Intraplant Variation Research Articles

Chromosome numerical mosaicism in pearl millet (Pennisetum americanum (L.) Leeke)

In pearl millet (Pennisetum americanum (L.) Leeke, 2n = 14), a wide range of intraplant chromosome numerical variation occurring in pollen mother cells at meiosis within the same anther, floret, or spike was found in eight plants. The types of mosaicism encountered were haploid–diploid, diploid–tetraploid, haploid–diploid–aneuploid, and diploid–tetraploid–aneuploid–teloaneuploid. Their probable mode of origin is discussed.Key words: Pennisetum, chromosomal numerical mosaicism.

Heritability of inflorescence and floret traits in gerbera

Heritability, repeatability, and components of variance were estimated for 68 morphological characters describing the inflorescence, scape, and florets of Gerbera hybrida. The heritability estimates were generally moderate to high for simple dimension characters and characters which were the mean of several measurements, low to moderate for ratio and composite characters, and low for enumeration characters and characters describing the intraplant variation of traits. The repeatability estimates were generally low for intraplant variation characters, moderate for simple ratio characters, and largest for composite and mean characters. For most of the characters, the variance among inflorescences from the same plant was the largest portion of the total phenotypic variance.

Chromosome instability in Coix gigantea Koen. (Maydeae)

In Coix gigantea Koen. (2n = 20), six of the plants that survived in the progenies raised from seed collected from Madhya Pradesh showed wide intraplant variation in chromosome number and behaviour. The chromosome number varied from 2n = 7 to 29. Higher configurations involving up to 10 chromosomes were found, though associations of 3 and 4 chromosomes were more prevalent. Univalents were also fairly common. Further, chromosome fragments ranging from one to three per cell were found in several of the cells. Similar variations in chromosome number and fragments were also observed in tapetal cells. Chromosomal associations and chiasma frequency were studied in each of the chromosome classes. Laggards, ranging from one to five were observed at anaphase I and II. Pollen grains were polymorphic and completely sterile, and there was no seed set. The instability was considered as part of the genomic plasticity, coupled with polyploidy, serving to enlarge the cytogenetic diversity in the species. However, it occurs in this population to levels beyond the tolerance limits of the genome affecting the fitness of the individual.Key words: Coix, chromosomal variation.

Introduction to Sources of Intraplant Variation and Consequences for Herbivores

Introduction to Sources of Intraplant Variation and Consequences for Herbivores

Seasonal and intraplant variation of cardenolide content in the California milkweed,Asclepias eriocarpa, and implications for plant defense

Root, stem, leaf, and latex samples ofAsclepias eriocarpa collected from three plots in one population at 12 monthly intervals were assayed for total cardenolide content by spectroassay and for individual cardenolides by thin-layer chromatography. From May to September mean milligram equivalents of digitoxin per gram of dried plant were: latices, 56.8 ≫ stems, 6.12 > leaves, 4.0 > roots, 2.5. With the exception of the roots, significant changes in gross cardenolide content occurred for each sample type with time of collection during the growing season, whereas variation within this population was found to be small. Labriformin, a nitrogen-containing cardenolide of low polarity, predominated in the latices. Leaf samples contained labriformin, labriformidin, desglucosyrioside, and other unidentified cardenolides. In addition to most of the same cardenolides as the leaves, the stems also contained uzarigenin. The roots contained desglucosyrioside and several polar cardenolides. The results are compared with those for other cardenolide-containing plants, and discussed in relation to anti-herbivore defense based on plant cardenolide content. Arguments are advanced for a central role of the latex in cardenolide storage and deployment which maximizes the defensive qualities of the cardenolides while preventing toxicity to the plant.

Studies on the Ecotype of Timothy (Phleum pratense L.) : II. Inter-population variation of intra-plant variations and its relationship with forage yield

Studies on the Ecotype of Timothy (Phleum pratense L.) : II. Inter-population variation of intra-plant variations and its relationship with forage yield

INTRA-PLANT VARIATION IN NUMBER OF SEEDS PER POD AND SEED WEIGHT IN BRASSICA NAPUS ’TOWER’

Field trials were conducted at Saskatoon in 1976, and at Swift Current in 1977, to investigate intra-plant variation in number of seeds per pod and seed weight in Brassica napus L. ’Tower’. Number of pods was greatest on the main raceme, least on the lowest branch. Seed number per pod was also highest on the main raceme, as was seed weight. In 1976, number of seeds per pod and seed weight were higher in pods from the lower half of the main raceme than from those on the upper half. A study of the trends in number of seeds per pod between the end of flowering and maturity revealed a general decline in number of seeds per pod and an increase in the number of aborted seeds at the lower branch positions. At the end of flowering, pods from all branch positions had equal numbers of developing seeds.

