Interplant Variation Research Articles

Nectar Amount, Pollinator Visit Duration and Pollination Success in the Mediterranean Shrub Cistus creticus

We have re-examined the nectar status of Cistus creticus, a plant that was previously thought to be an almost exclusive pollen donor. Although attempts to extract nectar with the microcapillary method failed, rinsates of the flower interior yielded considerable amounts of sugar, yet with high interplant variation. Enzymatic microassays revealed that secreted sugar is adsorbed onto the surfaces of the numerous filaments surrounding the nectary, on the dense pubescence of the ovary surrounded by the nectary and on the yellow base of the purplish-pink, free, obovate petals. The conclusion that C. creticus is an efficient nectar donor was further strengthened by video recording the behaviour of bees and by the high frequency of nectar thieves. We propose that the shallow flower shape and the overheating caused by solar tracking facilitate evaporative concentration of nectar. Alternatively (or in addition), the morphological proximity of the nectary to the filaments and the ovary pubescence facilitates adsorption and the capillary action of the cell walls works antagonistically to glass microcapillaries precluding nectar collection. Addition of artificial nectar in the field had no effect on bee visit frequency but it increased visit duration significantly and decreased abortion rates. In addition, seed yield was increased, especially under insect-limited conditions. We conclude that C. creticus is a nectar donor, and that nectar variation in the field may modify pollinator behaviour and affect pollination success and the fitness of the plant.

Evaluation of a Novel Enzyme-Linked Immunosorbent Assay for Detection of Antibodies against Salmonella, Employing a Stable Coating of Lipopolysaccharide-Derived Antigens Covalently Attached to Polystyrene Microwells

Polysaccharides derived from Salmonella typhimurium lipopolysaccharide (LPS) representing the O-antigen factors 1, 4, 5, and 12 and the O-antigen factors 6 and 7 from Salmonella choleraesuis LPS were derivatized with the photoreactive compound anthraquinone and subsequently covalently coupled to microtiter polystyrene plates by ultraviolet irradiation. Both polysaccharide antigens could be coupled simultaneously to the same microtiter plate. The coated surface was used in indirect ELISA for the determination of serum antibodies from pigs infected with bacteria of the two Salmonella groups and from uninfected pigs. This ELISA proved itself by having a good long-term durability and a high degree of reproducibility, including low day-to-day variations and low interplate variations. Furthermore, the ELISA showed good specificity and sensitivity when data were compared with the optical density levels of a panel of pig sera as determined by a conventional ELISA on the basis of passive coating of the two Salmonella LPS antigens (the mix-ELISA). The covalent anthraquinone mix-ELISA shows promise as a stable and durable alternative to the existing conventional ELISA for serological surveillance of Salmonella infections in pigs.

Orderly arrangement of the chromosomes within barley genomes of chromosome-eliminating Hordeum lechleri × barley hybrids

One-hundred and nineteen progeny plants of crosses between one Hordeum lechleri (2n = 6x = 42) accession and the barley varieties 'Wong' and 'Igri' comprised 54 euploids (2n = 28), 8 hyperploids (2n = 29), 46 hypoploids (2n = 22 - 27), and 11 polyhaploids (2n = 21). Giemsa C-banding showed most interplant chromosome variation to be caused by elimination or, more seldom, duplication of barley chromosomes. The chromosomes of 'Wong' were preferentially lost in the order, 1H-4H-5H-3H-7H-2H-6H (5-4-7-3-1-2-6); those of 'Igri' in the order, 1H-3H or 6H-7H or 5H or 4H-2H (5-3 or 6-1 or 7 or 4-2), indicating different patterns of elimination. Over years chromosome elimination may be continuous. Hypoploid genomes of 'Wong' had the chromosomes arranged in the order, 1H-5H-2H-6H-7H-3H-4H (5-7-2-6-1-3-4), with a discontinuity between chromosomes 1H(5) and 4H(4); whereas in 'Igri' the order was (1H)-5H-2H-4H-7H-6H-3H-(1H) ((5)-7-2-4-1-6-3-(5)) with a discontinuity at 1H(5), indicating varietal differences. The patterns of barley chromosome elimination may be derived from chromosome orders. Elimination starts with a chromosome at the discontinuity, continues with the chromosome at the other end of the order, and proceeds more or less alternately towards the middle. In hybrids including 'Wong', duplication affected the two chromosomes situated at either end of barley chromosome order. A few older hybrids with 2n = 21 had three or four H.lechleri chromosomes substituted for as many barley chromosomes suggesting homoeology. Our observations support the hypothesis of an orderly arrangement of the chromosomes within genomes (Bennett 1981), but they do not agree with the idea of one 'natural karyotype' for each species (Bennett 1984b).Key words: Hordeum, interspecific hybrids, C-banding, chromosome elimination, chromosome order.

