scholarly journals Developmental studies on Euphorbia esula: seasonal variation in the apices of long roots

1976 ◽  
Vol 54 (7) ◽  
pp. 605-610 ◽  
Author(s):  
M. V. S. Raju ◽  
T. A. Steeves ◽  
J. Maze
Keyword(s):  
Seasonal Variation ◽  
Growing Season ◽  
Large Percentage ◽  
Euphorbia Esula ◽  
Developmental Studies ◽  
Quiescent Centre ◽  
Root Apices

Long-root apices of Euphorbia esula L. were supplied with [3H]thymidine in the field on 11 occasions during the growing season. Autoradiographs of the root apices showed that the characteristic quiescent centre of long roots was absent in a large percentage of the roots in the early part of the growing season. It is suggested that the cells of the quiescent centre play an important role in the seasonal reactivation of the perennial roots of this species.

DEVELOPMENTAL STUDIES ON EUPHORBIA ESULA L.: APICES OF LONG AND SHORT ROOTS

1964 ◽  
Vol 42 (12) ◽  
pp. 1615-1628 ◽  
Author(s):  
M. V. S. Raju ◽  
T. A. Steeves ◽  
J. M. Naylor
Keyword(s):  
Cell Division ◽  
Root Apex ◽  
Root Cap ◽  
Field Conditions ◽  
Euphorbia Esula ◽  
Quiescent Center ◽  
Developmental Studies ◽  
Short Root ◽  
Root Apices ◽  
Root Axis

In both indeterminate long roots and determinate short roots of Euphorbia esula L., the promeristem usually consists of three meristematic layers. One of these represents the stelar pole, the second is continuous with the cortex, and the most distal appears to initiate the root cap – epidermis complex. Variations in this pattern are noted. Autoradiographs of apices of roots supplied with thymidine-H3 under field conditions demonstrate the existence of a region of low nuclear incorporation during a 24 or 48 hour period at the summit of the root axis in long roots. This region corresponds to the quiescent center described by previous authors. Short root apices consistently lack such a region. The pattern of nuclear incorporation of thymidine-H3 suggests that cell division is infrequent or absent in the center of the apex of long roots but not of short roots. Quiescence is thus a phenomenon which is superimposed upon the organization of the root apex in this species, and its presence or absence seems to be related to the developmental potentiality of the root. In many long roots the size of this quiescent region exceeds that of the region which may reasonably be designated the promeristem.

Primary vascular patterns in root meristems of Pontederia cordata and their relevance to studies of root development

1980 ◽  
Vol 58 (12) ◽  
pp. 1351-1369 ◽  
Author(s):  
W. A. Charlton
Keyword(s):  
Apical Meristem ◽  
Vascular System ◽  
Root Apex ◽  
Root Apical Meristem ◽  
Vascular Pattern ◽  
Quiescent Centre ◽  
Vascular Differentiation ◽  
Pontederia Cordata ◽  
Distribution Of Components ◽  
Root Apices

There are several files of metaxylem cells in root apices of Pontederia cordata L., each considered to consist of a series of prospective vessels with their ends in contact. Two longitudinally adjacent vessels may be in the same file of cells produced by the root apex or in adjacent files. As the root grows, successive prospective vessels are added to the apical ends of most of the files but not all files are continued. Addition of prospective vessels appears to take place within the "quiescent centre" of the root apical meristem. Where files are not continued there is no immediate readjustment of remaining files. The longitudinal and transverse distribution of components of the vascular system (including protophloem and protoxylem) is discussed in relation to the means by which the pattern of development may be controlled. Rates of production of vessels and the final lengths of the vessels are estimated. The observations and deductions are discussed in relation to other studies of root growth, vascular differentiation, and vascular pattern formation and maintenance.

