Stages Of Leaf Development Research Articles

Changes in Chloroplast mRNA Stability during Leaf Development.

During spinach leaf development, chloroplast-encoded mRNAs accumulate to different steady-state levels. Their relative transcription rates alone, however, cannot account for the changes in mRNA amount. In this study, we examined the importance of mRNA stability for the regulation of plastid mRNA accumulation using an in vivo system to measure mRNA decay in intact leaves by inhibiting transcription with actinomycin D. Decay of psbA and rbcL mRNAs was assayed in young and mature leaves. The psbA mRNA half-life was increased more than twofold in mature leaves compared with young leaves, whereas rbcL mRNA decayed with a similar relative half-life at both leaf developmental stages. The direct in vivo measurements demonstrated that differential mRNA stability in higher plant plastids can account for differences in mRNA accumulation during leaf development. The role of polysome association in mRNA decay was also investigated. Using organelle-specific translation inhibitors that force mRNAs into a polysome-bound state or deplete mRNAs of ribosomes, we measured mRNA decay in vivo in either state. The results showed that rbcL and psbA mRNAs are less stable when bound to polysomes relative to the polysome-depleted mRNAs and that their stabilities are differentially affected by binding to polysomes. The results suggested that ribosome binding and/or translation of the psbA and rbcL mRNAs may function to modulate the rate of their decay in chloroplasts.

Localization of Abutilon Mosaic Virus (AbMV) DNA within leaf tissue by in situ hybridization

Abutilon mosaic virus (AbMV) is a whitefly-transmitted geminivirus with a bipartite genome. Using in situ hybridization AbMV DNA was detected exclusively in the phloem of infected Abutilon sellovianum leaves and intracellularly predominant in the nuclei. No AbMV DNA was found in cells from palisade and spongy parenchyma, the tissues which show the predominant cytopathological effects. A hypothesis is discussed to account for the finding that, while AbMV accumulates in the phloem, symptoms are observed in other tissues. Shoot tips were analyzed by in situ hybridization to determine the earliest stage of leaf development in which AbMV is detectable. We found the first hybridization signals in the sixth to seventh leaf of the shoot tip, whereas we could not detect any viral DNA in younger leaves and meristems. These results are discussed with reference to the relation of AbMV multiplication to the cell cycle.

Growth and Development of the Lactuca sativa Shoot as Affected by NaCl Stress: Consideration of Leaf Developmental Stages

The effect of salinization on development of the whole shoot and individual leaves of Lactuca sativa L. cv Black-seeded Simpson was studied nondestructively. Salinization by 80 mol m-3 NaCl (from the 10 mol m-3 control concentration) slowed shoot development. The lengthening of the plastochron because of salinization was evident in rates of leaf expansion, frequency of leaf emergence, and growth rate of the whole shoot. The plastochron effect on shoot development was sufficient to account for a 33% reduction in biomass of the shoot, equaling the entire growth inhibition measured during the first week following salinization. A second effect, reduction in maximum leaf size, could be measured after 2 more wk of plant growth. A 50% reduction in fresh weight of fully mature leaves of salinized plants was evident in leaves already beyond the most rapid phase of expansion at the time of salinization. Curtailment of the slow phase of leaf expansion seems, therefore, to reduce maximum leaf size. This cultivar lends itself to nondestructive growth study because of its rapid growth, high rate of leaf emergence, the open access to its leaves, and the absence of a significant contribution by the stem to shoot biomass. Mathematical reconstruction of the shoot allows comparison with results from destructive studies measuring growth of the bulked shoot.

