Source-sink relationship in Hausa potato

Fresh tuber yield of Hausa potato [Solenostemon rotundifolius (Poir) J.K. Morton] is generally low in Nigeria, perhaps, due to a lack of balance between the source and the sink. The objective of this study was to investigate the relationship between source-potential and sink-capacity, and its effect on dry matter production and distribution, as well as on dry tuberous yield in reciprocal grafts of four accessions of Hausa potato. Four accessions of Hausa potato were used for reciprocal grafting. The degree of response of source to sink and of sink to source was determined using regression coefficient analysis. The number of tubers per plant, length and girth of tubers varied with accession, source-potential and sink-capacity. The highest source-potential was observed in accession Manchok 2. The highest sink-capacity was observed in accession Langtang. Although accession Manchok 2 had the largest source-potential with respect to dry tuber yield, the highest response of source to sink was observed in accession Bokkos 2, with regression coefficient of 0.83. Accession Langtang had the highest sink-capacity, but the degree of response of sink to source was highest in accession Bokkos 2 with regression coefficient of 3.26. The results showed that the photosynthetic capacity of accessions with large source-potentials is unlikely to be altered by change in sink-capacity. Productivity in Hausa potato may be influenced by the photosynthetic activity of the leaf canopy (source), the capacity of the plant to translocate photo-assimilates to the tuberous root (sink) and the capacity of the tuberous root to accommodate or capture the assimilates

The effects of rising atmospheric carbon dioxide on shoot-root nitrogen and water signaling.

Terrestrial higher plants are composed of roots and shoots, distinct organs that conduct complementary functions in dissimilar environments. For example, roots are responsible for acquiring water and nutrients such as inorganic nitrogen from the soil, yet shoots consume the majority of these resources. The success of such a relationship depends on excellent root-shoot communications. Increased net photosynthesis and decreased shoot nitrogen and water use at elevated CO2 fundamentally alter these source-sink relations. Lower than predicted productivity gains at elevated CO2 under nitrogen or water stress may indicate shoot-root signaling lacks plasticity to respond to rising atmospheric CO2 concentrations. The following presents recent research results on shoot-root nitrogen and water signaling, emphasizing the influence that rising atmospheric carbon dioxide levels are having on these source-sink interactions

Source-sink Relationship During Papaya Fruit Development and Ripening

The source sink relationship during papaya fruit development and ripening was investigated. The source size and sink strength were modified by single or continual defoliation, and fruit thinning, respectively. The relationship between fruit growth, respiration, sugar accumulation and the activity of sucrose phosphate synthase (SPS), sucrose synthase (SS), and acid invertase were determined in fruit from 14 days after anthesis (DAA) to 140 DAA (harvest maturity) and in response to defoliation and fruit removal. A putative complete invertase gene and a SS gene fragment were isolated and characterized from nearly mature green papaya fruit. Single defoliation significantly reduced new flower and fruit set, and ripe fruit total soluble solids (TSS) but did not reduce fruit production, average fruit mass, percentage fruit flesh and seed, seed mass ratio and seed dry mass during a six weeks period. Continual defoliation in addition reduced fruit size, sugar and invertase enzyme activity and fruit production. The responses of defoliation and fruit thinning varied between different cultivars, weather conditions, defoliation time, degree and method. The pattern of gene expression during fruit development was compared with invertase extracted enzyme activity in the presence and absence of sodium chloride (NaCI) and by western blot analysis. The papaya invertase sequence had an open reading frame that encoded a polypeptide chain of 582 residues and calculated molecular weight of 65, 684 Da. The protein was highly homologous to known plant cell wall invertase and 67% identical at the amino acid level to carrot cell wall invertase. The cloned 720 bp SS fragment was highly homologous to A. glutinosa (X92378) and SS genes from other species. Invertase gene was expressed at a higher level during late fruit development stage than in young fruit and other tissues of papaya plant. SS gene expression was higher in young fruit and petiole tissues than in other tissues. The data demonstrated that SS enzyme was a major enzyme in fruit sink establishment and maintenance. Apoplastic invertase had an important function in phloem unloading during papaya fruit sugar accumulation and the activity was regulated at both transcriptional and translational levels

Gene regulatory networks elucidating huanglongbing disease mechanisms.

