Comparative effect of silver ion and gibberellic acid on the induction of male flowers on femaleCannabis plants

Summary Silver ion applied as AgNO₃ to the shoot tip of female plants ofCannabis induces male flowers. It is more effective than gibberellic acid (GA₃) in maintaining the induced state.Acknowledgment. G.S. thanks the Council of Scientific and Industrial Research, New Delhi, India, for the award of a Junior Research Fellowship.     

Anthocyanins in iris flowers

Summary 6 kinds of anthocyanin have been found in the flowers of 5 iris species. They were identified as the 3-p-coumaroyl-rutinosido-5-glucosides and the 3-rutinosido-5-glucosides of malvidin, petunidin and delphinidin. The distribution pattern of the iris-flower pigments is discussed; it shows thatIris species belonging to the section Apogon differ from the plants of the sections Xiphium and Eupogon owing to the occurrence of malvidin glycosides in addition to delphinidin glycosides.The author thanks Prof. K. Hayashi for his valuable advice and Mr E. Yamamoto for his help during the course of this work.     

On the distribution of phytoecdysteroids in plants

The occurrence and levels of phytoecdysteroids in the seeds and other parts of plants grown from the seeds of 180 randomly selected plant species were assessed and compared. Ecdysteroids are frequently detectable in leaves and flowers, but less so in stems, roots and seeds. The seeds of 290 species were assessed for the presence of hydrolysable ecdysteroid conjugates. Low levels of conjugates were detected in a significant number of species, large amounts being present only when levels of free ecdysteroids were high. Individual plants of Arabidopsis thaliana were assessed for the presence of phytoecdysteroids. While plants of this species are generally ecdysteroid negative, individual plants in the population accumulate low levels of ecdysteroids. Extracts of seeds of 50 "ecdysteroid-negative" species were concentrated and partially purified to determine if they possess ecdysteroids at levels below the usual detection levels. Ecdysteroids were detectable by radioimmunoassay in almost all of these concentrated samples. Thus, all lines of evidence point to the conclusion that all species of plants have the capacity to produce at least low levels of phytoecdysteroids. This has important implications for the protection of crop species through enhancing ecdysteroid levels by breeding/genetic modification strategies. Received 2 April 2001; received after revision 4 May 2001; accepted 22 May 2001     

Anthocyanins in the flowers of European orchids

Summary The flowers of European orchids contain cyanidin 3-monoglucoside, cyanidin 3-diglucoside and cyanidin 3,5-diglucoside. 2 complex anthocyanins, composed of cyanin and a 2nd organic compound were isolated from the flowers ofOrchis, Dactylorhiza andGymnadenia.     

Pollen-collecting by stingless bees on cacao flowers

Summary Stingless bees (Trigona jaty) routinely visit the flowers ofTheobroma cacao (Sterculiaceae) in the Atlantic lowlands of Costa Rica. The bees collect pollen and behave as pollen thieves in flowers well exposed to direct sunlight in cacao plantations, and avoid flowers in heavy shade. Pollination rates are maximized, however, in heavy shade due to the high abundance of the small-bodied pollinating midges (Ceratopogonidae and Cecidomyiidae) found in such places. Pollen-thieving by stingless bees, therefore, may only impact on fruit set in cacao trees in direct sunlight, with only minimal to no impact in areas of cacao where natural pollinator activity is high.This research was funded by grants from The American Cocoa Research Institute of the United States of America. I thank T. Noeske for statistical assistance.     

Über die Sekretion saccharosespaltender Transglukosidasen im pflanzlichen Nektar

Summary The phloem sap ofRobinia Pseud-Acacia contains only sucrose and does not possess invertase activity. A sucrase is, however, present in nectar collected fromRobinia flowers: this enzyme identified as a transglucosidase, liberates greater amounts of fructose than of glucose from sucrose. Enzymic activity apparently commences 2–5 days before the flowers are fully open.