Daily Tall Fescue Leaf Appearance Rate in Relation to Environmental Factors

Methods for detecting and mathematically regressing daily tall fescue (Festuca arundinacea Schreb.) leaf appearance on environmental variables are presented. Morphological stages of leaf development were quantified and the rate of leaf appearance was linearly regressed on environmental variables. The following model was developed to predict daily tall fescue leaf appearance and was successfully tested on unrelated data: Daily leaf appearance rate = 0.016 – (2.48 × 10-4 × solar radiation) + (0.015 × precipitation 2-day lag) + (0.117 × soil moisture 3-day lag) + (8.79 × 1 0-6 × maximum air temperature × solar radiation) - (3.61 × 10-' × maximum air temperature × age) + (0.00307 × minimum air temperature × precipitation) – (4.39 × 10-4 × precipitation × age), (R2 = 0.78). Growers of tall fescue and researchers will benefit in the identification of environmental characteristics and cultural practices that significantly influence leaf appearance rate.

Distribution of photosynthetically fixed 14CO 2 into essential oil in relation to primary metabolites in developing peppermint ( Mentha piperita) leaves

Changes in essential oil content, CO 2 exchange rate and distribution of photosynthetically fixed 14CO 2 into essential oil, amino acids, organic acids and sugars were determined in developing peppermint leaves. The incorporation of 14CO 2 into sugars was maximal followed by organic acids, amino acids and essential oil at all stages of leaf development. The incorporation into sugars and amino acids declined as the leaf matured whereas that in essential oil and organic acids increased with leaf expansion and then decreased.

Identification of cytokinins and the changes in their endogenous levels in developingCitrus sinensisleaves

SummaryEndogenous cytokinins at different stages of leaf development were determined in Citrus sinensis using Sephadex LH-20 column chromatography, HPLC, GC-MS and bioassays. Cytokinin active fractions corresponding to ribosyl zeatin, isopentenyl adenine and cyto- kinin ribotides were present in all developmental stages studied and also to the glycosides of ribosyl zeatin and zeatin in mature leaves. The identity of ribosyl zeatin was confirmed by the use of HPLC and GC-MS.

Isozyme Analysis of Yamamomo(Myrica rubra Sieb.et Zucc.)Cultivars.

Glutamate oxaloacetate aminotransferase (GOT) and peroxidase (POD) isozymes of yamamomo (Myrica rubra SIEB. et ZUCC.) cultivars were analyzed by native polyacrylamide gel electrophoresis (PAGE). A Leaf bud was sampled for enzyme extraction due to the strongest actlvity of the enzyme at this stage of leaf development. Since the elect.rophoretic patterns of two zones of GOT isozymes and one of POD isozymes varied among the cultivars, it was considered that the combination of the zones of these isozymes would enable to identify cultlvars with different names as synonyms or, on the contrary, cultivars with similar names as different ones. Two cultivars, considered to be of Chinese origin, could apparently be distinguished from the other Japanese cultivars by such isozyme analysis.

Formation of functionally active chloroplasts is determined at a limited stage of leaf development in virescent mutants of rice

AbstractThe ability to form functionally active chloroplasts is determined at a certain early stage of leaf development in three non‐allelic temperature‐sensitive virescent mutants of rice. Temperature‐shift analysis, together with anatomical observations, indicates that the intrinsic developmental signals of the virescent genes are expressed at the stage immediately following the formation of basic leaf structure, but just before the onset of leaf elongation. These signals control the expression of chloroplast‐encoded genes but do not affect the subsequent morphological development of the leaf or the photo‐regulation of the expression of nuclear genes encoding chloroplast proteins.

The effect of leaf source and developmental stage on shoot organogenic potential of sweetgum (Liquidambar styraciflua L.) leaf explants

