THE FINE STRUCTURE OF THE GUARD CELLS OF HELIANTHUS ANNUUS

The guard cells of Helianthus annuus contain elements of endoplasmic reticulum and large numbers of mitochondria and dictyosomes. Each guard cell possesses a complex system of small to large vacuoles which contain small, membrane-bound vesicles; the vacuole may actually be one highly invaginated and dissected vacuole extending throughout the cell. A highly developed grana fretwork within the plastids implies full photosynthetic capability and the capability of producing the osmoticulum required for turgor change. No plasmodesmata occur between the sister guard cells or between the guard and epidermal cells. It is postulated that there is a close relationship between plastid development and the presence or absence of plasmodesmata. No microbodies were positively identified in any of the guard cells. Microtubules appear to lie in two planes, thereby giving support to the “two system” observation for microtubules in the guard cells of Pisum sativum.     

EFFECT OF SHORT-TERM SHADING ON THE CYTOLOGY OF PALISADE TISSUE IN MATURE LEAVES OF THE SUNFLOWER HELIANTHUS ANNUUS

Mature sunflower leaves were exposed to partial shading (35 or 14% of normal sun) or darkness (0% of normal sun) for approximately 8 hr. During this period one-half of each test leaf was shaded; the other half was used as a normal sun control. Palisade cell structure from both halves of each leaf was compared. Shading of leaves had little effect on organelle percent volume values (V_v) with exception of the starch compartment which decreased as shading increased. The surface to volume ratio (S_v) of the chloroplast thylakoids increased while the S_v of the mitochondrial membranes decreased as shading increased. Palisade cell volume did not change in shaded portions of the leaf, except in the fully shaded (dark) tissues where cell volume decreased. Changes in the actual volume of organelle compartments were strongly correlated with changes in cell volume. Thus a general osmotic response may account for some of the volume changes associated with differences in light intensity. Shading increased thylakoid surface areas 10–30% over the full sun controls. The ratio of stromal to granal thylakoid surface area remained constant in both the control and partially shaded samples. However, in darkened samples this ratio decreased as stromal membranes increased more than granal membranes. Changes observed in thylakoid surface areas associated with shading did not support thylakoid models which propose the interconversion of granal membranes to stromal membranes and vice versa.     

INVESTIGATIONS ON THE ROOT FORMATION IN THE TISSUES OF HELIANTHUS TUBEROSUS CULTURED IN VITRO

Excised rhizome fragments of Helianthus tuberosus ‘Violet de Rennes’ produce roots in vitro; the sequence of morphogenetic phenomena is as follows: proliferation, differentiation of phloem and tracheids, organization of cambiums, and formation of root primordia from cambiums. This rhizogenesis is conditioned by five limiting factors: mineral salts, sugar, auxin, temperature, and light. The optimum level of each of these factors was determined and in certain cases also the threshold of action. For white light the beginning was about 1/1000 lux. These five limiting factors do not represent the same site of action. The mineral salts, especially nitrogen and calcium, have their effect when the cambiums have been organized. The sugars act before the formation of cambiums. Light operates principally upon cambium and this action is independent of photosynthesis. It was not possible to determine whether the auxin has a preferential site of action. A temperature higher than 15 C is essential to obtain the formation of cambiums but further production of roots is possible at 15 C or even less. The variations in temperature more or less around the optimum stimulate rhizogenesis. The supra-optimal temperatures mainly have their effect before the formation of cambiums and infra-optimal temperatures after. The effect of light can be exhibited at low temperature. Gibberellic acid in association with auxin favors root formation in the dark whereas in light it exhibits inhibiting properties. Rhizogenetic potentialities of tissues are reduced when these are cultured in the dark in presence of auxin. On the other hand, if auxin is applied after the isolation of explants, rhizogenesis is stimulated and the tissues are able to produce roots even in the dark. The action of light and of auxin can be dissociated; when the explants having absorbed a small quantity of auxin are transferred to a medium without auxin for 60 days in the dark, they conserve the rhizogenetic potential which is expressible on transferring them to light. Finally, grafting experiments suggested that light could induce the formation of a rhizogenetic factor in the tissues which is transmittable from cell to cell. These experiments have definitely established that the induction of root formation is governed by several factors which have complex interactions.     

