Metabolic profiles of six African cultivars of cassava (Manihot esculenta Crantz) highlight bottlenecks of root yield

Open Access Article; Published online: 17 Jan 2020Cassava is an important staple crop in sub‐Saharan Africa, due to its high productivity even on nutrient poor soils. The metabolic characteristics underlying this high productivity are poorly understood including the mode of photosynthesis, reasons for the high rate of photosynthesis, the extent of source/sink limitation, the impact of environment, and the extent of variation between cultivars. Six commercial African cassava cultivars were grown in a greenhouse in Erlangen, Germany, and in the field in Ibadan, Nigeria. Source leaves, sink leaves, stems and storage roots were harvested during storage root bulking and analyzed for sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, protein, activities of enzymes in central metabolism and yield traits. High ratios of RuBisCO:phosphoenolpyruvate carboxylase activity support a C3 mode of photosynthesis. The high rate of photosynthesis is likely to be attributed to high activities of enzymes in the Calvin–Benson cycle and pathways for sucrose and starch synthesis. Nevertheless, source limitation is indicated because root yield traits correlated with metabolic traits in leaves rather than in the stem or storage roots. This situation was especially so in greenhouse‐grown plants, where irradiance will have been low. In the field, plants produced more storage roots. This was associated with higher AGPase activity and lower sucrose in the roots, indicating that feedforward loops enhanced sink capacity in the high light and low nitrogen environment in the field. Overall, these results indicated that carbon assimilation rate, the K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation are potential target traits for genetic improvement

Status Updates Over Unreliable Multiaccess Channels

Applications like environmental sensing, and health and activity sensing, are supported by networks of devices (nodes) that send periodic packet transmissions over the wireless channel to a sink node. We look at simple abstractions that capture the following commonalities of such networks (a) the nodes send periodically sensed information that is temporal and must be delivered in a timely manner, (b) they share a multiple access channel and (c) channels between the nodes and the sink are unreliable (packets may be received in error) and differ in quality. We consider scheduled access and slotted ALOHA-like random access. Under scheduled access, nodes take turns and get feedback on whether a transmitted packet was received successfully by the sink. During its turn, a node may transmit more than once to counter channel uncertainty. For slotted ALOHA-like access, each node attempts transmission in every slot with a certain probability. For these access mechanisms we derive the age of information (AoI), which is a timeliness metric, and arrive at conditions that optimize AoI at the sink. We also analyze the case of symmetric updating, in which updates from different nodes must have the same AoI. We show that ALOHA-like access, while simple, leads to AoI that is worse by a factor of about 2e, in comparison to scheduled access

A subsynoptic-scale kinetic energy study of the Red River Valley tornado outbreak (AVE-SESAME 1)

The subsynoptis-scale kinetic energy balance during the Red River Valley tornado outbreak is presented in order to diagnose storm environment interactions. Area-time averaged energetics indicate that horizontal flux convergence provides the major energy source to the region, while cross contour flow provides the greatest sink. Maximum energy variability is found in the upper levels in association with jet stream activity. Area averaged energetics at individual observation times show that the energy balance near times of maximum storm activity differs considerably from that of the remaining periods. The local kinetic energy balance over Oklahoma during the formation of a limited jet streak receives special attention. Cross contour production of energy is the dominant local source for jet development. Intense convection producing the Red River Valley tornadoes may have contributed to this local development by modifying the surrounding environment

Effect of changed source/sink relations on proteolytic activities and on nitrogen mobilization in field-grown wheat (Triticum aestivum L.)

Nitrogen mobilization and the pattern of proteolytic enzymes were investigated in leaves and glumes of field-grown winter wheat (Triticum aestivum L.) during maturation. Source/sink relations were changed by removal of the ear, the flag leaf or the lower leaves shortly after anthesis. Removal of the ear was most effective, resulting in delayed senescence of the flag leaf with the chlorophyll, aminopeptidase and carboxypeptidase activities remaining high in contrast to the control, whereas neutral endopeptidase activity increased more slowly. No major changes were observed in the second leaf from the top in plants with either ears or flag leaves removed. Nitrogen mobilization and proteolytic activities in glumes and the remaining leaves were influenced only slightly by leaf removal. In earless plants, nitrogen was transported from the second leaf into the leaf sheath and stem, but in the flag leaf the total reduced nitrogen remained high and free amino groups increased. The increase in endopeptidase activity was influenced by the source/sink relations. However, the accumulation of amino groups and the increasing endopeptidase activity in the flag leaf of earless plants suggest that the nitrogen sink capacity did not greatly control protein degradation; it remains to be seen whether phytohormones, accumulated amino acids or other factors delayed the increase in endopeptidase activit

RTXP : A Localized Real-Time Mac-Routing Protocol for Wireless Sensor Networks

Protocols developed during the last years for Wireless Sensor Networks (WSNs) are mainly focused on energy efficiency and autonomous mechanisms (e.g. self-organization, self-configuration, etc). Nevertheless, with new WSN applications, appear new QoS requirements such as time constraints. Real-time applications require the packets to be delivered before a known time bound which depends on the application requirements. We particularly focus on applications which consist in alarms sent to the sink node. We propose Real-Time X-layer Protocol (RTXP), a real-time communication protocol. To the best of our knowledge, RTXP is the first MAC and routing real-time communication protocol that is not centralized, but instead relies only on local information. The solution is cross-layer (X-layer) because it allows to control the delays due to MAC and Routing layers interactions. RTXP uses a suited hop-count-based Virtual Coordinate System which allows deterministic medium access and forwarder selection. In this paper we describe the protocol mechanisms. We give theoretical bound on the end-to-end delay and the capacity of the protocol. Intensive simulation results confirm the theoretical predictions and allow to compare with a real-time centralized solution. RTXP is also simulated under harsh radio channel, in this case the radio link introduces probabilistic behavior. Nevertheless, we show that RTXP it performs better than a non-deterministic solution. It thus advocates for the usefulness of designing real-time (deterministic) protocols even for highly unreliable networks such as WSNs

#mytweet via Instagram: Exploring User Behaviour across Multiple Social Networks

We study how users of multiple online social networks (OSNs) employ and share information by studying a common user pool that use six OSNs - Flickr, Google+, Instagram, Tumblr, Twitter, and YouTube. We analyze the temporal and topical signature of users' sharing behaviour, showing how they exhibit distinct behaviorial patterns on different networks. We also examine cross-sharing (i.e., the act of user broadcasting their activity to multiple OSNs near-simultaneously), a previously-unstudied behaviour and demonstrate how certain OSNs play the roles of originating source and destination sinks.Comment: IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining, 2015. This is the pre-peer reviewed version and the final version is available at http://wing.comp.nus.edu.sg/publications/2015/lim-et-al-15.pd