Leaf explants harvested from shoot proliferating cultures and intact plants of Liquidambar styraciflua ‘Variegata’ were placed on solidified Woody Plant medium supplemented with 0.1 mgl-1 (0.5 μM) naphthaleneacetic acid and 2.5 mgl-1 (11.1 μM) benzyladenine to initiate shoot meristems directly. Leaves from intact plants produced over 4 times more adventitious shoots than leaves from in vitro shoots and had a greater tendency to form shoots on the lamina. The relative developmental age of leaf tissue used dramatically influenced the shoot organogenic response observed for leaf explants from intact plants of L. styraciflua ‘Variegata’ and ‘Moraine’.-Leaves that were either 20% or 50% of full size and still actively expanding were superior to other developmental stages for shoot organogenesis. As developmental leaf age increased throughout the period of leaf expansion, the number of shoots forming on the petiole stub remained constant, whereas shoot formation on the lamina increased 8 fold. Shoots derived from ‘Variegata’ leaves rooted well and grew normally as plants. Differences in rooting ability and plant size could be detected between groups that had been separated according to explant source (in vitro vs. intact plant) and the location of shoot formation (petiole vs. lamina).

Efficacy of five different formulations of clopyralid on Cirsium arvense (L.) Scop, and Polygonum convolvulus L

Summary:Experiments were conducted in a controlled environment growth room to compare the phytotoxicity of five formulations of clopyralid and to determine the effect of post‐treatment simulated rainfall applications on the efficacy of these formulations. Clopyralid, formulated as the acid, monoethanolamine salt, potassium salt, 2‐ethylhexyl ester or 1‐decyl ester was applied to Cirsium arvense or Polygonum convolvulus at the 8–10 and 4–6 leaf stage of development, respectively.Based on the shoot and root dry weight data from both species, the 2‐ethylhexyl ester was consistently less phytotoxic than the other four formulations. With respect to Cirsium arvense shoot and root dry weight, there was no difference in efficacy between the acid, monoethanolamine salt, potassium salt and 1‐decyl ester. Root dry weight changes of Polygonum convolvulus did not correlate well with an increase in dose of the five formulations. Maximum increase in stem diameter of Polygonum convolvulus occurred after application of 100 g a.e. ha−1 of the acid, monoethanolamine salt, potassium salt and 1‐decyl ester whereas with the 2‐ethylhexyl ester, the maximum increase occurred after application of 200 g a.e. ha−1. Simulated rainfall was applied 3, 6, 9 or 12 h after application of 200 g a.e. ha−1 of the five clopyralid formulations to both species. Rainfall reduced the efficacy of clopyralid, regardless of the formulation or species. The 2‐ethylhexyl ester was less efficacious than the other four formulations, irrespective of the timing of simulated rainfall.

The influence of ancymidol on morphology, anatomy, and chlorophyll levels in developing and mature Helianthus annuus leaves

Ancymidol foliar spray at 132 mg·liter−1 a.i. modified leaf anatomy of developing Helianthus annuus L. ‘Mammoth Russian’ leaves, but not of mature leaves. Ancymidol was effective in retarding plant growth when applied at the young seedling or at a more mature stage of growth. Ancymidol increased leaf weight per unit area and chlorophyll content on an area and unit weight basis, regardless of stage of leaf development. Total chlorophyll per leaf was also increased in mature leaves. Thus, darker green foliage due to increased chlorophyll content and modified leaf anatomy responses were determined to be independent effects.

Preanthesis Tiller Mortality in Spring Wheat

A primary determinant of yield in wheat (Triticum aestivum L.) is the number of spike‐bearing tillers per unit area. Many tillers that emerge do not survive to produce spikes. This study was conducted to determine the point in development when tillers begin to senesce and to examine how premature senescence is affected by water deficits and plant population. Cultivars Edwall and Waverly were planted in a 2‐yr field study at two plant densities (168 and 84 kg ha−1 in 15‐ and 30‐cm rows, respectively) and with both irrigated and nonirrigated treatments. The Haun stage of leaf development was monitored weekly on five plants per plot. Tiller mortality was monitored from tiller emergence until maturity. For tillers destined to die prematurely, a reduced rate of leaf emergence and development was evident immediately after tiller emergence. The majority of tillers senesceduring main stem extension, while almost no tillers were lost during grain filling. The maximum Haun stage reached by senescing tillers was normally ≤3 for all tillers excepthe coleoptile (TO) tiller. For this tiller, the maximum Haun stage was ≤4. Premature tiller senescence occurred in both irrigated and nonirrigated plots and was greatest at the higher plant density. Water deficits increased the number of tillers that died but did not affect the stage at which senescence occurred. Tillers that emerged late during plant development were most likely to senesce prematurely.