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Die vorliegenden Untersuchungen erfolgten im Rahmen der Arbeitsgemeinschaft Prof. Dr.A. Frey-Wyssling, Zürich, und Dr.A. Maurizio, Bern, mit Unterstützung der Fritz-Hoffmann-La-Roche-Stiftung zur Förderung wissenschaftlicher Arbeitsgemeinschaften in der Schweiz.     

Quelques effets de l'acide 2,4-dichlorophénoxyacétique sur les rameaux dePrunus persica (L.) Batsch

Summary 2,4-Dichlorophenoxy acetic acid in lanoline applied on the base of the leaf petiols ofPrunus persica in October causes the deformation of the flowers in April. The ovaries are inexistent and the styles short. The stamens are reduced and curved downwards. The petals are lanceolate, denticulated and of a dark pink colour. The growth substance applied on the bark is transported merely upwards to the top of the branch and little to the base. The starch present in the medullar parts of the xylem disappears completely in the sections bearing deformed flowers. It is suggested that 2,4-dichlorophenoxy acetic acid disturbs the metabolism before having an effect on morphogenesis.     

The association of phytoecdysteroids with flowering in fat hen,Chenopodium album,and other members of the Chenopodiaceae

Very high concentrations of ecdysteroid are associated with flowering inChenopodium album. Highest concentrations are found in anthers, but significant levels are also found in the stamens, carpels and sepals. In contrast, pollen contains only low levels. The ecdysteroid profile is the same in anthers as in whole-plant extracts, with 20-hydroxyecdysone and polypodine B predominating. The results for flowers ofC. album are compared with the patterns determined for other chenopods (C. capitatum, C. polyspermum, C. anthelminticum, C. giganteum, C. quinoa andC. foliosum). The significance of these findings for plant-insect interactions and the relationship to the mode of plant pollination are discussed.     

Pollen carryover and neighbourhood inRanunculus bulbosus

The pattern of gene flow has a major influence on the spatial scale of evolutionary processes. In plant populations pollen carryover will influence the pattern of gene flow. InRanunculus bulbosus L. pollen carryover was found to occur over a maximum of 5 flowers, with seed set per flower decreasing in a curvilinear fashion with increasing visit number in a sequence of visits by a bee after pollen pick-up from a donor plant. The effect of pollen carryover is to increase both neighbourhood area and neighbourhood size by two-fold.     

Occurrence of heavy metal binding phytochelatins in plants growing in a mining refuse area

Summary Phytochelatins were identified in roots of heavy metal-sensitiveAcer pseudoplatanus and-resistantSilene cucubalus plants grown in zinc-rich soil of a mine dump. Both plants, when collected from a metal-uncontaminated stand, located nearby, revealed no phytochelatins. Thus, we concluded that metal-binding phytochelatins are specifically induced in plants of heavy metal enriched ecosystems.     

Fungitoxic properties of Rosa chinensis Jacq

Summary During a systematic survey of higher plants for their fungitoxicity, the flowers of Rosa chinensis Jacq. were found to exhibit strong antifungal properties. On chemical investigation the antifungal principle was isolated as a shining, needle-shaped crystalline substance. It was identified as gallic acid. It exhibited fungistatic action against as many as 17 fungi at 3% concentration.Authors are thankful to Prof. K. S. Bhargava for laboratory facilities.     

Über die Oxydation ungesättigter Fettsäuren durch Pflanzensäfte

Summary Extracts from various parts, including root nodules, of different leguminous plants, and extracts from leaves of several other plants (belonging toSolanaceae andLabiatae) are able to accelerate efficiently the oxidation of unsaturated fatty acids.     

