Measurement of xylem sap amino acid concentrations in conjunction with whole tree transpiration estimates spring N remobilization by cherry (Prunus avium L.) trees

Abstract

Prunus avium trees were grown in sand culture for one vegetative season with contrasting N supplies, in order to precondition their N storage capacities. During the spring of the second year a constant amount of 15 N was supplied to all the trees, and the recovery of unlabelled N in the new biomass production was used as a direct measure of N remobilization. Destructive harvests were taken during spring to determine the pattern of N remobilization and uptake. Measurements of both xylem sap amino acid profiles and whole tree transpiration rates were taken, to determine whether specific amino acids are translocated as a consequence of N remobilization and if remobilization can be quantified by calculating the flux of these amino acids in the xylem. Whereas remobilization started immediately after bud burst, N derived from uptake by root appeared in the leaves only 3 weeks later. The tree internal N status affected both the amount of N remobilization and its dynamics. The concentration of xylem sap amino acids peaked shortly after bud burst, concurrently with the period of fastest remobilization. Few amino acids and amides (Gln, Asn and Asp) were responsible for most of N translocated through the xylem; however, their relative concentration varied over spring, demonstrating that the transport of remobilized N occurred mainly with Gln whereas transport of N taken up from roots occurred mainly with Asn. Coupling measurements of amino acid N in the xylem sap with transpiration values was well correlated with the recovery of unlabelled N in the new biomass production. These results are discussed in relation to the possibility of measuring the spring remobilization of N in field-grown trees by calculating the flux of N translocation in the xylem.

Improvement of Fitness and Efficacy of a Fire Blight Biocontrol Agent via Nutritional Enhancement Combined with Osmoadaptation

“…Under high-RH conditions, STA EPS62e cells (see Materials and Methods) maintained initial population levels or slightly increased on flowers, around 10 8 CFU flower Ϫ1 , in Passe Crassane and Abate Fetel pear flowers (Fig. 2).…”

Free amino acids in the xylem sap of pear trees during dormancy

“…(MALAGUTI et al, 2001) and cherry trees (Prunus avium L.) (MILLARD et al, 2006;GRASSI et al, 2002), reaching maximum values near the budding stage. MALAGUTI et al (2001) reported that, 106 days prior to budding, the concentrations of Asn, Asp, and Gln were 287, 109, and 101μg ml -1 sap, respectively.…”

“…In this manner, the initial growth of buds becomes almost entirely dependent on the N reserves of vegetative tissues, since the root system is only activated after the initiation of growth by new sprouts. Although few studies have described the dynamics of the process in detail, it is evident that the remobilization of N occurs before absorption by roots, at least in some species, such as apple (DONG et al, 2001), pear (QUARTIERI et al, 2002), peach (RUFAT & DeJONG, 2001) and cherry trees (GRASSI et al, 2002). One plausible explanation for the remobilization of N from vegetative parts before absorption from soil is the fact that air temperature increases more quickly than soil temperature at the beginning of spring, when rates of N mineralization and availability are still very low (MILLARD & GRELET, 2010).…”

DISTRIBUTION AND RECYCLING OF CANOPY NITROGEN STORAGE RESERVES IN SWEET CHERRY (Prunus avium) FRUITING BRANCHES FOLLOWING 15N-UREA FOLIAR APPLICATIONS AFTER HARVEST

“…Information on the effectiveness of foliar N applications in sweet cherry is lacking. To study the canopy distribution of N applied as urea foliar sprays, an experiment using a "Bing"/"Gisela root absorption begins three weeks later, indicating a dependence on the N reserves early in the season (Grassi et al, 2002;Grassi et al, 2003;Ouzounis and Lang, 2011). N storage reserves represent approximately 50% of the N used for new growth during early spring.…”

“…N storage reserves represent approximately 50% of the N used for new growth during early spring. The remaining N comes from root absorption and soil uptake (Grassi et al, 2002;Grassi et al, 2003;Azarenko and Chozinski, 2005).…”