STRESS MODIFICATION OF ALLELOPATHY OF HELIANTHUS ANNUUS L. DEBRIS ON SEED GERMINATION

Helianthus annuus L. variety “Russian Mammoth” was grown in pots, in both the greenhouse and the field, under density treatments of 1, 3, 6 or 12 plants per pot and nutrient treatments of full-strength, ½, ¼, ⅛ or 1/16 strength Hoagland's solution. The plants responded in typical fashion to both nutrient and density stress. Within each nutrient treatment, as the density of planting increased, biomass per pot first increased and then leveled off while biomass per plant decreased. Within each density treatment, as the nutrient level decreased, biomass per pot and per plant decreased. Therefore, both nutrient and density treatments imposed a stress (measured as a reduction in biomass) on individual H. annuus plants. Total phenolic compounds from the Helianthus annuus tissue, expressed as chlorogenic acid equivalents and determined by the PVP method, increased with increasing nutrient stress (i.e., lower nutrient availability); however, increasing density stress failed to significantly modify total phenolic compounds. The maximum total phenolic level determined for field-grown plants (69.70 mg g^-1 tissue) was approximately 58% greater than that found for greenhouse-grown plants (44.16 mg g^-1 tissue). When coarsely ground H. annuus plant material from the stress studies was added to soil, there was a significant depressive effect on germination of Amaranthus retroflexus seeds. In these germination was more closely correlated with total phenolic compounds (chlorogenic acid equivalents) added to the soil by the debris than with any other variable measured. Correlations were best for phenolic values of 200 μg g^-1 soil or greater. Chlorogenic acid (an abundant phenolic acid present in H. annuus) did not inhibit A. retroflexus seed germination when added to soil in pure form. The addition of a nutrient solution to soil containing H. annuus debris reduced subsequent inhibition of A. retroflexus seed germination.     

根癌农杆菌T-DNA在向日葵离体组织中的转移与表达

利用根癌农杆菌B6S3和T37菌株离体感染向日葵切伤的子叶、下胚轴外植体。感染处理的外植体与菌共培养三天后,在无激素条件下以60—96％的频率获得了离体转化的瘤组织。瘤组织在继代培养过程中具有激素自主性生长特性。在无激素培养基上瘤组织的生长速率显著高于正常愈伤组织。所有随机取样测定的瘤组织内均有相应冠瘿碱的存在。     

GENETIC HISTORY AND GENERAL COMPARISONS OF TWO ALBINO MUTATIONS OF HELIANTHUS ANNUUS

Wallace , Raymond H. (U. Connecticut, Storrs.), and Helen M. Habermann . Genetic history and general comparisons of two albino mutations of Helianthus annuus. Amer. Jour. Bot. 46(3) : 157-162. Illus. 1959.—The genetic history of the progeny of a single ultrasonically-treated seedling of Helianthus annuus L. has been summarized for the 6 generations for which quantitative data are available. A yellow mutation was found in the F₂ generation and later in the F₅, a second, white mutation occurred. Both mutants have been grown to maturity by grafting them onto normal green host plants and they have set viable seeds. Both pigment-deficient conditions are inherited as single recessive factors. These albino strains form chlorophyll during their seedling stages if they are grown at low light intensities. Chlorophyll is destroyed, however, under bright illumination and, once bleached, the capacity for chlorophyll formation appears to be lost. The yellow mutant contains xanthophyll but no traces of carotene have been found. In the white mutant, neither carotene nor xanthophyll have been detected. Flower color in the yellow mutant is normal while the flowers of the white mutant have no apparent pigmentation. The growth pattern of grafted yellow mutants is normal, save for a stiffer and woodier condition and a greater resistance to wilting. These characteristics have also been observed in grafted white mutants. In addition, there is a pronounced reduction in leaf size in the white mutant.     

