Variation In Leaf Size Research Articles

Effects of sowing date, photoperiod and nitrogen on variation in main culm leaf dimensions in field-grown wheat

In some cereal simulation models, canopy leaf area development is calculated using relationships that summarize how leaf size changes with position. The nature and extent to which various environmental factors interact with ontogenetic variations in leaf size, however, is not clearly understood. This study was undertaken, therefore, to evaluate how temperature, photoperiod and nitrogen impact on leaf to leaf relationships in wheat grown under field conditions. Four contrasting genotypes of wheat comprising two spring and two unvernalized winter types were sown on five dates, supplied with one of two levels of nitrogen (150 kg N ha−1 and 0 kg N ha−1), and grown under natural and extended photoperiod conditions. For the spring wheats, individual mature leaf area increased along with leaf number up to leaf 5 (a stage that coincided with rapid stem elongation) but varied for subsequent leaves in a manner that was dependent on genotype and environment.In the period prior to the expansion of the fifth leaf, neither nitrogen nor photoperiod significantly influenced the pattern of change in leaf size. Thereafter, leaves under low nitrogen and extended photoperiod progressively became smaller, an effect that was due primarily to changes in length rather than in width. For the winter genotypes, which did not reach the stage of rapid stem elongation, mature leaf dimensions increased along with leaf number during the whole period of study and were not markedly affected by photoperiod but, after leaf 5, were smaller for the low nitrogen level. For all genotypes, the size of the first leaf and the coefficients derived by regressing the area of successive leaves on the area of the previous leaf during the vegetative phase varied among sowing dates due partly to the temperature environment under which the leaves at each node developed. The results, however, indicated that the potential leaf size at any of the lowermost leaf positions can be obtained by using a logarithmic function that relates the potential size of one leaf to its predecessor. Such relationship can be used to calculate actual leaf size if account is taken of environmental and assimilate supply factors that operate during leaf expansion. Key words: Wheat, sowing date, leaf area, temperature, photoperiod

Leaf size variation in subterranean clover (Trifolium subterraneum L. sensu lato).

In subterranean clover, leaf size contributes to plant competitivity; besides, this trait is attributed a diagnostic relevance. The study assessed leaf size variation at two growth stages (60 days after sowing and flowering date) on genotypes belonging to the three main subspecies of the complex, viz. subsp. subterraneum, brachycalycinum, and yanninicum. After 60 days, brachycalycinum showed the largest leaflet area while subterraneum and yanninicum did not differ. Leaf size increase between the two measurements, remarkable in all subspecies, was significantly highest in yanninicum, which showed the largest area at flowering date. The leaflet length/breadth ratio was similar in the three subspecies at both stages. In subterraneum and brachycalycinum this ratio decreased significantly from the first to the second measurement; leaflet area increase seemed depending more on breadth than length increase. Yanninicum showed the longest petiole at flowering, and subspecies ranking for this character paralleled that of leaflet area. Particularly in subterraneum, there was a noticeable genotype variation for all characters. Earlier genotypes tended to have larger leaves after 60 days, and shorter petioles and smaller leaves at flowering date. In subterraneum, the genotype leaflet size decreased on increasing altitude and rainfall, and decreasing temperature of the collection sites. The leaf characters examined fairly confirmed to bear a taxonomic basis. Further assessing the physiological behaviour, particularly the response to defoliation and its agronomic implications, of genotypes characterised by different leaf size is envisageable.

QTL analysis to study the association between leaf size and abscisic acid accumulation in droughted rice leaves and comparisons across cereals.

Plants accumulate abscisic acid (ABA) under droughted conditions. Genetic variation in the accumulation of ABA in deteched and partially dehydrated leaves of rice has previously been reported, and this was found to be associated with variation in leaf size (smaller leaves made more ABA). Correlation analysis failed to distinguish clearly between a causal relationship between the two traits and close genetic between loci controlling the traits. Here we present a detailed genetic analysis of ABA accumulation in detached and partially dehydrated rice leaves. using a population of F2 plants generated from the lowland x upland cross IR20 (high-ABA) x 63-83 (low-ABA) which was mapped with RFLP and AFLP markers. Several highly significant quantitative trait loci (QTLs) for ABA accumulation and leaf weight were identified. Only one of the minor QTLs for ABA accumulation (accounting for only 4% of the phenotypic variance) was coincident with any QTLs for leaf size such that the high-ABA allele was associated with smaller leaves. This analysis, therefore, showed that the association previously found between ABA accumulation and leaf size was probably largely due to genetic linkage and not to a direct effect of leaf size on ABA accumulation or vice versa. Because of the importance of ABA accumulation in regulating responses of plants to drought stress and the effects of plant size on the rate of development of stress, QTLs for drought-induced ABA accumulation, leaf size and tiller number were compared between rice and wheat. In particular, a possible location in rice was sought for a homoeologue of the major wheat vernalization responsive gene, Vrn1, as this gene is also associated with major effects on leaf size, tiller number and ABA accumulation in wheat. The likelihood of homoeologous loci regulating ABA accumulation, leaf size and tiller number in the two crops is discussed.