Next-generation sequencing was exploited to gain deeper insight into the response to infection by Candidatus liberibacter asiaticus (CaLas), especially the immune disregulation and metabolic dysfunction caused by source-sink disruption. Previous fruit transcriptome data were compared with additional RNA-Seq data in three tissues: immature fruit, and young and mature leaves. Four categories of orchard trees were studied: symptomatic, asymptomatic, apparently healthy, and healthy. Principal component analysis found distinct expression patterns between immature and mature fruits and leaf samples for all four categories of trees. A predicted protein - protein interaction network identified HLB-regulated genes for sugar transporters playing key roles in the overall plant responses. Gene set and pathway enrichment analyses highlight the role of sucrose and starch metabolism in disease symptom development in all tissues. HLB-regulated genes (glucose-phosphate-transporter, invertase, starch-related genes) would likely determine the source-sink relationship disruption. In infected leaves, transcriptomic changes were observed for light reactions genes (downregulation), sucrose metabolism (upregulation), and starch biosynthesis (upregulation). In parallel, symptomatic fruits over-expressed genes involved in photosynthesis, sucrose and raffinose metabolism, and downregulated starch biosynthesis. We visualized gene networks between tissues inducing a source-sink shift. CaLas alters the hormone crosstalk, resulting in weak and ineffective tissue-specific plant immune responses necessary for bacterial clearance. Accordingly, expression of WRKYs (including WRKY70) was higher in fruits than in leaves. Systemic acquired responses were inadequately activated in young leaves, generally considered the sites where most new infections occur

Trace gas mixing ratio variability versus lifetime in the troposphere and stratosphere: Observations

Several archived data sets have been reviewed to examine the relationship between mixing ratio variability and lifetime for hydrocarbon and halocarbon species in the troposphere and stratosphere. The dependence on lifetime was described by the power law relationship slnX = Aτ-b, where slnX is the standard deviation of the In of the mixing ratios, A is a proportionality coefficient, and b is an exponent that relates to the dominance of sink terms in the regional variability budget. At the Harvard forest ground site, winter and summer data displayed the same lifetime dependence, τ-0.18, which was significantly weaker than the τ-0.5 dependence of remote tropospheric data, indicating that source terms dominated regional variability at Harvard. In addition, the ratio of summer to winter slnX values was found to be similar for all species except ethane, averaging 1.54 ± 0.04. This ratio is consistent with a factor of 11 seasonal change in the species lifetimes, given a τ-0.18 lifetime dependence. Stratospheric data displayed a stronger lifetime dependence than tropospheric trends, indicating a more dominant role for sink terms in describing spatial variability in this region of the atmosphere. We show that a unique power law relationship between slnX ratios for two species Xi and Xj and the kinetic slope of ln(Xi) versus ln(Xj) correlation plots is found to hold in both observations and theory. Thus knowledge of the coefficient b allows for a clearer understanding of the relationship between observed slopes of ln(Xi) versus ln(Xj) correlation plots and the ratio of the species lifetimes. Copyright 1999 by the American Geophysical Union

The Least-core and Nucleolus of Path Cooperative Games

Cooperative games provide an appropriate framework for fair and stable profit distribution in multiagent systems. In this paper, we study the algorithmic issues on path cooperative games that arise from the situations where some commodity flows through a network. In these games, a coalition of edges or vertices is successful if it enables a path from the source to the sink in the network, and lose otherwise. Based on dual theory of linear programming and the relationship with flow games, we provide the characterizations on the CS-core, least-core and nucleolus of path cooperative games. Furthermore, we show that the least-core and nucleolus are polynomially solvable for path cooperative games defined on both directed and undirected network

The complexity of sediment recycling as revealed by common Pb isotopes in K-feldspar

© 2018 China University of Geosciences (Beijing) and Peking University. Detrital zircon U–Pb geochronology has become the gold standard in evaluating source to sink relationships in sedimentary basins. However, the physical and chemical robustness of zircon, which make it such a useful mineral for provenance studies, is also a hindrance as zircon can be recycled through numerous sedimentary basins, thus obscuring the first cycle source to sink relationship. An elegant approach to addressing this potential issue is to compare the Pb isotope composition of detrital K-feldspar, a mineral which is unlikely to survive more than one erosion-transport-deposition cycle, with that of magmatic K-feldspar from potential basement source terranes. Here we present new in situ Pb isotope data on detrital K-feldspar from two Proterozoic arkosic sandstones from Western Australia, and magmatic K-feldspar grains from potential igneous source rocks, as inferred by the age and Hf isotope composition of detrital zircon grains. The data indicate that the detrital zircon and K-feldspar grains could not have been liberated from the same source rocks, and that the zircon has most likely been recycled through older sedimentary basins. These results provide a more complete understanding of apparently simple source to sink relationships in this part of Proterozoic Western Australia