DEVELOPMENTAL STUDIES ON EUPHORBIA ESULA L.: MORPHOLOGY OF THE ROOT SYSTEM

1963 ◽  
Vol 41 (5) ◽  
pp. 579-589 ◽  
Author(s):  
M. V. S. Raju ◽  
T. A. Steeves ◽  
R. T. Coupland
Keyword(s):  
Root System ◽  
Lateral Roots ◽  
Primary Root ◽  
Cambial Activity ◽  
Euphorbia Esula ◽  
Developmental Studies ◽  
Limited Growth ◽  
Mode Of Reproduction ◽  
Shoot Buds ◽  
Adverse Conditions

The significance of Euphorbia esula L. as a weed is related to its capacity to persist under adverse conditions and to its mode of reproduction. In both these properties, the root system plays an important role. The root system is initially established by seedlings. The seedling has a vigorous primary root with extensive longitudinal growth and considerable cambial activity. Such a root has been designated a "long" root. By contrast, the first lateral roots produced on the primary root have limited growth and no cambial activity. These roots have been termed "short" roots. Thus, the seedling exhibits a "heterorhizic" pattern. Lateral long roots also arise on the primary root of seedlings but their origin is delayed until cambial activity has begun. Such lateral long roots arise much earlier on seedlings growing in denuded areas than on those growing in areas covered by dense vegetation. The mature root system is described in terms of horizontal and vertical long roots, which make up the conspicuous framework of the system, and of the short roots which they produce. Long roots produce shoot-buds and the origin of these structures is delayed until cambial activity has started. Short roots do not give rise to shoot-buds. Cambial activity in long roots appears to be connected with bud production and its absence in short roots probably underlies their inability to produce buds.L'importance de Euphorbia esula L. comme mauvaise herbe est connexé a son capacité de persister dans les situations hostiles et à sa methode de reproduction. Dans ces deux caractéristiques, le système des racines a une signification profunde. Initialement le système des racines s'établit dans le semis. Le semis a une racine primaire très forte avec beaucoup de croissance longitudinale et avec une activité considérable du cambium. Une racine de cette espèce s'appelle une "longue" racine (long root). Par contre, les premières racines latérales que poussent sur la racine primaire ont croissance limité et aucun activité du cambium. Ces racines s'appellent les "courtes" racines (short roots). De cette façon, le semis montre un dessin "heterorhizique" (heterorhizic). Les longues racines latérales ont aussi leur origine sur la racine primaire du semis, mais l'origine est retardé jusqu'au commencement de l'activité du cambium. Les racines de cette espèce apparaissent beaucoup plus tôt sur les semis qui sont situés en terre sans autre végétation, que sur ceux qui sont situés au milieu des autres plantes. Le système adulte des racines se décrit sous forme des longues racines de l'espèce horizontale et verticale, lesquelles constituent la charpente bien visible du système, et des courtes racines que sont produites par les longues racines. Les longues racines produisent les bourgeons, mais l'origine des bourgeons est retardé jusqu'au commencement de l'activité du cambium dans les racines. Les courtes racines ne produisent pas les bourgeons. Il paraît que l'activité du cambium dans les longues racines soit corrélative avec l'initiation des bourgeons et l'absence du cambium dans les courtes racines explique probablement leur incapacité à produire les bourgeons.

Weed Survey System used in Saskatchewan for Cereal and Oilseed Crops

Weed Science ◽  
1985 ◽  
Vol 33 (1) ◽  
pp. 34-43 ◽  
Author(s):  
A. Gordon Thomas
Keyword(s):  
Growing Season ◽  
Agricultural Extension ◽  
Sampling Procedure ◽  
Distribution Maps ◽  
Agricultural Extension Service ◽  
Polygonum Convolvulus ◽  
Green Foxtail ◽  
Survey System ◽  
Weed Survey