Plant growth-form alters the relationship between foliar morphology and species shade-tolerance ranking in temperate woody taxa

Variation in leaf size (area per leaf) and leaf dry weight per area (LWA) in relation to species shade- and drought-tolerance, characterised by Ellenberg's light (ELD) and water demand (EWD) values, respectively, were examined in 60 temperate woody taxa at constant relative irradiance. LWA was independent of plant size, but leaf size increased with total plant height at constant ELD. Canopy position also affected leaf morphology: leaves from the upper crown third had higher LWA and were larger than leaves from the lower third. Leaf size and LWA were negatively correlated, and leaf size decreased and LWA increased with decreasing species shade-tolerance. Mean LWA was similar for trees and shrubs, but trees had larger leaves than shrubs. Furthermore, all relationships were altered by plant growth-form: none of the qualitative tendencies was significant for trees. This implies the considerably lower plasticity of foliar parameters in trees than those in shrubs. Accordingly, shade-tolerance of trees, having relatively constant leaf structure, may be most affected by the variability in biomass partitioning and crown geometry which influence foliage distribution and spacing and finally determine canopy light absorptance. Alteration of leaf form and investment pattern for construction of unit foliar surface area which change the efficiency of light interception per unit biomass investment in leaves, is a competitive strategy inherent to shrubs. EWD as well as wood anatomy did not control LWA and leaf size, though there was a trend of ring-porous tree species to be more shade-tolerant than diffuse-porous trees. Since ring-porous species are more vulnerable to cavitation than diffuse-porous species, they may be constrained to environments where irradiances and consequently evaporative demand is lower.

Radiation frost susceptibility and the association between sky exposure and leaf size.

Plants growing in exposed and sheltered habitats have characteristic leaf structure and physiology that are traditionally associated with the total amount of incident sunlight. However, greater sky exposure also increases the susceptibility of leaves to radiation frost. Plants with large horizontal broadleaves are particularly susceptible to both overheating during the day and freezing at night. Moreover, the combined effects of high daytime sun-exposure and nighttime frost susceptibility could be particularly stressful to plant tissues. The purpose of this study was to evaluate the influence of elevation and microsite exposure (i.e. net loss of longwave radiation) on frost susceptibility, as well as the corresponding intraspecific variation in leaf size in the subalpine daisy (Erigeron peregrinus). Measured decreases in upper hemisphere infrared radiation (sky IR) of 0.014 W m-2 m-1 occurred with increasing elevation, beyond decreases predicted due to changes in air temperature and water content, resulting in an average decrease of 0.029 W m-2 m-1. Previous equations of sky IR based on air temperature and humidity were improved by adding this elevational term (r 2 improved from 0.52 to 0.71). In contrast, a mean decrease of 6.5 W m-2 m-1 occurred with increasing sky exposure across a subalpine meadow. Leaf size in Taraxacum officinale decreased linearly with increasing elevation and a corresponding decline in sky IR. No difference in daily solar irradiance was measured across the same elevational gradient. Also, E. peregrinus had smaller leaves at high elevation microsites with greater sky exposure and decreased sky IR, while there was a much weaker association between leaf size and the amount of total daily solar irradiance. Differences in plant leaf structure and physiology traditionally associated with daytime sun-exposure may also be influenced by nighttime sky exposure and the susceptibility to radiation frosts.