Effects of feeding on healthy and diseased corn plants on a vector and on a non-vector insect

Insect-transmitted plant pathogens can have positive, negative or no effects on the vector insect. Effects could be direct (caused by the pathogen) or indirect (mediated by changes in the plant). Pathogen effects on non-vector insects are less well known.Peregrinus maidis (Ashmead) (Homoptera: Delphacidae), an insect that is not a vector of the corn stunt spiroplasma (CSS), weighed less 15 days after feeding on CSS-infected corn plants relative to insects feeding on healthy corn plants. Fecundity of non-vector insects that were removed from diseased plants was higher than for insects coming from healthy plants. ForDalbulus maidis (DeLong & Wolcott) (Homoptera: Cicadellidae), an insect that transmits CSS, there were no differences in weight, longevity, eggs per day, weekly or total fecundity after feeding on healthy or on CSS-infected corn plants. Significant differences in some phloem amino acids were detected between healthy and CSS-infected plants. Infected plants also showed an increased phloem acidity as disease symptoms progressed. Feeding on CSS-infected corn plants by an insect that does not vector the pathogen infecting the plant can have favorable consequences as evidenced by an increased fecundity.Scientific aritcle no. 8819, contribution no. A-6605 of the Maryland Agricultural Experiment Station.     

The influence of different host plants on some biological aspects ofHeliothis armigera (Hub.)

Summary The suitability of 6 different plants as natural food forHeliothis armigera was tested. The different biological aspects ofH. armigera were taken in consideration. Kidney bean pods and cotton plant leaves were the most successful host plants tested as they increased the pupal weight and the reproductive potential of the resulting moths, followed by lettuce, which decreased the larval duration remarkably.     

Einfluss der Wurzeln auf die Trigonellinsynthese beiCoffea arabica

Summary Young plants ofCoffea arabica were fed 200 µC C¹⁴O₂ each, the carbon dioxide being absorbed by photosynthesis. The specific activity of the alkaloid trigonelline contained in the leaves was shown to be strongly dependent of leaf age. Excised plants without root system or plants with an interrupted shoot-root connection as regards pholem transport (by girdling the stem below the cotyledons) incorporate more radioactive carbon into the molecule of trigonelline than intact plants.     

White leaf disease ofCynodon dactylon Pers., a mycoplasmal disease in India

Summary White leaf disease of Bermuda grass (Cynodon dactylon Pers.) has been reported from a few countries to be caused by a mycoplasma-like organism. We have tried to observe the causal agent in white leaf diseased plants ofC. dactylon collected near Varanasi. Both tetracycline treatment and electron microscopy have revealed the presence of mycoplasma-like bodies in phloem cells of the diseased plants.     

Phytoalexin response is elicited by a pathogen (Rhizoctonia solani) but not by a mycorrhizal fungus (Glomus mosseae) in soybean roots

Summary A container system was constructed to study the response of soybean roots to infection by mycorrhizal or pathogenic fungi. The system allows a rapid and synchronous inoculation byGlomus mosseae orRhizoctonia solani. The phytoalexin glyceollin was measured in roots of inoculated and uninoculated plants for a period of 30 days. A significantly increased content of phytoalexin was found inR. solani-infected roots as compared to uninfected control roots. However, there was no difference in the glyceollin contents of the mycorrhizal and the control roots for up to 23 days after inoculation. The accumulation of glyceollin inR. solani-infected roots was not influenced by a subsequent inoculation withG. mosseae. Moreover glyceollin accumulated in mycorrhizal plants to the same extent as in control plants when they were inoculated withR. solani. The two fungi did not mutually influence the course of infection when they were inoculated together.     

Toxic substances produced byFusarium. III. Production and screening of phytotoxic substances ofF. oxysporum f. sp.carthami responsible for the wilt disease of safflowerCarthamus tinctorius Linn.

Summary Fusarium oxysporum f. sp.carthami, a causative agent for the wilt disease of safflower (Carthamus tinctorius Linn.), has been shown to produce diacetoxyscirpenol, T-2 toxin, fusaric acid and lycomarasmin in artificial media. These substances produced disease syndromes, similar to those seen after the natural infection, when administered in healthy plants. Diacetoxyscirpenol and T-2 toxin have been detected in diseased safflower plants after inoculating with the wilt pathogen. This study is the first demonstration of vivotoxicity of diacetoxyscirpenol.