A weed survey system methodology was developed and used annually for 4 yr in the province of Saskatchewan. Based on a stratified random sampling procedure, fields were selected in wheat (Triticum aestivumL.), barley (Hordeum vulgareL.), oat (Avena sativaL.), rye (Secale cerealeL.), rape (Brassica napusL.,Brassica campestrisL.), and flax (Linum usitatissimumL.) crops. The boundaries of the 43 agricultural extension districts in the province formed the strata. The provincial agricultural extension service provided staff to conduct the survey. Computer processing of the data enabled reports, containing summary tables and distribution maps, to be distributed to extension, research, and industry personnel within 3 months after completion of the field survey. The field surveys were conducted late in the growing season before harvest commenced; hence, the weed populations consisted of species that had been present during the early part of the growing season and may have contributed to yield losses. During the 4 yr of the survey, weeds were counted in 4423 fields. Of the 164 species recorded, 97 species occurred in more than three fields. Only 29 species were encountered frequently in the fields. Green foxtail [Setaria viridis(L.) Beauv. # SETVI), wild buckwheat (Polygonum convolvulusL. # POLCO), and wild oat (Avena fatuaL. # AVEFA) were the top three species based on a ranking system using a measure called relative abundance.

Influence of Oxadiazon on Peanuts and Weeds1

1977 ◽  
Vol 4 (1) ◽  
pp. 37-41 ◽  
Author(s):  
Gale A. Buchanan ◽  
Paul A. Backman ◽  
R. Rodriguez-Kabana
Keyword(s):  
Weed Control ◽  
Arachis Hypogaea ◽  
Growing Season ◽  
Mixed Population ◽  
Annual Grass ◽  
Predominant Species ◽  
Time Treatment ◽  
Arachis Hypogaea L ◽  
Substantial Control

Abstract Oxadiazon [2-tert-butyl-4-(2, 4-dichloro-5-isopropoxyphenyl)- Δ2-1,3,4-oxadiazolin-5-one] was applied alone as a preemergence treatment and in combination with dinoseb (2-sec-butyl-4,6-dinitrophenol) as a cracking-time treatment to peanuts (Arachis hypogaea L.). During the years 1970 to 1972 the experimental area was heavily infested with a mixed population of annual grass and broadleaf weeds. During the years 1973 to 1975, the predominant species present were sicklepod (Cassia obtusifolia L.) and Florida beggarweed [Desmodium tortuosum (Sw.) D.C.]. Grass control was acceptable with 3.36 kg/ha of oxadiazon in 2 of the 3 years when benefin (N-butyl-N-ethyl-∝, ∝, ∝ -trifluoro-2, 6-dinitro-p-toluidine) was not included. Commercially acceptable control of Florida beggarweed and sicklepod occurred with application of 3.36 kg/ha of oxadiazon. Substantial control was obtained with an application of 1.68 kg/ha. Generally, the addition of 1.68 kg/ha dinoseb to oxadiazon resulted in slightly improved weed control, particularly at lower rates of oxadiazon. Oxadiazon at rates of 6.7 kg/ha or more was phytotoxic to peanuts during the early part of the growing season. This phytotoxicity generally did not result in lower peanut yields. However, treated plants were more compact.

Analysis of Observed and DNDC Modeled Soil Respiration of Winter Wheat in Guanzhong Plain

2014 ◽  
Vol 1073-1076 ◽  
pp. 1216-1221
Author(s):  
Xiao Long Zhang ◽  
Xue Yang ◽  
Kai Di Tian ◽  
Bing Shen ◽  
Quan Quan
Keyword(s):  
Seasonal Variation ◽  
Soil Respiration ◽  
Winter Wheat ◽  
Significant Variation ◽  
Root Respiration ◽  
Growing Season ◽  
Dndc Model ◽  
Experimental Station ◽  
Soil Heterotrophic Respiration ◽  
Planting Season