Rootworm and Mechanical Damage Effects on Root Morphology and Water Relations in Maize

There is little information in the literature concerning the effect of corn rootworm larval feeding on the physiology of maize (Zea mays L.). This study was conducted to determine if root damage caused by western corn rootworms (Diabrotica virgifera virgifera LeConte) affects relative water content, leaf water potential, or stomatal conductance in leaves of the host plants. The effect of mechanical root‐cutting treatments was also evaluated. The experiment was conducted under controlled‐environment conditions in a greenhouse. Plants were damaged at the V9 stage of leaf development by prior infestation with 50 or 150 larvae per plant or by cutting 25 or 75% of the root system from the plant. Root systems and plant water relations were evaluated at this stage of development and again at tassel. Larval root damage was confined to the axes of the fourth and fifth nodes of roots. There were no differences in relative water content, leaf water potential, or stomatal conductance between infested plants or controls at V9; at tassel, however, leaf water potential was significantly higher and stomatal conductance was significantly less in infested plants (P < 0.05). Mechanical cutting of roots caused significant differences (P < 0.05) in relative water content and stomatal conductance at both sampling dates. These results indicate that mechanical root damage reduced the ability of root systems to provide adequate water to the shoots to a much greater extent than did corn‐rootworm damage.

Seasonal changes of furanocoumarin concentrations in leaves ofHeracleum lanatum

Concentrations of three dermatitis-inducing furanocoumarins- xanthotoxin, bergapten and psoralen-were measured in whole leaves ofHeracleum lanatum and in extracts of the leaf surface over an entire vegetative season. The concentrations of surface furanocoumarins, localized by extraction involving brief dipping in almost-boiling water followed by HPLC quantitative analysis, increased until the middle of May and decreased until maturity. The concentration on autumn leaves (new growth) was 20-100 times as high as the ones in May, or those of similar size in April. Furanocoumarin concentrations in the whole leaf at different stages of leaf development varied, being the highest April 25, then decreasing sharply with rapid leaf enlargement. Again, in the small autumn leaves the coumarin concentration was two to three times that in April. Seasonal changes in surface furanocoumarins may be important in that these compounds are postulated to form the first defense barrier of the plant.

Abscisic acid and gibberellins in the fruitlets and leaves of ‘Valencia’ orange in relation to fruit growth and retention

Fruit growth and abscission, as well as gibberellins (GA, mainly 1 and 3) and free and bound abscisic acid (ABA) in the fruitlets and subtending leaves, were monitored in ‘Valencia’ orange ( Citrus sinensis) from full bloom (FB), with the aim of identifying the physiological factors influencing fruit growth. Particularly from 30 days after FB, the mass of fruitlets adjacent to young leaves (“leafy” fruitlets) were greater than fruitlets adjacent to mature leaves (“leafless” fruitlets). In addition, leafy fruitlets showed considerably greater tree retention after 10 weeks (12.7%) than leafless fruitlets (1.2%). There was little difference in ABA and GA concentrations between the leafy and leafless fruitlets, and concentrations were fairly consistent throughout the 10-week analysis period. However, the masses of ABA and GA per fruit increased during growth. Leaf ABA and GA concentrations remained fairly constant except during the very early stages of leaf development, and the mature leaves contained greater concentrations than the immature leaves. These results are discussed in relation to the role of plant growth substances in citrus fruit growth.

