogen or brieftreatment with chloroform or surfactants. Probably, the globulesare not entirely bounded by wax, and silicates may form a largepart of the outer walls.