New structure in cell puncture activities by aphid stylets: a dual-mode EPG study

Intracellular punctures by aphid stylets appear as potential drop (pd) waveforms in DC electrical penetration graph (EPG) recordings. We used a dual-EPG device that recorded in one channel the ‘full EPG’ with R-plus emf-components (i.e., the usual DC EPG) and concurrently in a second channel the ‘R-EPG’ with R-components only. The circuit of the latter channel was an optimised amplitude modulation (AM) version derived from early (before 1990) AC systems. We also made some ‘emf-EPG’ recordings using a separate high input resistance ‘emf-amplifier’ sensitive to emf-components only. The intracellular pd waveforms have previously been divided into three subphases, and we aimed to distinguish and separate these subphases more accurately by the dual-EPG recordings than with the normal full EPG only. In this study, we temporarily distinguished five subphases (a–e), but unequivocal distinction of only a few of these appeared possible, in spite of the information coming from the two signals. The lack of clearly separable features in R-EPG signals often provided serious difficulties in pd recognition without the concurrent full EPG, but once located, only subphase II-2 features were clear and supported the II-2 data from the full EPG. Consequently, we could not distinguish subphases of complete pd waveforms better with additional R-EPG information during cell punctures by Aphis gossypii Glover (Hemiptera: Aphididae). In Brevicoryne brassicae (L.) (Hemiptera: Aphididae), however, distinguishing II-2 subphases in the full EPG was sometimes a problem. Our detailed dual-EPG observations showed some waveform continuity from halfway into the II-1 subphase (start of the newly recognised subphase ß) until the end of the pd, with a strong but variable emf origin. This waveform tended to overrule other subphase waveforms in B. brassicae more than in A. gossypii and Myzus persicae (Sulzer) (Hemiptera: Aphididae). Subphase waveforms in full EPGs were especially difficult to recognise when pd periods had been interrupted in a virus inoculation experiment and additional R-EPG information could then be useful. This inoculation experiment showed again that only the first subphase (II-1) contributes to virus (Cucumber mosaic virus) inoculation by A. gossypii. In B. brassicae, the benefit of concurrent R-EPG information in such virus experiments is presently under further investigation. Apart from this special application to virus experiments, we do not recommend the routine use of the dual-EPG device. Furthermore, we do not advocate the distinction of more than the previously recognised three intracellular pd subphases as a feasible option in future studies. Analysis of EPGs with concurrent R-EPGs requires substantially more analysis work without yielding consistently useful additional insights. This confirms earlier dual-EPG results from thrip

Tissue location of resistance in apple to the rosy apple aphid established by electrical penetration graphs

A study of the constitutive resistance of the apple cultivar Florina, Malus domestica Borkh. (Rosaceae), to the rosy apple aphid, Dysaphis plantaginea (Passerini) (Homoptera Aphididae), was performed for the first time by the electrical penetration graph (DC-EPG) system, using the susceptible apple cultivar Smoothe as control. All experiments were conducted with apterous adult virginoparae. The results showed a constitutive resistance in Florina due to a much longer period before the first probe reflecting surface factors. Some weak indications were found for pre-phloem resistance and initiating phloem access was not affected as inferred from equal time to show phloem salivation. However, the complete absence of phloem ingestion indicates a major resistance factor in the phloem sieve elements, most likely in the sieve element sap. Surface factors could have affected tissue related variables and this should be studied further. Anyhow, the strong constitutive resistance in Florina, either on the surface alone or in the phloem as well, effectively prevented reliable experiments on induced resistance, previously detected by molecular methods

The strategic function of quality in the management of innovation

Quality management can be used to support strategically the management of innovation. Tools in strategic quality management can be useful in: creating the organizational conditions in which innovations can be developed; supervising and initiating innovation processes; producing innovation content; and implementing innovations in the primary processes of the organization. This conclusion is based on the results of a research project in the Dutch construction industry. In a large-scale house-building project the supportive use of quality tools in the management of innovation was studied. The study indicates that quality tools are used implicitly and sometimes explicitly to manage innovation processes

Planning with water and traffic networks: Carrying structures of the urban landscape

The two networks strategy is a guiding model for planning and design that takes the networks of water and traffic as carrying structures. Its origin is in the early 1990s when it resulted from research by design projects aiming at the generation of tools for making urban development and the urban landscape more ecological. Reviewing practical experiences is one reason to look again at the strategy. A second reason is to explore the possible contribution to current debates such as those about complexity, landscape urbanism and landscape as infrastructure. The origin of the two networks strategy goes back to Ian McHarg’s Design with Nature and Michael Hough’s City Form and Natural Process. Inspired by them, the approach does not, in the first place, take nature and ecology to create limiting but carrying conditions. This asks for carrying structures. In the urban landscape there are at least three crucial fields of synergy between activities that ask for carrying structures: the territorial or spatial field or the area perspective, the activities related to flows that pass through these areas or the flow perspective, and the human activities involved in the plan and in the planning process or the actor perspective. The two networks create conditions for two multi-functional environments of synergy. The fast lane is the competitive profit-oriented zone where efficient production comes first. The traffic network is the carrier. The slow lane is the co-operation based non-profit oriented zone where water safety and quality, landscape and heritage, biodiversity, recreation and local food production are brought together. Here, the water network based on the drainage pattern is the carrier

Stylet Penetration Activities by Aphis craccivora (Homoptera: Aphididae) on Plants and Excised Plant Parts of Resistant and Susceptible Cultivars of Cowpea (Leguminosae)

Direct current electrical penetration graphs (DC-EPGs) were used to analyze the stylet penetration activities of cowpea aphid, Aphis craccivora Koch, on plants of aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultivars of cowpea, Vigna unguiculata (L.) Walpers. Aphid stylet penetration on whole plants at seedling, flowering, and podding stages were studied in one experiment, and in another experiment excised leaves from seedling plants, excised flowers, and excised pods were tested. Electrical signals depicting the aphid stylet penetration activities on their host plants were amplified, recorded onto a paper chart recorder, and scored for specific waveform patterns. Compared with similar tissues of ICV-1, intact leaves and excised seedling foliage of ICV-12 plants caused severe disruption of aphid stylet penetration activities. This was manifested in frequent penetration attempts that were abruptly terminated or unsustained, and in shorter penetration times, signifying antixenosis resistance in ICV-12. There was reduced occurrence of E waveforms, which represent stylet activity in plant vascular tissues. Also, prior exposure of test aphids to plants of one cultivar did not significantly influence the expected stylet penetration activities on plants of the other cultivar. Overall, ICV-12 exhibited high levels of resistance against A. craccivor