Quantitative immunofixation of proteins following zone electrophoresis in agarose gel: Application to the determination of the stoichiometry of the α1-antitrypsin-elastase interaction

A method for the quantitative determination of proteins by immunofixation-agarose gel electrophoresis is described. The proteins are separated electrophoretically and the resulting circular zones overlaid with specific antibody-impregnated filter paper (10.2 μl/cm 2). Following incubation for 20 h at room temperature the plates were processed, stained and the areas of the precipitin zones determined by planimetry. Intra-plate variation (coefficient of variation) for α 1-antitrypsin (30 samples) and elastase (30 samples) at concentrations of 0.25, 0.5 and 1.0 mg/ml was 2.2–5.8% and inter-plate variation ranged from 2.9 to 5.2%. Overall, the analyses showed that the method is the statistical equivalent of rocket immunoelectrophoresis. The lowest concentration used was 0.25 mg/ml which corresponds to a sensitivity of 1.25 μg (5 μl per sample well). It is conceivable that lower amounts could be successfully determined. Application of the method to the determination of the stoichiometry of the α 1-antitrypsin-elastase interaction permitted the simultaneous quantitative determination of inactivated α 1-antitrypsin (an acidic protein) and excess elastase (a basis protein) in α 1-antitrypsin-elastase reaction mixtures (molar ratio elastase/ α 1-antitrypsin = 1.3) and thus by difference, the amount of elastase and α 1-antitrypsin in the α 1-antitrypsin-elastase complex. The results showed that the molar combining ratio of inhibitor to enzyme was 1.086 : 1 or 1 : 1. Conventional inhibition experiments (residual elastase activity as a function of increasing amounts of α 1-antitrypsin) showed this ratio to be 1.79 : 1 but 1.03 : 1 when the inactivation reaction, as determined by quantitative immunofixation, was taken into account. The quantitative immunofixation method should be applicable to interacting systems which, like elastase and α 1-antitrypsin, result in complexes with electrophoretic mobilities intermediate to the parent proteins.

MITOTIC INSTABILITIES IN TETRAPLOID, HEXAPLOID, AND OCTOPLOID BROMUS INERMIS

Mitotic irregularities were observed in the root tip cells at three ploidies, tetraploid (4x), hexaploid (6x), and octoploid (8x), of smooth bromegrass (Bromus inermis Leyss.). These included endomitosis, fragments, chromosomes excluded from the spindle, anaphase bridges, laggards and micronuclei, at different stages of mitosis. High frequencies of anaphase irregularities were detected at the 4x and 6x levels. The commercial octoploid was more stable. Intraplant variations of some morphological characters in smooth bromegrass may be attributed to chromosomal instabilities in somatic cells.

Genetically controlled chromosome numerical mosaicism in pearl millet

In the selfed progeny of a diploid plant ofPennisetum typhoides (Burm) S and H, which was a translocation heterozygote and with chromosome number 2n=13+2 telocentrics, one triploid plant was obtained. In the open pollinated progeny of this triploid, one plant with chromosome numerical mosaicism, chromosome number varying from 2n=28 to 37 of which 23 to 33 normal chromosomes and 3 to 7 telocentrics, was obtained. In PMC meiosis higher associations of 5, 6, 7 or 8 normal chromosomes were observed. This plant was highly sterile. Of the five progeny plants that could be obtained on selfing and open pollination 4 plants showed chromosome numerical mosaicism and one plant had a constant chromosome number of 2n=26+4 telos. As this phenomenon of intraplant chromosome numerical variation can be transmitted from generation to generation it was considered to be genotypically controlled. It was further argued that gene combinations are responsible for the instability and not always associated with higher gene dosage and hence higher polyploidy as suggested by Gildenhuys and Brix in induced amphiploids of Pennisetum. The same factor that was responsible for the chromosome numerical mosaicism seemed to be responsible for the origin of the tetraploid from the triploid.

Lateral variations in the structure of the Philippine Sea Plate

Multiple-filter analysis is applied to surface waves with their paths almost entirely inside the Philippine Sea plate. The resulting dispersion data are used to study the crustal and upper mantle structures of the plate. Effort is made to examine the intraplate structural variations. Part of the Philippine Sea plate appears to have a thin plate thickness of about 30 km and is overlying a very low velocity mantle. Lateral structural variations in the plate are indicated by the dispersion data. The plate can be divided into several elongated regions, all of which are parallel to the eastern plate boundary and each having a rather distinct crustal and upper mantle structure. The active marginal basin region, located immediately to the west of the Mariana trench, probably represents an area of lithospheric generation. This is supported by the very low shear wave velocity, high heat flow, and magmatism. The Kyushu-Palau ridge along the central portion of the plate seems to have a thicker lithosphere, in contrast to its two flank regions, the Philippine basin and the Parece Vela basin.

On the Stomatal Frequency in Barley. : II. Intra-plant variation, vari-etal difference and heritability of stomatal frequency.