Leaf morphology and water status changes in Triticum durum under water stress

Water relations, leaf morphology and the chemical composition of cell walls in irrigated and unirrigated plants of three durum wheat eultivars were measured at two growth stages (booting and flowering). Plant response to water stress differed at the two stages: cell wall elasticity increased at booting and osmotic potential values decreased at flowering; this may be due to the changes in stress history, leaf development and plant growth stage between the two harvests. Leaf tissue characteristics were modified by water stress only at flowering: accumulation of fibrous constituents and hemicellulose in the cell walls, reduction of acid detergent fiber (ADF) per unit of leaf area, increase in specific leaf weight (SLW), decrease in turgid weight/dry weight ratio (TW/DW) and alteration in mesophyll cell morphology (cell area / ceil perimeter ratio) were observed.Generally, cv. Valforte (the less drought‐resistant cultivar) had the greatest mesophyll cell area and perimeter and it had greater values of neutral detergent fiber (NDF) at the booting stage than cv. Appulo. Reactivity to water stress differed in the eultivars: Valforte showed the greatest increase in hemicellulose content and decrease in cell dimensions under drought at flowering.No significant relationships between osmotic potential and mesophyll cell characters were observed; there were no correlations among cell wall elasticity, cell morphology and the chemical components of leaf tissue. The total fiber content and the hemicellulose per unit of leaf area were correlated with the TW/DW ratio at flowering. This parameter decreased more in plants subjected to water stress owing to accumulation of hemicellulose. Correlations between leaf structural constituents and $$ suggest that the absorptive capacity of the cell wall may significally affect the osmotic volume of the cell.

Ranking introduced into phenological recording

Generally, phenological recording is based on the recognition of separate phases of development in the organism of interest. In the present study samples were ranked with respect to the stage of bud or leaf development reached at the time of sampling. In April 1982 budding and leaf development of all species of trees and shrubs were recorded over 2 km2 of the northeastern slope of Navlingeasen, a horst in southernmost Sweden. During 3 days, of which the first two were consecutive, the author walked a stretch of 12 km, divided into 107 sections. In each of these the first living twig at about 1.5 m above ground was sampled for each species. At the end of the day all twigs from the same species were ranked by two persons independently. The ranks were normalized, and a mean calculated for each section. To reduce the impact of natural variation within a species, and also the influence of microclimate where species cluster, the ranks of the sections were smoothed by weighted moving averages. Using three localities which were investigated twice as fixed points, the ranking lists of separate days were integrated into a single system. A time lag of 4 or 5 days in the onset of spring was established between different localities.

Leaf domatia and mites on Australasian plants: ecological and evolutionary implications

Leaf domatia, specialized chambers in the vein axils on the underside of leaves of many plant species, have remained an enigma for over a century. In this study we show a strong association between foliar domatia and mites in 37 plant species in Australasia. Overall, mites accounted for 91% of the arthropods observed in domatia. Across all species, a median of 51% of domatia were occupied and 71% of leaves showed mite evidence in domatia. The level of mite association did not depend on domatia type (pit, pouch, pocket, or tuft) or provenance (Papua New Guinea, Queensland, Victoria, or New Zealand). Mite association with domatia commonly varied between plant species, between individuals within species, and between shoots within individuals. The leaf developmental stage probably explains much of the variation in association for many of these species. The presence of a variety of life history stages of mites within domatia indicates that these structures act as shelters for development and reproduction. Furthermore, in 12 of 13 plant species examined, domatia concentrate mites in particular locations on the leaf. Mite taxa that we classify as largely predaceous (e.g. phytoseiids, stigmaeids and tydeids) or fungivorous (e.g. acarids and oribatids) were most common in domatia and dominated the association in 21 of 24 plant species in which the relative abundance of herbivorous, fungivorous and predaceous groups was quantified. We evaluate hypotheses that explain the role of leaf domatia, including non-functional hypotheses (e.g. architectural constraints), physiological function (e.g. gas exchange and water uptake), bacterial symbiosis and antagonistic and mutualistic associations with mites. Our quantitative results confirm anecdotal accounts of mite association with leaf domatia and are most consistent with Lundstroem's century-old hypothesis of plant-mite mutualism in which leaf domatia billet predaceous and fungivorous mites that prey on plant enemies. Leaf domatia are widespread among woody angiosperms and abundant in many temperate and tropical regions of Australasia. Mites, an ancient group of arthropods whose diversity and abundance parallels that of insects, are likely to be important selective agents on terrestrial plants. Our results (1) indicate that mite-domatia association represents a relationship of comparable scope to plant-ant associations mediated by specialized plant structures such as extrafloral nectaries, food bodies and specialized domatia; (2) suggest that sociality is not a necessary prerequisite for widespread and diverse mutualisms between arthropods and plants; and, (3) extend the diversity of organisms that produce specialized mite ‘houses’ from lizards, and wasps and bees to woody angiosperms.