Image Acquisition, Processing & Analysis in the Biology Laboratory: An Example Using a Macintosh Computer & NIH Image to Quantify Leaf Size Variation within a Tree Canopy

Research Article| March 01 1995 Image Acquisition, Processing & Analysis in the Biology Laboratory: An Example Using a Macintosh Computer & NIH Image to Quantify Leaf Size Variation within a Tree Canopy Robert A. Kistler Robert A. Kistler Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1995) 57 (3): 151–157. https://doi.org/10.2307/4449952 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Robert A. Kistler; Image Acquisition, Processing & Analysis in the Biology Laboratory: An Example Using a Macintosh Computer & NIH Image to Quantify Leaf Size Variation within a Tree Canopy. The American Biology Teacher 1 March 1995; 57 (3): 151–157. doi: https://doi.org/10.2307/4449952 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright 1995 National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

Leaf weight per area and leaf size of 85 Estonian woody species in relation to shade tolerance and light availability

Leaf weight per area (LWA) and leaf size were examined in 85 species of woody plants representing 83% of Estonian native flora. Average values of 68.6 g m −2 for LWA and 6.62 cm 2 for leaf size were estimated for the medium light availability. Mean LWA values can be used to correct for the bias in estimating foliage functional properties in forest stand models and for converting leaf biomass into foliage area. LWA increased with relative light availability (1 minus stand canopy cover) and species light demand, indicating that LWA was higher at the same light availability for more intolerant species. Leaf size is a canopy parameter that should be considered when canopy radiative balance and distribution of solar radiation is of interest. Mean leaf size was not so closely related to light availability as LWA, decreasing with species light demand and increasing with total plant height. Variation in leaf size is discussed in terms of species shade tolerance and height growth.

Morphology, fertility and cross-compatibility of somatic hybrids between Brassica oleracea L. and B. campestris L.

Thirty-one somatic hybrids between a heat tolerant cabbage cultivar ‘Yoshin’ ( Brassica oleracea var. capitata L.) and a Chinese cabbage cultivar ‘Kenshin’ ( Brassica campestris var. pekinensis L.) were obtained with the aim of breeding new Brassica vegetables adapted to tropical areas. After excluding two hexaploid somatic hybrids, 29 individuals were investigated for pollen fertility and seed set after self-pollination and back-crossing with the parental species. All 29 amphidiploid somatic hybrids showed pollen fertility higher than 70%, and 28 set seeds by self-pollination (2.2 seeds per silique). The hybrids were cross-compatible with Chinese cabbage (1.5 seeds per silique), while practically incompatible with cabbage. Progeny lines obtained by self-pollination had larger leaves than, and intermediate leaf shape of, the parental species. The lines obtained by back-crossing with Chinese cabbage showed larger leaves than the parents and similar leaf shape to Chinese cabbage. These progeny lines, on the whole, exhibited an appreciably wide variation in both leaf size and shape. Variation was found also within the lines for leaf shape. The somatic hybrid method, therefore, could provide new genetic variations to be used to develop new vegetable cultivars.

Monitoring physical and chemical properties of freshly harvested field‐grown Aloe vera leaves. A preliminary report

AbstractThe content of total solids was obtained using the homogenate of mesophyll tissue of field‐grown Aloe vera leaves. Filtered gel was used to determine the acidity (pH), content of total reducing sugars and amount of filterable solids. Additional cellulase‐digested and filtered gel was used to determine optical density (for estimating aloin level) and concentrations of calcium and magnesium, as well as for HPLC analysis. There was a considerable variation in leaf size among different production fields. Acidity of the sap was rather consistent, ranging between 4.45 and 4.50. Fibre content, although small, varied by as much as 75%. Profiles of HPLC analyses showed two relatively stable and consistent peaks in nearly all samples that may be used to verify the presence of Aloe extract in an end product, provided these compounds are stable during processing of the Aloe gel.

2 Genetic and Molecular Analysis of Leaf Development

Publisher Summary This chapter discusses the genetic and the molecular analysis of leaf development. The pattern of successive leaves on a meristem, called phyllotaxis, has provided experimental systems for the studies of whole-plant pattern formation. Within the leaf itself, bilateral symmetry, precise and orderly vascular differentiation, and stomata1 patterns within the leaf epidermis all exemplify patterned differentiation. Various hypotheses have been put forward to explain the complex process of pattern generation in plants. The two most prominent hypotheses state: that the genetic mechanisms operate at supracellular levels to generate form and that the patterns are progressively determined in a “differentiation-dependent” manner. Plants often express a heteroblastic variation in leaf shape and size on the axis. It is, therefore, important in developmental studies to have designations for specific leaves. Leaf shape can be studied, by combining the morphological analysis with genetic clonal analysis, utilizing the somatically marked cells and the cellular site of gene action can be elucidated, by combining the clonal analysis with mutational analysis in studies of interactions between mutant and wild-type cells.