THE VASCULAR TRANSITION REGION OF HELIANTHUS ANNUUS. I. BILATERAL AND UNILATERAL PATTERNS OF DIFFERENTIATION

The vascular transition region of Helianthus annuus L. may exhibit either a unilateral or a bilateral differentiation of primary phloem groups. The unilateral type of transition has been previously described but the bilateral type with its two variations is described here for the first time. The three patterns of transition are compared, and the significance of the variability of transition regions is discussed in terms of basic transition types and phylogenetic importance.     

THE VASCULAR TRANSITION REGION OF HELIANTHUS ANNUUS (COMPOSITAE). II. EFFECT OF IONIZING RADIATION

The vascular pattern in the transition region of Helianthus annuus L. may be altered by ionizing radiation in dosages ranging from 650–19,200 R. The alteration of the vascular cylinder is expressed by (1) the failure of normal tracheary elements to mature and (2) by the induction of accessory xylem and/or phloem strands. The anatomical alterations in the vasculature of the transition region are presented and their significance discussed in terms of seedling survival and the mechanisms controlling vascular differentiation.     

VARIATION OF NUCLEAR DNA CONTENT IN HELIANTHUS ANNUUS (ASTERACEAE)

Nuclear 2C DNA content was determined by laser flow cytometry for 13 diploid (2n = 34) lines (cultivated varieties and inbred lines) of Helianthus annuus. Mean DNA amount of second leaf nuclei varied from 6.01 to 7.95 pg (32%) among lines. Mean DNA content varied up to 19% within lines. Variability in mean DNA content exceeding 27% and 48% was detected among leaves from different nodes of plants of the open-pollinated variety, Californicus, and the inbred line, RHA 299, respectively. The root tip and shoot tip nuclei of H. annuus have been reported to consist of a mixture of aneuploid (17 to 33 chromosomes) and diploid (34 chromosomes) cells, a condition called aneusomaty. Chromosome counts of root tips and an analysis of the distribution of DNA content of large numbers of nuclei from leaves indicate that aneusomaty either does not occur, or is not common, among the lines investigated. The intraspecific, intraline, and intraplant variation in DNA content in H. annuus support the concept that a sizable portion of a plant genome is unstable and subject to rapid changes in DNA amount.     

SHOOT TIP CULTURE OF HELIANTHUS ANNUUS—FLOWERING AND DEVELOPMENT OF ADVENTITIOUS AND MULTIPLE SHOOTS

Shoot multiplication of Helianthus annuus was optimal from half shoot apices cultured on MS media with 0.1–1.0 mg/1 benzyl adenine or kinetin. Auxins inhibited multiplication and promoted callusing. Rooting was poor and was not promoted by auxins. Flowering of multiple shoots was observed after as little as 3 wk of culture. A number of plant growth regulators and environmental conditions had no effect on flowering which supports the determinate apex theory for sunflower (Habermann and Sekulow, 1972). Adventitious shoots were induced on leaves of the multiple shoots in some inbreds.     

VARIATION AND LOCALIZATION OF FLAVONOID AGLYCONES IN HELIANTHUS ANNUUS (COMPOSITAE)

Flavonoid aglycone variation within Helianthus annuus, a species widely distributed throughout North America, was analyzed. Flavonoid aglycones of H. annuus consist of two types, flavones and chalcones. The flavone aglycones are sequestered in glandular trichomes that occur on both leaf surfaces, whereas the chalcone aglycones appear to be incorporated in the waxy leaf cuticle. Considerable variation in flavonoid profile was observed with some plants exhibiting as few as one, and others as many as seven of the eight aglycones detected. No definable phytogeographic patterns were observed for this flavonoid variation. Flavonoid aglycone variation also did not differentiate the infraspecific taxa within H. annuus.