The application of the DeNitrification-DeComposition (DNDC) model in soil respiration of winter wheat at the Ecological Experimental Station of Fuping County, China is researched for the year 2013-2014. The applied results indicate that DNDC is available to research soil respiration in cropland agroecosystems of Guanzhong Plain, China. Also the cumulative and seasonal variation emissions of soil respiration and components (root respiration, soil heterotrophic respiration) are estimated. Based on the simulated results, it can be seen that a significant variation appears in winter wheat growing season, where a downward trend starts from planting season to wintering season, and a steady low level at about 8.3 kg C·hm-2·d-1 keeps until the overwintering, then a significant upward to harvest, where the top point is almost 101.84 kg C·hm-2·d-1, with the total amount is 8342.35 kg C·hm-2. The seasonal amount of root respiration is 5345.47 kg C·hm-2, occupies 61.1% of soil respiration emissions.

PHOTOPERIODIC RESPONSE OF BEGONIA × HIEMALIS CV. RIEGER

1974 ◽  
Vol 54 (2) ◽  
pp. 277-280 ◽  
Author(s):  
J. M. MOLNAR
Keyword(s):  
Day Treatment ◽  
Growing Season ◽  
Photoperiodic Response ◽  
Full Bloom ◽  
Short Day

Two consecutive experiments demonstrated that Rieger elatior begonia cultivars Schwabenland Red and Aphrodite Cherry Red flowered earlier and most abundantly when they were grown under long days (16 h) at the early part of their growing season, followed by 3 wk of short day conditions (10 h). The plants were in full bloom within 6 wk from the time the short-day treatment began.

Fecundity of male rabbits as determined by “dummy matings”

1938 ◽  
Vol 28 (1) ◽  
pp. 122-134 ◽  
Author(s):  
C. Macirone ◽  
Arthur Walton
Keyword(s):  
Seasonal Variation ◽  
Individual Variation ◽  
Sperm Production ◽  
Sexual Stimulation ◽  
Sex Drive ◽  
Short Period ◽  
The Relationship ◽  
Average Fertility ◽  
Artificial Vagina

A method of obtaining samples of semen from rabbit males by means of a dummy and artificial vagina is described. The volume of the semen, and the number of spermatozoa per cm. (density) and the total number of spermatozoa in the sample have been measured. The data obtained from these measurements have been analysed under the following headings:1. Relation between total volume and total number of spermatozoa. With an increase in the total volume of the ejaculate there is an increase in the total number of spermatozoa, but the relationship is not linear. The density of spermatozoa varies considerably.2. Seasonal variation. Seasonal variation in sperm production is not marked in these data. There is slight tendency for the numbers to be highest in the early part of the year and lowest in August and September when the animal is moulting.3. Individual variation. In each individual, variation is considerable. Differences between individuals are not marked, but as most of the animals were of low average fertility, it is probable that this result is not typical of male rabbits in general.4. Effect of successive matings with in a short period. In successive matings the number of spermatozoa diminishes rapidly. As the density is not much affected, the diminution is due to reduction in the volume of the ejaculate.5. Relation between the number of spermatozoa in the ejaculate and the number in the various sections of the spermatic tract. After a series of samples had been obtained, some males were killed and an estimate made of the number of spermatozoa present in various parts of the tract. From the results it is concluded that on ejaculation the vas deferens is practically emptied and that some sperm in the ejaculate come from the cauda epididymis.6. Observations on sexual behaviour. The sexual pattern of the male rabbit is described and the relation between sexual stimulation and sex drive is discussed.

scholarly journals Rootstock Effects on the Flowering of `Delicious' Apple. I. Bud Development

1995 ◽  
Vol 120 (6) ◽  
pp. 1010-1017 ◽  
Author(s):  
Peter M Hirst ◽  
David C Ferree
Keyword(s):  
Floral Development ◽  
Dry Weight ◽  
Growing Season ◽  
Flower Formation ◽  
Full Bloom ◽  
Floral Buds ◽  
One Year ◽  
Floral Bud ◽  
Leaf Dry Weight

