A Theory for Circumnutations in Helianthus annuus

A theory is given for circumnutations in plants, especially hypocotyls of Helianthus annuus, which were used as experimental material The theory is based on the lateral auxin transport, which arises when a gravitational force component acts on the plant. With a suitable time delay between stimulus and response, oscillations or circumnutations should arise. It is possible to describe these oscillation phenomena by the solutions of a differential equation, derived in this paper. The time delay has a central role in this equation. The time delay is assumed to be identical with the geotropic reaction time for the hypocotyls. The ratio between the periodic time for the circumnutations and the reaction time for geotropic curvatures was found to be approximately constant in the temperature region investigated (namely 15–40°C), which supports the theory. Different methods of recording the circumnutations were used, 8 mm film camera technique being the most frequently employed. The introduction of a weighting function for describing the plants “memory” of the stimulation makes it possible to relate the periodic time of the circumnutations to the reaction time for geotropic curvatures. The necessity of this weighting function as well as of the time delay in the equations is emphasized. An explanation of the “Fünfphasen-bewegungen”, reported in the literature, is presented.     

A microsatellite marker in Helianthus annuus L.

The importance of genetic polymorphism detected by microsatellites is now well established in mammalian genomes. Sequences with a CA repeat, specific to sunflower, Helianthus annuus L., were found by screening a genomic library in M13. After amplification, some polymorphism was detected on these sequences within a sample of cultivars and populations.     

Diffusible gibberellins and phototropism in Helianthus annuus

Summary Endogenous gibberellins were obtained in agar from the lower cut surface of upright sunflower shoot-tips. Exposure to unilateral light of the tips standing on agar, with the lower cut ends bisected by a vertical glass barrier at right angles to incident light, resulted in approximately 8 times the quantity of gibberellins moving into the agar below the shaded side than into the agar below the illuminated side. These results are similar to those reported earlier for gibberellins and geotropism in sunflower shoots, and suggest than the development of both light-and gravity-induced growth curvatures involve an asymmetry in gibberellin distribution across elongating internodes.     

Natural variation in gene expression between wild and weedy populations of Helianthus annuus

The molecular genetic changes underlying the transformation of wild plants into agricultural weeds are poorly understood. Here we use a sunflower cDNA microarray to detect variation in gene expression between two wild (non-weedy) Helianthus annuus populations from Utah and Kansas and four weedy H. annuus populations collected from agricultural fields in Utah, Kansas, Indiana, and California. When grown in a common growth chamber environment, populations differed substantially in their gene expression patterns, indicating extensive genetic differentiation. Overall, 165 uni-genes, representing approximately 5% of total genes on the array, showed significant differential expression in one or more weedy populations when compared to both wild populations. This subset of genes is enriched for abiotic/biotic stimulus and stress response proteins, which may underlie niche transitions from the natural sites to agricultural fields for H. annuus. However, only a small proportion of the differentially expressed genes overlapped in multiple wild vs. weedy comparisons, indicating that most of the observed expression changes are due to local adaptation or neutral processes, as opposed to parallel genotypic adaptation to agricultural fields. These results are consistent with an earlier phylogeographic study suggesting that weedy sunflowers have evolved multiple times in different regions of the United States and further indicate that the evolution of weedy sunflowers has been accompanied by substantial gene expression divergence in different weedy populations.     

Genetic characterization and molecular mapping of a chlorophyll deficiency gene in sunflower (Helianthus annuus)

A major gene controlling chlorophyll deficiency (phenotyped by yellow leaf color, yl) in sunflower was identified and mapped in an F(2) population derived from a cross between two breeding lines. Greenness degree was scored by a hand-held chlorophyll meter in the F(2) population. Leaf tissue from the parents, F(1) hybrids, and some F(2) progenies were also sampled to determine the chlorophyll content. All F(1) plants had normal green leaf color and the segregation of the plants in the F(2) population fits the monogenic ratio (chi((3:1))(2)=0.03, p>0.9), indicating that leaf color is a monogenic trait with normal green dominant over yellow leaf color in this population. The contents of chlorophyll a, chlorophyll b, and total chlorophyll in the yellow-leafed lines were reduced by 41.6%, 53.5%, and 44.3%, respectively, in comparison with those in the green-leafed lines. Genetic mapping with molecular markers positioned the gene, yl, to linkage group 10 of sunflower. An SSR marker, ORS 595, cosegregated with yl, and a TRAP marker, B26P17ga5-300, was linked to yl with a genetic distance of 4.2cM. The molecular marker tightly linked to the chlorophyll deficiency gene will provide insight into the process of chlorophyll metabolism in sunflower.     

