Xylem sap composition was examined in nodulated and nonnodulated cowpea (Vigna unguiculata [L.] Walp.) plants receiving a range of levels of NO(3) and in eight other ureide-forming legumes utilizing NO(3) or N(2) as sole source of nitrogen. A (15)N dilution technique determined the proportions of plant nitrogen derived from N(2) in the nodulated cowpeas fed NO(3). Xylem sap composition of NO(3)...

Evolutionary, as well as genetic, evidence suggests that vascular development evolved originally as a cell death programme that allowed enhanced movement of water in the extinct protracheophytes, and that secondary wall formation in the water-conducting cells evolved afterwards, providing mechanical support for effective long-distance transport of water. The extant vascular plants possess a com...

BACKGROUND AND AIMS Bacterial leaf scorch occurring in a number of economically important plants is caused by the xylem-limited bacterium Xylella fastidiosa (Xf). In grapevine, Xf systemic infection causes Pierce's disease and is lethal. Traditional dogma is that Xf movement between vessels requires the digestion of inter-vessel pit membranes. However, Yersinia enterocolitica (Ye) (a bacterium ...

The principal forms of amino nitrogen transported in xylem were studied in nodulated and non-nodulated peanut (Arachis hypogaea L.). In symbiotic plants, asparagine and the nonprotein amino acid, 4-methyleneglutamine, were identified as the major components of xylem exudate collected from root systems decapitated below the lowest nodule or above the nodulated zone. Sap bleeding from detached no...

Xylem pressure and its relative response to the imposition of an external osmotic stress (the so-called radial reflection coefficient) were recorded in roots of intact maize plants using the xylem pressure probe technique. Consecutive insertion of two probes into the same xylem vessel or into adjacent vessels of intact roots of plants exposed to high light intensity and salt stress under labora...

Fusarium oxysporum f.sp. conlutinans (Foc) is a serious root-invading and xylem-colonizing fungus that causes yellowing in Brassica oleracea. To comprehensively understand the interaction between F. oxysporum and B. oleracea, composition of the xylem sap proteome of the non-infected and Foc-infected plants was investigated in both resistant and susceptible cultivars using liquid chromatography-...

Due to high directionality and small wavelengths, 60 GHz links are highly vulnerable to human blockage. To overcome blockage, 60 GHz radios can use a phased-array antenna to search for and switch to unblocked beam directions. However, these techniques are reactive, and only trigger after the blockage has occurred, and hence, they take time to recover the link. In this paper, we propose BeamSpy,...

Xylella fastidiosa (Xf) is the causal agent of Pierce’s disease in grapevines. The mechanisms of pathogenicity are largely due to occlusion of xylem vessels by aggregation of Xf and biofilm formation. Our previous work has documented the effects of xylem constituents on both Xf proliferation and biofilm formation. This current research utilizes 1) addition of xylem constituents to defined media...

Plant pathogens secrete small proteins, of which some are effectors that promote infection. During colonization of the tomato xylem vessels the fungus Fusarium oxysporum f.sp. lycopersici (Fol) secretes small proteins that are referred to as SIX (Secreted In Xylem) proteins. Of these, Six1 (Avr3), Six3 (Avr2), Six5, and Six6 are required for full virulence, denoting them as effectors. To invest...

Fungal wilt diseases are a threat to global food safety. Previous studies in perennial crops showed that xylem vessel diameter affects disease susceptibility. We tested the hypothesis that xylem vessel diameter impacts occlusion processes and pathogen compartmentalization in Vitis vinifera L. We studied the interaction between four grape commercial cultivars with the vascular wilt pathogen Phae...