Physiological Changes in Phaseolus vulgaris in Response to Long-term Ozone Exposure

The effects of ozone on Phaseolus vulgaris cv. Lit were investigatedusing open-top chambers (OTCs) ventilated with charcoal andPurafil filtered air (CF treatments), ambient air (NF treatments)and ambient air to which low, medium or high concentrationsof ozone were added (NFL, NFM and NFH). Ozone additions of 8,16 and 23 nl l^–1 were made during phase 1 of the experiment(0–44 d after emergence, DAE), and additions of 15, 30and 47 nl l^–1 were made during phase 2 (45–99 DAE).Ozone was added to the chambers between 1100 and 1800 h GMT,for 3 or 4 consecutive days each week. The seasonal 7-h meanozone concentrations were 8, 21, 27, 33 and 38 nl l^–1in the CF, NF, NFL, NFM and NFH treatments, respectively. No visible symptoms of ozone injury or significant physiologicalchanges were detected in P. vulgaris during phase I of the experiment.In phase 2, the photosynthesis (Pn) and stomatal conductance(gs) of NFH-plants were inhibited by 73% and 86%, respectively,during ozone exposure, and recovered to pre-exposure valueson the following day. These observations were made prior tothe appearance, 60 DAE, of bronze lesions on the leaves of NFH-plants.The photosynthetic capacity and gs of NFH-leaves decreased asthe severity of ozone injury increased. Rates of weight lossfrom excised leaves also increased with increasing ozone injury.Microscopic investigations of the bronzed regions revealed extensivecellular breakdown, including tonoplast and chloroplast enveloperupture, and the aggregation of the cytoplasmic contents towardsone end of the cell. Severely damaged leaves abscised from the plants, resultingin premature canopy senescence in the NFM and NFH treatments.This, coupled with the lower photosynthetic capacity of existingleaves led to 25 % lower yield in the NFH than the NF treatment(P < 0.05). Phaseolus vulgaris, green bean, ozone, symptom development, photosynthesis, cell ultrastructure     

A glasshouse test to assess the sensitivity of potato cultivars to tobacco rattle virus

The sensitivity to tobacco rattle virus of nine potato cultivars and 24 potato clones from the potato breeding programme at SCRI was assessed in a glasshouse pot test and in field trials for two consecutive years. The results and analyses presented indicate that the pot test gives an accurate and reliable estimate of sensitivity to tobacco rattle virus. Methods of assessing severity of expression of disease symptoms were examined. The advantages of such a glasshouse pot test and its application are discussed.     

Die Eiablagehandlung der Mittelmeerfruchtfliege Ceratitis capitata Wied. Ihre Abhängigkeit von Größe und Dichte der Früchte

• 1 In Zweifachwahlen bevorzugten unbeeinflußte Mittelmeerfruchtfliegen die größere Attrappe für die Eiablage, sofern Größen zwischen 1 cm und 6 cm angeboten wurden. In Einfachwahlen wurden Kugeln von 3 cm und 6 cm φ gleich gut belegt, solche von 1–2 cm φ dagegen gemieden.
• 2 Die Bevorzugung der größeren Attrappe war unabhängig von der Attrappenfarbe und bei 1500 Lux auch von der Licht- oder Schattenlage der Einstichöffnungen.
• 3 Behaarte Oberflächen und klaffende Spalten störten die Legetätigkeit auch an Früchten optimaler Größe. In Einfachwahlen wurde die Eiablage durch stark behaarte Oberflächen aber nicht verhindert, sondern nur verzögert.
• 4 Äpfel von 4–6 cm φ regten gleich stark zum Bohren an, für die Eiablage bevorzugten die ♀ ♀ jedoch die leichter anstechbaren. Äpfel von 2 cm φ wurden immer nur schwach belegt.
• 5 Attrappengruppen wurden Einzelattrappen stets vorgezogen, sofern alle Kugeln gleich groß waren. Dagegen enthielten beide Anordnungen die gleiche Eimenge, wenn nur die Einzelattrappe stark nach Cox Orange duftete. War die Einzelattrappe größer als die Attrappen der Gruppe, wurde die Gruppe vernachlässigt. Die Legeleistung war von der Anzahl der Attrappen unabhängig.
• 6 Der Beginn der Bohrtätigkeit und die Aufenthaltsdauer an den Attrappen waren abhängig von der Oberflächenkrümmung.
• 7 Attrappen von 2–6 cm φ wurden auch in Umwegversuchen recht unterschiedlich belegt. Bezogen auf das jeweilige Volumen enthielten dagegen alle ungefähr die gleiche Eimenge.
• 8 Die Anzahl der Besucher und die relative Flugaktivität waren abhängig von der Größe und Dichte der Früchte oder Attrappen, die Bohr- und Legetätigkeit dagegen nur von der Oberflächenstruktur und -krümmung der einzelnen Körper.
• 9 Die ♀♀ bevorzugten in Zweifachwahlen die größere Attrappe, unabhängig davon, ob sie beide Körper gleichzeitig nebeneinander oder nur zeitlich nacheinander wahrnehmen konnten. Die Größere wurde nicht nur ihrer optischen, sondern auch ihrer taktilen Merkmale wegen stärker belegt.