Crop modelling in horticulture: state of the art

For the last two decades, crop modelling has become a major research tool in horticulture as in other areas of plant production. A reason for such a success is the versatility of this technique. Scientists look for conceptual frameworks, and horticulture has offered original case studies on, e.g. photosynthesis or plant architecture. Engineers want procedures to solve practical problems, and horticulture is a field where yield prediction, policy evaluation or process optimisation can be very important. Horticulture is characterised by a high diversity of cultivation systems and fruit, vegetable and ornamental species. Till now, few of them have been modelled and efforts have focused on a limited number of processes of crop growth and development. The water balance of plants, the uptake of minerals, the interaction with pests, diseases and genetics, the interplant variability, and the formation of product quality have been poorly addressed. To face the challenge of diversity, modellers will certainly have to adopt more generic approaches. For decision making, crop models should be integrated in a model of the whole system under control and connected to a model of the decision system. Even though a lot remains to be done, a major achievement of crop modelling in horticulture has been a significant increase of communication (in terms of concepts and modelling tools) in a field where the high diversity of species and cultivation systems can be an obstacle.

Reproductive Behavior of Artemisia annua in Subtropical North India

ABSTRACT Artemisia annua is a xeromorphic temperate plant that contains promising antimalarial drugs, the sesquiterpene lactone artemisinin and derivatives of this compound. An examination of the growth and flowering behavior of Artemisia annua in the subtropical climate region of India demonstrated the plant grew normally and flowered profusely in the winter cropping season, late October to late April, at Lucknow, India. Considerable inter-plant variation was observed, however, in growth habit and flowering time. Plants could be grouped into four classes: early maturing dwarf, early maturing tall, late maturing dwarf, and late maturing tall. Early maturing plants which flowered in February and March, produced fertile achenes, completing the life cycle in 7 to 8 months. Late flowering plants that flowered in May and June, when the maximum day temperature was over 40°C, produced florets without seeds. The high temperature conditions to which the late flowering plants were exposed, appeared to prematurely dry the stigma. Late flowering plants sprouted branches from the vegetative and flowering parts of the plant during the rainy season.

Callus and Root Development from Leaf Explants of Sugar Beet (Beta vulgaris L.): Variability at Variety, Plant and Organ Level

In this study , the nature of variability observed in previous experiments, when leaf explants of sugar beet (Beta vulgaris L.) were cultured in vitro, was investigated at different levels of classification (i.e., variety, plant and organ). Large differences in rooting capacity were observed when 10 commercial varieties were compared. Significant inter-plant and inter-leaf (intra-plant) variability was found to exist within a variety but explants taken from different positions within the leaf behaved similarly. A two-fold variation in polyphenol-oxidase activity was found within a population of the variety Primo, but no relationship existed between enzyme activity and either root formation or the blackening of the explant tissue when compared by culturing explants taken from the same leaves used for enzyme assays, although a weak negative correlation between the degree of blackening and rooting capacity was observed.