Floral development was studied in buds of `Starkspur Supreme Delicious' apple trees growing on B.9, M.26 EMLA, M.7 EMLA, P.18, and seedling rootstocks. In each of 3 years, buds were sampled from the previous years growth at intervals throughout the growing season and dissected to determine whether the apex was domed, indicating the start of floral development. Number of bud scales and true leaves increased during the early part of the growing season, but remained fairly constant beyond 70 days after full bloom. The type of rootstock did not affect the number of bud scales or transition leaves, and effects on true leaf numbers were small and inconsistent. Final bract number per floral bud was similarly unaffected by rootstock. The proportion of buds in which flowers were formed was influenced by rootstock in only one year of the study, which was characterized by high temperatures and low rainfall over the period of flower formation. Bracts were observed only in floral buds, and became visible after doming of bud apices had occurred. Flowers were formed during the first 20 days in August, regardless of rootstock or year. The appendage number of vegetative buds was constant from 70 days after full bloom until the end of the growing season, but the number of appendages in floral buds increased due to the continued production of bracts. The critical bud appendage number for `Starkspur Supreme Delicious' before flower formation was 20, and was stable among rootstocks and years. Buds with diameters above 3.1 mm were generally floral, but on this basis only 65% of buds could be correctly classified. Spur leaf number, spur leaf area, and spur leaf dry weight were not good predictors of floral formation within the spur bud.

scholarly journals Genotype and Seasonal Variation Affect Yield and Oil Quality of Safflower (Carthamus tinctorius L.) under Mediterranean Conditions

Agronomy ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 122
Author(s):  
Lara Abou Chehade ◽  
Luciana G. Angelini ◽  
Silvia Tavarini
Keyword(s):  
Fatty Acid Composition ◽  
Oleic Acid ◽  
Seasonal Variation ◽  
Fatty Acid ◽  
Linoleic Acid ◽  
Plant Height ◽  
Seed Yield ◽  
Oil Quality ◽  
Growing Season ◽  
Mediterranean Conditions

The adoption of climate-resilient and resource-use efficient crop species and varieties is a key adaptation action for farmers in the face of climate change. Safflower, an emerging oilseed crop, has been recognized for its high oil quality and its favorable agronomic traits such as drought and cold tolerance, making it particularly suitable to Mediterranean conditions. A 2-year field study was carried out to evaluate the effects of the genotype and growing season on the crop phenology, seed and oil production, macronutrient accumulation and partitioning, and fatty acid composition of spring-sown safflower grown under rainfed conditions. The experiment was conducted during the 2012 and 2013 growing seasons on an alluvial deep loam soil (Typic Xerofluvent) at the Centre for Agri-environmental Research “E. Avanzi” of the University of Pisa (Pisa, Central Italy). Higher seed yield and yield components (plant density, plant height, branching, number of capitula per plant and seeds per capitulum) were found in almost all genotypes when the seeds were sown in mid-March 2012 compared to in late April 2013. More favorable conditions in 2012, i.e., early sowing date, higher precipitation, and quite mild temperatures, led to a better seed and oil yield and greater aboveground biomass and nitrogen uptake, with the highest amounts being removed by straw. Greater seed yield was found to be associated with a greater plant height and a higher number of capitula per plant. Oil content was negatively affected by the higher temperatures and the lower amounts of precipitation that occurred during the 2012 growing season. Seasonal variation in fatty acid composition depended on the genotype. Lower precipitation and higher temperatures during 2013 favored oleic acid content in high linoleic acid genotypes and linoleic acid in medium to high oleic acid genotypes. Among the genotypes, the linoleic-type Sabina and the oleic-type Montola 2000 performed the best in both seasons. The results, besides identifying promising safflower genotypes for spring sowing in the Mediterranean region and for future breeding programs, pointed out the importance of early sowing to contrast unfavorable environmental conditions during seed-filling, thus ensuring higher yields.

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