Characteristics of action potentials in Helianthus annuus

The action potentials induced by nondamaging electrical stimuli in 16- to 22-day-old plants of Helianthus annuus were examined. Typical recordings are presented. Mean values of their amplitudes and conduction velocities in the stem, the strength-duration relation, the 'all-or-none' law and the refractory periods have been determined. The amplitude and velocity of propagation were essentially identical in the upward and downward direction, but greater in the upper than in the lower half. In 'electrically active' plants, the rheobase value is 2 V, the minimum period for stimulation is 1.8 s. and the chronaxie 2.3 s. It is noted that the excitability level between similar plants on the same day and in the same plant on different days is highly variable and undergoes periodic changes.     

A point mutation in the photosystem I P700 chlorophyll a apoprotein A1 gene confers variegation in Helianthus annuus L

Plant Molecular Biology - CRISPR-edited variants at the 3′-end of OsLOGL5's coding sequence (CDS), significantly increased rice grain yield under well-watered, drought, normal nitrogen,...     

Mapping one of the 2 genes controlling lemon ray flower color in sunflower (Helianthus annuus L.)

In an F2 population of 120 plants derived from a cross between 2 breeding lines with yellow ray flowers, we observed 111 plants with yellow-colored and 9 plants with lemon-colored ray flowers. The segregation pattern fits a 15:1 (chi2(15:1) = 0.32, P > 0.5) ratio, suggesting that the lemon ray flower color is conditioned by 2 independent recessive genes that had been contributed individually by each of the parents. We sampled 111 plants from the 3 F(2:3) families displaying a 3 to 1 segregating ratio for genotyping with molecular markers. One of the genes, Yf(1), was mapped onto linkage group 11 of the public sunflower map. A targeted region amplified polymorphism marker (B26P17Trap13-68) had a genetic distance of 1.5 cM to Yf(1), and one simple sequence repeat marker (ORS733) and one expressed sequence tag (EST)-based marker (HT167) previously mapped to linkage group 11 were linked to Yf(1) with distances of 9.9 and 2.3 cM, respectively.     

A comparison of the water relations characteristics of Helianthus annuus and Helianthus petiolaris when subjected to water deficits

The effect of water deficits on the water relations and stomatal responses of Helianthus annuus and Helianthus petiolaris were compared in plants growing in the glasshouse under controlled conditions. Unirrigated plants of both genotypes were subjected to two different stress rates in which predawn leaf water potentials declined steadily at either 0.15 MPa day^?1 or 0.50 MPa day^?1. In both genotypes water stress induced a gradual and similar decrease in leaf conductance from 1.6 to 0.3 cm s^?1 as water potential decreased from-0.5 to-2.0 MPa. The relationship between leaf conductance and leaf water potential was not affected by the rate of stress development. Development of predawn leaf water potentials of-1.3 MPa had no significant effect on the relative water content at zero turgor, the apoplastic water content or the volumetric elastic modulus of whole leaves in either species, but decreased the osmotic potential at full turgor and zero turgor by 0.22 MPa and decreased the turgid weight: dry weight ratio from 10.6 to 8.4 in H. annuus, but not in H. petiolaris. In H. annuus leaves expanded during stress development, changes in the osmotic potential at full turgor induced by water deficits did not disappear on rewatering.     