Determinants of pollution abatement in developing countries: Evidence from South and Southeast Asia

Developing countries, paŕticularly those in Asia, are fast adopting industrial pollution control standards similar to those in developed countries. Formal regulation has been greatly hampered, however, by the absence of clear and legally binding regulations; limited institutional capacity; lack of appropriate equipment and trained personnel; and inadequate information on emissions. One would predict highly pollution-intensive production under such conditions. Our research, however, has uncovered strongly contradictory evidence. Despite weak or nonexistent formal regulation, there are many clean plants in the developing countries of South and Southeast Asia. Of course, there are also many plants which are among the world's most serious polluters. What explains such extreme interplant variation? This paper reviews evidence drawn from three empirical studies of plant-level abatement practices conducted 1992–1994. The analyses test the importance of plant characteristics, economic considerations and external pressure in determining environmental performance. The results consistently show that pollution intensity is negatively associated with scale, productive efficiency, and the use of new process technology. It is strongly and positively associated with public ownership, but foreign ownership has no significant effect once other plant characteristics are taken into account. Among external sources of pressure, community action, or informal regulation, emerges as a clear source of interplant differences in all three studies. The results suggest that local income and education are powerful predictors of the effectiveness of informal regulation. They also show that existing formal regulation has measurably beneficial effects, even when it is quite weakly developed.

Bat and hummingbird pollination of an AUTOTETRAPLOID COLUMNAR CACTUS, Weberbauerocereus weberbaueri (Cactaceae)

I present data on flower morphology, pollination, breeding system, and genetic diversity of the columnar cactus Weber‐bauerocereus weberbaueri at 2500 m elevation in southwestern Peru. Weberbauerocereus weberbaueri is a self‐compatible columnar cactus that is visited and pollinated by one species of rare endemic bat, Platalina genovensium, and two species of hummingbirds, Patagona gigas and Rhodopis vesper. W. weberbaueri exhibits pronounced interplant variation in floral color and size, and flowers exhibit traits corresponding to both bat and hummingbird pollination syndromes. Starch‐gel electrophoresis of flower bud tissue indicated that W. weberbaueri is an autotetraploid and that genetic diversity (Hep = 0.257) of the study population was high relative to diploid plants but similar to other tetraploid species. Initial fruit set from pollinator exclusion experiments conducted in 1991 and 1993, at the onset of and after a drought associated with the El Niño event of 1991–1992, revealed that bats were the most important pollinators in 1991, but that hummingbirds and diurnal insects were most important in 1993. In both years, however, autogamy and lepidopteran larval infestation of fruits reduced differences in mature fruit production among pollinator exclusion treatments so that differences in mature fruit set were not statistically significant. Reduced bat pollination in 1993 is attributed to the reduced abundance of bats at the study site during a drought caused by El Niño. I hypothesize that interaction among several factors, including tetraploidy, autogamy, larval infestation of developing fruits, and variation in pollinator abundance, may not result in strong selection for a bat vs. hummingbird floral morph, thus allowing the persistence of floral variation in this cactus.

Effect of variations in seed size and planting depth on emergence, infertile plants, and grain yield of spring wheat

Crop yield can be improved by minimizing plant-to-plant variability in seedling emergence. A study was conducted to determine the effect of variations in seed size and planting depth within a plot on emergence, proportion of infertile plants and grain yield in hard red spring wheat (Triticum aestivum L.). Large seed (40.8 mg kernel−1) was hand planted at 25-, 50- and 75-mm depths, creating three uniform seed size - planting depth treatments. Three other treatments consisted of repeating patterns within the same row: three large seeds and one small seed (23.4 mg kernel−1) at each of 25-, 50- and 75-mm depths. Two additional treatments consisted of 1) three seeds planted 25 mm deep and one seed planted 50 mm deep and 2) three seeds planted 25 mm deep and one seed planted 75 mm deep within the same row. Variation in seed size or planting depth within a row had no impact on percentage emergence, but nonuniform planting depth increased the proportion of infertile plants, mainly as a result of late-emerging plants. On a single-plant basis, mainstem grain yields were relatively uniform, but tiller grain yields were highly variable. When small and large seeds were planted 75 mm deep within a plot, the small-seeded plants produced 34% lower tiller grain yield than neighbouring large-seeded plants, while the large-seeded plants produced 10% higher tiller grain yield than plants from a treatment in which only large seeds were planted. Thus, the variation in seed size within a plot had no impact on total grain yield per plot. When seed was planted at variable depths within a plot, grain yield per plant produced by deep-seeded (75 mm) plants was only 20% of that produced by neighbouring shallow-seeded (25 mm) plants and was only 26% of that produced by plants where all seeds were planted deep (75 mm). Within-plot variation in planting depth increased the proportion of infertile plants (up to 158%) and decreased the grain yield. To maximize grain yield in hard red spring wheat, seed should be planted at uniform, shallow planting depth. Key words: Seed size, planting depth, emergence, fertile plants, interplant variation