Measuring investment in carnivory: seasonal and individual variation in trap number and biomass in Utricularia vulgaris L.

The partitioning of biomass between traps and leaves is a measure of the investment in carnivory of Utricularia vulgaris and is dependent on the relative values of three attributes: trap size, trap number and leaf size. Marked seasonal and individual variations in trap size, trap number and leaf size occur within a small population of U. vulgaris at Wicken Fen, Cambridgeshire, UK, with some plants consistently having fewer traps per leaf than others, and some smaller leaves than others, throughout the growing season. However, the three attributes vary independently, so that all combinations over the observed ranges of trap size, trap number and leaf size occur simultaneously in the population. In spite of the variation in the three constituent factors, the proportion of biomass invested in traps is close to 50% in the majority of plants and throughout most of the growing season. The contribution of traps to total biomass cannot be predicted from the number of traps per leaf. Although the proportion of biomass represented by traps is the most useful measure of a plant's investment in carnivory, the precise way in which the biomass is partitioned between a variable number of traps of different sizes may also be an important consideration in cost-benefit analyses.

PLANT SIZE AND FORM IN THE UNDERSTORY PALM GENUS GEONOMA: ARE SPECIES VARIATIONS ON A THEME?

This study addressed the hypothesis that phylogenetic changes in plant size at reproductive maturity may have facilitated adaptive radiation of Geonoma species within rain forest understory habitats. Leaf size, leaf form, plant size, and growth form were compared within and among 23 species of Geonoma from lowland and montane rain forest areas of Costa Rica and Colombia. Leaf size was significantly correlated with crown height in 18 of the 21 species examined, and with stem diameter in 17 of the species. In species characterized by a gradual ontogenetic transition from bifid to dissected leaves, shoots with bifid leaves were significantly smaller than shoots with dissected leaves with respect to rachis length, number of plications, and stem diameter. Among species, stem diameter below the crown explained 74% of the variation in leaf size (rachis length). Crown height and stem diameter were positively correlated among clustered species, but not among solitary species or all species combined. Leaf dissection was correlated with crown height among the 17 species with dissected leaves; species with bifid leaves were significantly smaller than species with dissected leaves with respect to leaf size and stem diameter. Solitary species had larger leaves and larger stem diameters than clustered species at the same crown heights. Morphological patterns among species generally followed within‐species trends. These patterns suggest that Geonoma species are variants on a generic theme:within and among species, leaf size and complexity of form increase with stem diameter and crown height. Solitary and clustered growth forms appear to be morphologically convergent; within each of these architectural groups, the generic theme still applies. Evolutionary changes in leaf size, leaf form, and plant size, however, have clearly involved other factors in addition to variation in plant size.

Effect of Oak Leaf Size on Abundance, Dispersion, and Survival of the Leafminer Cameraria sp. (Lepidoptera: Gracillariidae)

Patterns of relative densities of a dominant leafmining species, Cameraria sp. ( agrifoliella Braun group), on eight trees of Quercus emoryi Torrey were documented over five growing seasons. Relative abundances tended to remain constant among trees throughout the five growing seasons, and densities were consistently greater in the shaded regions of trees than in the sunny regions. To test the hypothesis that variation in leaf size affects colonization, dispersion, and survival of Cameraria sp., equal numbers of leafminers were introduced into field enclosures and allowed to colonize branches varying in mean leaf size. Densities of leafminers were lower and dispersion was more aggregated on small-leaved branches than on large-leaved ones. Mortality of larval leafminers was either inversely density-dependent or density-independent at the spatial scale of the branch. However, log linear analysis showed that survival of leafminers was a negative function of clumping of leafminers among and within leaves. Small-leaved branches and trees appear to be less susceptible to leafminer attack because adult females deposit fewer eggs overall, and eggs are more frequently laid singly on leaves of inadequate size for development or are more frequently clumped on leaves with competing conspecifics. It is suggested that variation in leaf size, coupled with variation in other morphological and phenological traits, acts as a ceiling on densities of Cameraria sp. on Emory oak at the study site by altering dispersion such that interference and exploitative competition increase.