Molecular mapping of a nuclear male-sterility gene in sunflower (Helianthus annuus L.) using TRAP and SSR markers

A nuclear male-sterile mutant, NMS 360, induced by streptomycin from an inbred maintainer line HA 89, possesses a single recessive gene, ms9, controlling male sterility. The present study identified DNA markers linked to the ms9 gene in an F₂ population derived from the cross of NMS 360 × RHA 271 and maps the ms9 gene to an existing sunflower SSR linkage map. Bulked segregant analysis was performed using the target region amplification polymorphism (TRAP) marker technique and the simple sequence repeats (SSR) technique. From 444 primer combinations, six TRAP markers linked with the ms9 gene were amplified. Two markers, Ts4p03-202 and Tt3p09-529, cosegregated with the ms9 gene. The other four markers, To3d14-310, Tt3p17-390, Ts4p23-300, and Tt3p09-531, linked with ms9 at a distance of 1.2, 3.7, 10.3, and 22.3 cM, respectively. Thirty SSR primers from 17 linkage groups of a PHA × PHB cultivated sunflower linkage map were screened among the two parents and the F₂ population. SSR primer ORS 705 of linkage group 10 was tightly linked to ms9 at a distance of 1.2 cM. The ms9 gene was subsequently mapped to linkage group 10 of the public sunflower SSR linkage map. The markers that were tightly linked with the ms9 gene will be useful in marker-assisted selection of male-sterile plants among segregating populations, and will facilitate the isolation of the ms9 gene by map-based cloning.     

A regeneration protocol for sunflower (Helianthus annuus L.) protoplasts

Summary Hypocotyl protoplasts of four different Helianthus annuus genotypes were cultivated for 22–28 days in agarose droplets covered with liquid medium. In the first week, supplementation of the medium with plant growth regulators was at a 0.8/1 ratio of cytokinin and auxin followed by a high auxin concentration in the second week and a cytokinin to auxin ratio of 8/1 in the third and fourth week. Following transfer onto solid medium containing cytokinin and auxin in a proportion of 40/1 morphogenic callus started to form globular structures that developed into leaf primordia. Subsequent shoot elongation and rooting were obtained on hormone free medium after dipping the cut shoots into high auxin solution. Thirteen weeks after protoplast isolation, plantlets could be transferred to the greenhouse. Shoot regeneration was obtained for all four cultivars (Florom-328, Cerflor, Euroflor, Frankasol) at different rates reflecting their regenerative potential.Abbreviations BAP 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - FeNaEDTA ethylenediamine tetraacetic acid ferric sodium salt - IAA indole acetic acid - MES morpholinoethane sulfonic acid - NAA 1-naphtalene acetic acid     

Complex relationship between growth and circumnutations in Helianthus annuus stem

The growth and circumnutation of the stem of three-week old Helianthus annuus in the 16:8 h light:dark photoperiod were monitored using an angular position-sensing transducer and a time lapse photography system. It was found that the rate of growth and circumnutation reached a high level in the dark stage; in the light stage, however, only the growth rate reached the same high level, whereas the circumnutations were weak. These results showed that in the light stage the stem circumnutation was downregulated more strongly than the growth. Short-term stem responses to darkening and illumination were a further display of the relation between growth and circumnutations. Switching off the light caused an increase in the growth and circumnutation rate. In some cases it was accompanied by changes in the rotation direction. On the other hand, switching the light on caused an immediate transient (several-minute long) decrease in the growth rate resulting in stem contraction, and this was accompanied by an almost complete pause of circumnutation. Additionally, under light, there occurred a subsequent decrease in the magnitude, disturbance of circumnutation trajectory and, in some cases, changes in the direction of rotation. The observed stem contraction and disturbance of circumnutation imply the occurrence of turgor changes in sunflower stem, which may be caused by a non-wounding, darkening or illumination stimulus. Our experiments indicate that the disturbances of the growth rate are accompanied by changes in circumnutation parameters but we have also seen that there is no simple quantitative relation between growth rate and circumnutation rate.Key words: Helianthus annuus, plant movement, circumnutation, elongation, growth, stem contraction     