     

SOME EFFECTS OF FEEDING BY LYGUS VOSSELERI POPP. (HETEROPTERA, MIRIDAE) ON THE STEM APEX OF THE COTTON PLANT

The effects of damage to the main stem apex of the cotton plant caused by feeding of Lygus vosseleri Popp. have been investigated using a cell counting technique. It was found that mechanical damage of the tip due either to feeding of Lygus or to pricking with a glass needle caused an increase in cell division and maturation rates in the stem apex. The significance of this in relation to the possible effects of Lygus damage on plant height is discussed.     

Interspecific Hybridization of Trifolium repens with T. hybridum Using In Ovulo Embryo and Embryo Culture

In ovulo embryo culture followed by culture of excised immatureembryos produced interspecific hybrids between Trifolium repensL. (white clover) and autotetraploid T. hybridum L. (alsikeclover). Ovules containing hybrid embryos were excised 12–14 dafter pollination and cultured on Nitsch (1951) medium supplementedwith 15% young cucumber juice for 5–6 d. Embryos weresubsequently excised and transferred to hormone-free EG medium,a medium suitable for the culture of immature embryos. A total of 118 hybrid seedlings were obtained from 1978 reciprocalpollinations. All seedlings produced showed various chlorophylldeficiencies, either totally albino or albino with green sectors.Transmission electron microscope studies were carried out toinvestigate plastid development in embryos and seedlings. Someembryos produced only callus. Plants were regenerated from sevencalli. Two semi-albino plants survived transfer to soil, andone plant produced flowers. Backcrosses to T. repens producedone green plant. Hybridity is supported by analysis of morphological characters,karyotype and the gel electrophoretic separation of leaf isozymes. Pollen irradiated with 40 Gy of gamma rays was also used forpollinations. Results indicate that in certain cases ionizingradiation might be useful in overcoming hybrid inviability. Trifolium repens, Trifolium hybridum, clover, interspecific hybridization, in ovulo embryo culture, irradiation     

The elimination of clover diseases by shoot tip culture

Shoot tip culture was used to eliminate white clover mosaic virus (WCMV) and red clover necrotic mosaic virus (RCNMV) from red clover, and clover phyllody disease (CP) and clover red leaf disease (CRL) from white clover. Shoot tips up to 2.4 mm (in some cases 3 mm) could regenerate plants free from the pathogens, but the efficiency of elimination, at least for WCMV and CRL, tended to decrease with increasing shoot tip size. The efficiency of plant regeneration from shoot tips generally improved with increasing tip size.     

Growth-Regulating Substances and the Growth of Tiller Buds in Barley; Effects of Cytokinins

An hypothesis was set up from which it was predicted that applicationof cytokinin to barley seedlings grown without mineral nutrientswould lead to rapid growth of the coleoptile and first leaftiller buds. Application of cytokinins to the leaves was ineffective,but supplying a number of known cytokinins by steeping the rootsof 4 d old seedlings in solution for 4 h led to significantgrowth of the coleoptile bud. Adenine and cytokinin analogueshad no effect. Supplying cytokinins through the roots also furtherenhanced the growth of buds of plants given mineral nutrients.Cytokinin treatment reduced root dry matter, with small reductionsin mean axis length and number of lateral roots. For plantsnot given mineral nutrients reduction in root weight was compensatedby an increase in weight of the aerial parts; however, for plantssupplied with mineral nutrients this was not so and the lowerroot weight resulted in a smaller total plant dry weight. An interpretation of tiller bud growth in terms of control byinteracting effects of mineral nutrition, assimilate supply,and cytokinin availability is proposed.