Natural rhizobial populations and nodulation status of woody legumes growing in diverse Kenyan conditions

The rhizobial populations and nodulation status of both indigenous (mainly Acacia species) and some introduced woody legume species were assessed under glasshouse conditions in soils collected from 12 sites located in different ecological zones of Kenya. The populations among the sites, as estimated by the MPN technique, varied from 2.3×105 cells g-1 of soil. There were some intrasite variations in population estimates depending on the trap host species, date of soil collection and the method used in sampling the soils. Nodulation in whole soil also varied across the sites with test species frequently showing higher nodulation ability in native soils. Sesbania sesban (L.) Merr. was the most prolific nodulating species while Acacia tortilis (Forsskal) Hayne was very erratic in nodulation. Nodulation of most species showed interplant and intraspecific variability within a single soil source.

Inter- and intra-plant SC length variation in Crepis capillaris

Synaptonemal complexes (SCs) were measured in large samples (16–31) of pachytene nuclei from five different plants of Crepis capillaris, with the aim of conducting a systematic study of intra-plant and interplant SC length variation. Individual plants showed considerable variation in SC length among cells (average range=1.83x), which is presumed to reflect stage-related differences in chromosome and SC length during pachytene. The five plants selected for study showed highly significant differences in SC length. These differences are interpreted as real differences in the means and ranges of SC lengths in different genotypes rather than, for example, sampling effects. Mean SC lengths at pachytene and mean chiasma frequencies at metaphase I show signs of being positively related, but the correlation is statistically non-significant, indicating a need for more extensive study.

Autecological studies on Audouinia capitata (Bruniaceae). 3. Pollination biology

Flower production in Audouinia capitata is highest during the first post-fire season. Self-pollinated flowers produced a mean of only 0.8% fruits bearing seeds. This seed set was increased 17-fold by natural insect-mediated cross-pollination. Hand cross-pollination induced an approximately 5-fold increase in seed set when compared to natural cross-pollination. Germination and initial pollen tube growth are normal following self- as well as cross-pollination. Selfing, however, is characterized by abnormal pollen tube growth at the stylar base, resulting in cessation of growth except in the case of occasional pollen tubes. By one week after cross-pollination, pollen tubes have penetrated the egg apparatus. Average in vitro germination of pollen and frequencies of small underdeveloped microspores in 20 populations varied from 2.5 to 28.4% and from 2.0 to 23.7%, respectively, with large interplant variations within populations in both germination (0 – 79.6%) and underdeveloped microspores (0 – 61.0%). The prevalence of non-viable pollen and insufficient insect-mediated transfer of pollen between the plants which have an insignificant ability to produce seed following self-pollination, are limiting factors in reproduction.

Consistent Interplant Variation in Nectar Characteristics of Mirabilis Multiflora

The volume and sugar content of nectar produced by flowers can affect plant reproductive success by influencing pollinator foraging behavior. Because temporally varying environmental factors can affect nectar characters, the likelihood of pollinator—mediated selection for nectar characters may be reduced. To determine the constancy of interplant variation in floral nectar, I measured the volume and sugar concentration of nectar produced by plants in a population of Mirabilis multiflora within and between seasons. The means and relative ranking of nectar characters varied widely among plants. The means were remarkably constant within a season and across three successive flowering seasons. Variation among plants in sugar produced per flower was significantly correlated with the number of flowers produced (° = 0.29) and sugar concentration of nectar was significantly correlated with the date of peak flowering (° = —0.33). Ramets of clones had similar nectar volumes and total sugar produced, while genetically distinct near neighbors did not, suggesting a genetic component to nectar production. I conclude that plants of M. multiflora vary widely, and consistently through time, in their nectar characters and that this variation could affect pollinator behavior.