向日葵单子叶和三子叶突变体的形态特征

Phyllotaxis and morphological characteristics of monocotyledonous and tricotyledonous mutants ( found during cultivation process) and dicotyledonous plants of Helianthus annuus Linn. were observed. The results show that numbers of monocotyledonous, dicotyledonous and tricotyledonous plants are 8, 339 and 3, respectively in 350 cultivated plants of H. annuus, accounting for 2. 3%, 96. 9% and 0. 9% of total individual number, respectively, and their corresponding phyllotaxis is alternate, opposite and whorled types, respectively. Monocotyledonous plant has the fewest leaf number, the most leaf layer number, and the largest flower diameter; tricotyledonous plant has the most leaf number, the fewest leaf layer number, and the smallest flower diameter. There is no obvious difference in plant height of individuals with different cotyledon types. It is suggested that cotyledon number of H. annuus is obviously correlated with phyllotaxis type.     

Ethylene-Mediated Regulation of Gibberellin Content and Growth in Helianthus annuus L

Elongation of hypocotyls of sunflower can be promoted by gibberellins (GAs) and inhibited by ethylene. The role of these hormones in regulating elongation was investigated by measuring changes in both endogenous GAs and in the metabolism of exogenous [³H]- and [²H₂]GA₂₀ in the hypocotyis of sunflower (Helianthus annuus L. cv Delgren 131) seedlings exposed to ethylene. The major biologically active GAs identified by gas chromatography-mass spectrometry were GA₁, GA₁₉, GA₂₀, and GA₄₄. In hypocotyls of seedlings exposed to ethylene, the concentration of GA₁, known to be directly active in regulating shoot elongation in a number of species, was reduced. Ethylene treatment reduced the metabolism of [³H]GA₂₀ and less [²H₂]GA₁ was found in the hypocotyls of those seedlings exposed to the higher ethylene concentrations. However, it is not known if the effect of ethylene on GA₂₀ metabolism was direct or indirect. In seedlings treated with exogenous GA₁ or GA₃, the hypocotyls elongated faster than those of controls, but the GA treatment only partially overcame the inhibitory effect of ethylene on elongation. We conclude that GA content is a factor which may limit elongation in hypocotyls of sunflower, and that while exposure to ethylene results in reduced concentration of GA₁ this is not sufficient per se to account for the inhibition of elongation caused by ethylene.     

Ent-Kaurene Biosynthesis in Extracts of Helianthus annuus L. Seedlings

Kaurene synthetase B activity (conversion of copalyl pyrophosphate to ent-kaurene) is readily detectable in crude cell-free extracts of 3- to 4-day old dark-grown sunflower (Helianthus annuus cv. Mammoth) seedlings, whereas little or no kaurene synthetase AB activity (conversion of geranylgeranyl pyrophosphate to ent-kaurene) can be found in these extracts under comparable assay conditions. A low amount of AB activity is evident only if an extensively dialyzed extract is used in low concentrations as the enzyme source. One factor which may contribute to the low apparent levels of AB activity is the presence of inhibitory factors in the crude sunflower extract since these extracts can be shown to act as a potent inhibitor of Marah macrocarpus endosperm kaurene synthetase AB activity. Heat treatment (100°C) or dialysis of the sunflower extract reduces the amount of its inhibitory activity. Also, it was observed that low concentrations of extensively dialyzed sunflower extracts act to stimulate M. macrocarpus AB activity. There is no evidence for the presence of an inhibitory factor for M. macrocarpus kaurene synthetase B activity in sunflower extracts. However, there does appear to be present in the crude preparation of sunflower extract a dialyzable factor(s) that impedes its own B activity. There is little information to date on the nature of these inhibitory and stimulatory factors for kaurene synthetase activity or their possible roles in physiological regulation. The possible presence of such factors should be considered, however, when attempting to evaluate kaurene synthetase activities in extracts of vegetative plants.     

Characterization and mapping of a downy mildew resistance gene,Pl36, in sunflower (Helianthus annuus L.)

Molecular Breeding - Leaf thickness is an important trait in rice (Oryza sativa L.). It affects both photosynthesis and sink-resource efficiency. However, compared to leaf length and length width,...