Variation in Croton capitis-york (Euphorbiaceae)

When Croton capitis-york was originally described (Airy Shaw 1980), two varieties were recognised, var. capitis-york and var. pilosus Airy Shaw. The latter variety was distinguished by the more pilose indumentum on the petioles, lamina nerves and inflorescences. Airy Shaw (1981) subsequently provided some additional brief notes (incorrectly citing the type of C. capitis-york var. pilosus as the type of C. capitis-york) stating that the species was known only from immature fertile material. While undertaking general field collecting in/rainforest communities on Cape York Peninsula, Queensland, Australia, I encountered several populations of Croton capitis-york Airy Shaw in the vicinity of the type locality of C. capitis-york var. pilosus. Some years earlier, John Clarkson had collected fertile male material in the vicinity of the type locality of C. capitis-york (distributed as C. insularis Baill.) and a fruiting collection had also been made further north by Ann Morton. With the availability of this fertile material it is now possible to provide both an amplified description and to examine the status of the two varieties. The character of indumentum used by Airy Shaw to distinguish his varieties in C. capitis-york is very slight and subject to environmental modification. As with other Australian taxa of Croton with white indumentum, e.g. C. phebalioides F. Muell. ex Muell. Arg., C. insularis Baill. and C. stigmatosus F. Muell., there can be considerable variation in leaf size and indumentum development on a single branch, let alone on different trees growing in varying situations. Examination of the much wider range of material now available for C. capitisyork revealed that the distinction of indumentum development could not be used reliably to sort material into the two varieties.

Genotypic and phenotypic variability of Zostera marina on the west coast of North America

The relation between environmental factors and leaf morphology of Zostera marina L. have long been unclear, primarily because the species is intrinsically variable. The common-garden method was used to determine the genetic, environmental, and interaction components of leaf size variation. Zostera marina consists of several ecotypes with a wide range of phenotypic plasticity. Variation in the morphology of Z. marina was of three types: genetic, accounting for 14% across the localities studied; environmental (phenotypic plasticity along temporal and spatial gradients), accounting for 32%; and interaction between genotype and environmental, acounting for 35%. Five ecotypes were described for the North American Pacific coast: Z. marina L. var. izembekensis Backman, Z. marina L. var. typica Setchell, Z. marina L. var. phillipsii Backman, Z. marina L. var. latifolia Morong, Z. marina L. var. atàm Backman. Temporal variation was due to seasonal phenotypic changes in ecotypes. Zostera marina var. izembekensis showed little seasonal morphological changes; Z. marina var. typica demonstrated minor increase in leaf size in spring and summer. Zostera marina var. phillipsii and Z. marina var. latifolia behaved similarly in that leaf size of both increased markedly in spring through early summer. Zostera marina var. phillipsii is adapted to Hood Canal and Puget Sound while Z. marina var. latifolia occupies the outer coast. Zostera marina var. atàm exhibits sexual reproduction exclusively and is specifically adapted to the Gulf of California. Key words: seagrasses, common-garden experiment, ecotypes, morphometrics, genotypes.

The effect of in vitro pretreatments on subsequent shoot organogenesis from excised Rubus and Malus leaves

Shoot regeneration from Rubus leaves was obtained on a medium containing MS salts, vitamins and sugars, Staba vitamins, casein hydrolysate (100 mg l−1) and 10 μM thidiazuron. Shoot regeneration from Malus leaves was obtained on N6 rice anther medium with 5 μM thidiazuron. In vitro pretreatment of source shoots with either colchicine or thidiazuron enhanced the organogenic potential of detached leaves of two Rubus hybrids. The response to colchicine was quadratic and occurred at non-mutagenic concentrations (75–250 μM). The response to thidiazuron was exponential between 0 and 5 μM. When applied as a pretreatment, the effectiveness of several different cytokinins (benzyladenine, thidiazuron, zeatin) at enhancing Malus and Rubus organogenesis was related to the shoot proliferation activity of the cytokinin and to treatment-induced variation in leaf and petiole size.