Seasonal variation of coumarin and flavonoid concentrations in persistent leaves of wyoming big sagebrush ( Artemisia tridentata ssp. wyomingensis: Asteraceae)

Phenolic substances present in persisent leaves of 10 wyoming big sagebrush plants ( Artemisia tridentata Nutall ssp. wyomingensis Beetle & Young; Asteracae), growing wild from an unknown seed source were monitored over a two-year period to determine intraplant, interplant and seasonal variations in concentration using high performance liquid chromatography (HPLC). Phenolics in extracts of whole flowers were also monitored from early development to senescence during year two. Up to 36 compounds were separated in the extracts and the identified constituents included a large array of coumarins and flavonoids. Statistical analyses of the data indicated that 53% of the individual phenolics present in persistent leaves varied significantly over two years at P ≥ 0.05. However, during the four-month period of flower development, concentrations of only 39% of the phenolics varied significantly in persistent leaves. A posteriori tests performed on the 11 most highly variable phenolics over the two years showed that the variation in concentration occurs between seasons and not within. The results also revealed that intraplant variability was lower than interplant variation, and interplant variability in concentrations was generally equal to seasonal variability over two years. Thus, the observed seasonable changes of phenolic concentrations in persistent leaves were found to be relatively consistent and predictable both from season to season and from year to year.

Interspecific variation of phenolic concentrations in persistent leaves among six taxa from subgenus Tridentatae of Artemisia (Asteraceae)

High performance liquid chromatography was used to determine interspecific differences in relative concentrations of individual coumarin and flavonoid compounds present in the persistent leaves of six Artemisia L. taxa from subgenus Tridentatae (McArthur), tribe Anthemideae, family Asteraceae. An internal standard technique provided an integrated area profile characteristic of each taxon and allowed relative quantification of up to 34 compounds present in the extracts. Sagebrush samples were collected during 1984 and 1986 from various locations and seasons throughout northern Nevada. Subsequent discriminant analysis performed on relative concentrations among 31 phenolic constituents in the extracts for these six taxa revealed 100% classification agreement to morphological identifications. Two-way (species-by-plants) ANOVA indicated that all significantly variable phenolic concentrations arose from interspecific differences. Interspecific variability in phenolic concentrations among these six taxa appears to be greater than interplant, geographic, or seasonal variation. Whether or not interspecific differences in phenolic concentrations among these six taxa represent genetic or environmental influences has not yet been determined.

Acute Effects of Acidic Fog on Photosynthetic Activity and Morphology of Phaseolus lunatus

Acute effects of high-nitrate/low-sulfate acidic fogs with a pH of 2.5 and 3.0 were investigated on 3.5to 4-week-old Phaseolus lunatus L. in a series of replicated trials. After 24 hours, CO2 assimilation rates of primary leaves were reduced by at least one-third by 3-hour fogs with a pH value of 2.5 as compared to control plants treated with a fog of pH 6.3. A 3-hour fog at pH 3.0 reduced C0 2 assimilation a minimum of 20%. Stomatal resistance increased in primary leaves of plants exposed to an acidic fog of pH 2.5 by > 37% compared to plants subjected to pH 6.3 fogs. StomataI resistances in leaves exposed to pH 3.0 fogs increased at least 27%. However, internal CO2 concentrations were not significantly different between controland acidfogged plants at any pH. Standardizing plants for similar CO2 assimilation rates allowed statistical separation of photosynthetically important variables as compared to unstandardized experimental designs with higher interplant variability. Methacrylate plastic sections of foliar lesions resulting from exposure to pH 2.0 fogs revealed that damage usually progressed vertically from the upper to lower epidermis. Xylem was less susceptible to damage than other tissues.

Seed quality, cotyledon elongation at suboptimal temperatures, and the yield of onion

AbstractCotyledon length in onion (Allium cepa, cv. White Lisbon) was linearly related to time from radicle emergence until the formation of the cotyledon hook, but thereafter increased exponentially with time. Within each phase the rate of cotyledon elongation was linearly related to temperature, and these relations were similar among seeds from several percentiles of the germinating populations of three contrasting seed lots. The mean base temperature was 1.4°C. These thermal time relations closely predicted the elongation of cotyledons of seedlings from cohorts of early- and lategerminators from a further lot of this cultivar at two suboptimal temperatures. Eleven cohorts of seedlings from seeds of differing quality were transplanted to the field on both the same date and at the same time from visible germination. The plants were harvested 59 days later. No effect of seed quality on mean plant weight, mean bulb diameter, or interplant variation in bulb diameter was detected. It is concluded that the rate of pre- and post-emergence seedling growth in onion is independent of environmentally induced differences in seed quality (seed vigour). Thus, any effect of this factor on plant size or crop yield, at a given density, is solely a function of time to germinate.