Intra-plant variation, varietal difference and heritability of stomatal Lrequency were studied in barley. Stomatal frequency on leaf decreased from flag (L1) to lower leaves. Stomatal frequency on L1 sheath was comparable to that on L4 leaf. Total stomata of awns on one head, estimated from the number of awns per head and the number of stomata per awn, and total stomata on L1 sheath were about as many as those on upper and lower leaf surfaces of flag leaf (Table 3). Cultivars of high stomatal frequency on flag leaf showed higher stomatal frequency on the other leaves and sheaths compared with those of low stomatal frequency on ffag leaf (Fig. 2). Correlation coefficients between stomatal frequency on flag leaf (lower surface) and those on the other leaves or sheaths were high (Table 5). Stomatal frequency on flag leaf (lower surLace) of 384 cultivars differed significantly, ranging from 43 to 95 stomata per mm2. Stomatal frequencies on flag leaf (lower surface) of 7 cultivars grown in two different seasons were highly correlated (r=0. 93) (Fig. 3).

Variation of Chiasma Formation in Populations of <i>Aegilops spoltoides</i>

Chiasma frequency at PMCs was studied in two successive generations of Aegilops speltoides, the one consisting of six populations, the other of four families. Each family was the progeny of a single plant taken from the corresponding population of the first generation.The analysis of data showed significant differences to exist between populations and between families, as well as between plants within populations and families. Among the overall material three subgroups were recognised.The first one, including two populations and the corresponding families, displayed the lowest inter- and intraplant variation of chiasma frequency in both generations, but a more asymmetrical pattern of chiasma distribution was found in families. The next group, represented by one population-family system, dimorphic by constitution, showed similar variability in population and family, with regards to chiasma frequency. The distribution of chiasmata has proven partly similar, including the same proportion of the predominant bivalent type.The third category was the most variable, containing a B-carrying class, in which mean chiasma frequency differed significantly between the two generations, being lower in B-family. The suggestion is that B chromosomes, when accumulated, exert a reducing effect on chiasma formation.

Intra‐Plant Variation for Pollen Production in Male‐sterile and Fertile Alfalfa1

In Medicago saliva L. intra‐plant variation in pollen production occurred in partially male‐sterile clones, but it was not associated with either flower position on the plant or sampling date. The variation occurred at random throughout the plant. Anthers within the same flower varied for both number of pollen grains and percentage of normal pollen grains.The average number of pollen grains per anther varied among clones from about 440 to 850. The free anther had only about two‐thirds as many pollen grains as each of the remaining nine anthers. The number of normal pollen grains correlated with visual estimates of the amount of dehisced pollen, r = .854**, 11 d.f. Pollen abortion in male‐sterile plants apparently reduced internal pressure sufficiently to prevent rupture of the anther wall and extrusion of pollen.

Some Aspects Regarding Behaviour of Supernumerary Chromosomes inAegilops SpeltoidesTausch

SUMMARYProgenies of a B- carrying individual plant found in a particular strain of Aegilops speltoides, were used in an attempt to trace the way whereby B's can be transmitted through EMCs. For comparison, progenies of non-B carrying plants from the same strain and offspring from other strains, without B- chromosomes, were included in the project.According to the results of meiotic observations at PMCs, only the progenies of the B carrier contained supernumerary chromosomes, which probably derived from the female parent, since male parents (grown under common experimental conditions) had been recognised as non-B carriers.In contrast to the maternal plant, which constanly contained a B bivalent, the present material showed considerable inter- and intraplant variation with respect to the number ot B chromosomes. The most frequent cytological configuration was that of PMCs containing 17 chromosomes (7 bivalents plus 3 supernumeraries) and representing the majority of plants and cells. Thus B- chromosomes beh...

Cytogenetics of <i>Saccharum officinarum</i> L., <i>Saccharum spontaneum</i> L. and <i>S. officinarum</i>×<i>S. spontaneum</i> Hybrids

Intraplant variation in chromosome numbers have been reported in the somatic cells of S. officinarum, pollen grains of S. spontaneum and microsporocytes of S. officinarum×S. spontaneum hybrids. The origin of the chromosome mosaics has been traced to the spindle abnormalities caused by genetic factors in the case of S. officinarum, unequal numerical distribution or elimination of univalents during meiosis in S. spontaneum and disturbances in the pre-meiotic mitosis in the interspecific hybrids. It is concluded that the alteration in chromosome numbers in the cells of individual plants followed by vegetative propagation and the functioning of pollen grains with varying chromosome numbers might have played a significant role in the evolution of the extensive euploid-aneuploid series reported in S. spontaneum.

Intraplant instability in smooth bromegrass (Bromus inermis leyss)

Intraplant variation in smooth bromegrass was examined by determining pollen stainability and size in 6 moderately self-compatible S-2, and 12 self-incompatible OP-3 plants. Statistically significant differences in pollen stainability occurred between panicles within plants, between plants, and between plants x within plant interactions. Pollen diameter distributions for OP-3 plants tended to be trimodal, and bimodal distributions occurred in S-2 plants. In trimodal distributions, peaks occurred at known diploid and tetraploid chromosome levels, and it is presumed that the peak between these represented the triploid gametic number.

Intraplant and Interplant Variation of Grain Protein Content in the Parents and the F1 of a Cross of Triticum aestivum L.1

Intraplant and Interplant Variation of Grain Protein Content in the Parents and the F₁ of a Cross of <i>Triticum aestivum</i> L.¹