Effect of Variations in Leaf Size on Morphology and Photosynthetic Rate of Twigs

C02-exchange rates were measured in the dark and at high irradiance on the current season's twigs (the leaf-bearing portion of the stem) of 10 desert species with twigs capable of positive net assimilation of atmospheric CO2, and for 28 species (some from warm desert communities and others from moderate elevation riparian communities bordering the deserts) whose twigs never exhibited positive net assimilation rates. Dark respiration rate of twigs was found to be strongly correlated with leaf size. Some of the causes of this correlation were revealed by harvest data on the current season's shoots of the same 28 species. As leaf size increased, total mass shoot-1 increased and twig diameter increased. This resulted in a decrease in twig surface volume-1 and an increase in twig respiration rate on a surface area basis. Regardless of the magnitude of the respiration rate in the dark, however, the rate of CO2 efflux from twigs which did not achieve positive net photosynthesis was reduced to near zero in the light. This was attributed to photosynthetic recycling of the respired CO2. By recycling endogenous CO2 derived from mitochondrial respiration, the twigs of largeleaved species could achieve rates of twig gross photosynthesis comparable to those of desert species specialized for positive net uptake by the twigs. These observations suggest that scaling relationships between leaf and twig dimensions may have a strong influence on the kind of photosynthetic activity developed in twig tissues. Positive net assimilation of atmospheric CO2 by twigs may generally be restricted to species with small leaves, small twig diameters and low rates of endogenous CO2 production. Since leaf size varies systematically along aridity gradients, some of the observed distribution patterns of species with positive net assimilation in twigs (they are largely restricted to arid and semi-arid environments) may be caused indirectly through allometric relationships between leaves and twigs. Key-words: Allometries, CO2, desert recycling, diameter, leaf, photosynthesis, twig respiration

Aspects of the ecology of the indigenous shrubLeptospermum scoparium(Myrtaceae) in New Zealand

Abstract Geographic variation in leaf size and shape of the widespread and environmentally-tolerant indigenous shrub Leptospermum scoparium (Myrtaceae) was determined from 182 herbarium specimens collected over much ofits natural range. There were significant correlations with geographic and climatic factors — latitude, distance from coast, annual and winter temperatures. Seventeen seedling populations raised in a uniform environment showed that this leaf variation had a significant genetic component as did the variation in form and the age at first flowering. Flowering phenology in four year old plants from seven widely spread sites also differed significantly when grown together. Ecotypic differentiation is therefore clearly indicated in L. scoparium and this is discussed in relation to previous claims and explanations. Sixteen communities dominated by L. scoparium in southern South Island differed in floristics. The density, basal area, age class distribution, and height of the Leptospermum stems also vary, and are correlated with environmental parameters. The eight climax or sub-climax stands of more extreme inland locations are compared with the eight seral stands from moister coastal habitats. A plea is made for L. scoparium communities to be adequately represented in the New Zealand reserves system rather than ignored because of the often aggressive and seral characteristics of Its dominant species.

Leaf Size and Shape Variation Associated with Drought Stress in Rumex acetosella L. (Polygonaceae)

An experiment was conducted to determine if leaves of Rumex acetosella changed size or shape when under drought stress, and if leaves of plants taken from a xeric environment responded differently to drought stress than leaves of plants from a mesic environment. Mean leaf areas were significantly larger in plants from xeric populations in both dry and control treatments. The five largest leaves of each control individual were significantly larger on xeric plants and on those plants whose clone had survived the low moisture stress. Multivariate analyses indicated no leaf shape differences between moisture treatments or between habitat of origin. The results suggest a physiological rather than a morphological basis for drought tolerance in R. acetosella.

Spectrum of Variation in Somaclones of Triploid Ryegrass1

Ryegrass (Lolium spp.) plants regenerated from callus culture were investigated for variation in morphology, chromosome number and fertility. More than 4000 plants were produced from successive subculture of a single callus initiated from a triploid (2n = 21) embryo of hybrid origin, 2x (Lolium multiflorum Lam.‐perenne L.)✕ 4x (L. perenne L.). The first group of plants regenerated from the callus were triploid. However, those obtained from successive callus subculture had chromosome number of 2n = 20,19,18,16,14, and still later regenerates were neartetraploids with 2n = 30, 29, 28, 27, and 26 chromosomes. A number of plants were mosaics with 2n = 21/20,20/19,27/28, 20/30, and 29/30 chromosomes. Some plants had pollen mother cells with variable chromosome number of 2n = 20,40,60,200 and 2n = 19, 38, 57. Meiotic study suggested the presence of reciprocal translocations, deletions, inversions, chromosomal fragmentation and elimination, and polyploidy. Regenerated plants showed wide variation in leaf shape and size, floral development, vigor, and survival. Some plants had novel phenotypes, not produced by conventional breeding. An albino mutant sector of callus produced only albino plants. Regenerated plants originated both via differentiation of shoot primordia and somatic embryogenesis. It is concluded that the observed variation among the regenerated plants resulted primarily from chromosomal instability in the callus subcultures.