Effect of Variegation in Euonymus japonica var. aureus on Two Phloem Feeding Insects, Unaspis euonymi (Homoptera: Diaspididae) and Aphis fabae (Homoptera: Aphididae)

Compared with green plants, variegated plants compensated for the reduced photosynthetic efficiency of each leaf by producing more leaf area per unit of biomass. This altered growth pattern indicates that nutrients must be more mobile in variegated plants to support the new leaf growth. The movement of plant nutrients, such as nitrogen, has been linked to the performance of several phloem feeding insects. The fecundity of two phloem feeding insects was examined to determine if factors that increased nitrogen movement could improve their performance. The fecundity of Unaspis euonymi and Aphis fabae was observed, respectively, on stems and leaves of variegated and green Euonymus japonica var. aureus. Fecundity of both phloem feeders was improved on the variegated plants. In addition to examining interplant variation in suitability, intraplant variation was examined for A. fabae. Young variegated leaves provided the most suitable substrate for this insect. These data suggest that horticulturally important attributes such as variegation can affect the susceptibility of ornamental plants to insect pests. Variegation alters normal patterns of growth and nutrient transport in a manner that suggests an increased flux of mobile nutrients. These changes are likely to enhance the fecundity of associated sucking insects such as aphids and scales.

Genetic studies of corn (Zea mays L.) anther culture response

Anthers of two maize (Zea mays L.) inbred lines, DBTS (P1) and B73 (P2), their F1, F2 and first backcross generations - F1 x DBTS (B1), and F1 x B73 (B2) - were float cultured in YP medium to study the inheritance of corn anther culturability using generation mean analysis. Significant effects of generation were observed for the three traits measured: anther response (%), frequency of embryos (%) and anther productivity. Variation among the generations was similar for anther response and frequency of embryos: no significant differences were found among the P1, F1, F2 and B1 means, but the means of P2 and B2 were significantly lower than those of the other generations. For anther productivity, the F2 generation tended to have a slightly higher tendency for multiple embryo formation. A simple additive-dominance model was adequate in explaining the inheritance of anther response and frequency of embryos, but digenic epistasis (additive x dominance) was involved in the inheritance of anther productivity. Additive genetic variance was higher than non-additive genetic variance for all the traits; however, only environmental variance was significant. Narrow-sense heritability estimates were 65% and 75% for anther response and frequency of embryos, respectively. Significant inter-plant variation was observed within generations, even for the inbred line DBTS, but isozymic analysis involving five enzyme loci did not reveal any genotypic variability within the inbred lines DBTS and B73.

EVIDENCE OF PARTIAL APOMIXIS IN ANTENNARIA MEDIA (ASTERACEAE: INULEAE) DETECTED BY THE SEGREGATION OF GENETIC MARKERS

The interplant variation in sexual and asexual reproduction in an Oregon population of the alpine perennial Antennaria media was investigated. Four polymorphic loci were assayed by enzyme electrophoresis of the progeny of 72 families from two subpopulations of A. media. The population was divided into two spatially distinct subpopulations. A multilocus model, incorporating a mixture of apomixis and random outcrossing, was used to estimate the mating system of pistillate plants both on the population and individual levels with statistical significance of the estimates based on bootstrap methods. The population contained a mixture of sexual individuals, partial apomicts, and obligate apomicts. The first subpopulation contained individuals that were partially apomictic and presumably produced both reduced and unreduced embryo sacs. There was a conspicuous difference in the breeding system composition between the two subpopulations. The first subpopulation had a “female” biased gender ratio and contained mostly obligate apomicts, some partial apomicts, and some outcrossing amphimicts. The second subpopulation, which had a nearly balanced gender ratio, contained mostly amphimicts, some obligate apomicts, but no facultative apomicts. This is the first study to document partial apomixis in individual plants by the use of genetic markers.