Phyllotaxy and Stage of Leaf and Fruit Development Influence Initiation and Direction of Carbohydrate Export from Sour Cherry Leaves

Abstract The influence of phyllotaxy and stage of leaf and fruit development on the initiation and direction of carbohydrate (CH2O) export from sour cherry (Prunus cerasus L.) leaves was investigated during two different seasons. One-year-old ‘Montmorency’ sour cherry trees on ‘Mahaleb’ rootstock were pruned to a single shoot, the seventh and 10th leaf (from the base) were pulsed with 14CO2, and labeled carbon products were located after 24 hr using autoradiography. In 1983, gross export (EG) from the seventh and 10th leaf was initiated when the area of the seventh leaf reached 8.5 cm2 (27% expansion) and when that of the 10th leaf reached 14 to 21 cm2 (48% to 72% expansion), respectively. EG was generally initiated later in 1985 than in 1983, for the seventh leaf later than 26 cm2 (47% expansion) and for the 10th leaf at 36 cm2 (78% expansion). Leaf size was greater at full expansion in 1985 than in 1983. On defoliated shoots, the 10th leaf (54 ± 16 cm2 full expansion) started export between 24 and 28 cm2 (44% to 52% expansion), whereas control leaves on nondefoliated shoots started export at 36 cm2 (78% expansion). We suggest that, after a leaf has developed the potential for phloem loading, the onset of CH2O export is a function of the CH2O availability in the plant at the time of leaf expansion. Translocation paths followed closely the orthostichy of the exporting leaf. Fruit effects on the direction of translocation were studied in 2-year-old trees. During stages I and III of fruit development, leaves closest to the base showed basipetal translocation only. All leaves during stage II and leaves distal to the midpoint of the shoot during stages I and III showed bidirectional translocation to the shoot apex and the fruits.

CONTROL OF WILD MUSTARD IN CANOLA WITH POSTEMERGENCE HERBICIDES

Field studies were conducted in 1986 and 1987 to determine the effectiveness of DPX-A7881 [methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazin-2-yl) = carbamoyl-sulphanoyl]benzoate] and imazamethabenz for the selective removal of wild mustard Sinapis arvensis L. (Brassica kaber [DC] Wheeler var. pinnatifida [Stokes] Wheeler) from canola (Brassica napus L.). Both DPX-A7881 and imazamethabenz controlled wild mustard when applied at the proper dosage and stage of growth. Susceptibility of wild mustard to either herbicide declined when the herbicide treatment was delayed beyond the six-leaf stage. DPX-A7881 applied postemergence at 10–15 g a.i. ha−1 to wild mustard seedlings in the cotyledon leaf stage of development did not reduce crop yields and significantly reduced the level of 4-hydroxy-benzyl glucosinolate from wild mustard found in canola meal. Canola cultivar Global exhibited greater tolerance to post-emergence applications of DPX-A7881 than to imazamethabenz. The total concentration of canola glucosinolates was found to increase in seed samples taken from plants injured by postemergence applications of imazamethabenz.Key words: Canola, herbicides, wild mustard, seed yield, glucosinolates