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Query: UNIPROT:P39060 (
endostatin
)
2,284
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Experiments were designed to study the importance of organic acids as counterions for K(+) translocation in the xylem during excess cation uptake. A comparison was made of xylem exudate from wheat seedlings treated 72 hours with either 1.0 millimolar
KNO
(3) or 0.5 millimolar K(2)SO(4), both in the presence of 0.2 millimolar CaSO(4). Exudation from
KNO
(3) plants had twice the volume and twice the K(+) and Ca(2+) fluxes or rate of delivery to shoots, as K(2)SO(4) plants.
Malate
flux was 25% higher in K(2)SO(4) than in
KNO
(3) exudate.
Malate
was the principal anion accompanying K(+) or Ca(2+) in K(2)SO(4) treatment, while in the
KNO
(3) treatment, NO(3) (-) was the principal anion. The contribution of SO(4) (2-) was negligible in both treatments. In a second experiment, exudate was collected every 4 hours during the daytime throughout a 72-hour treatment with
KNO
(3).
Malate
was the only anion present in exudate at first, just after the CaSO(4) pretreatment had ended.
Malate
concentration decreased and NO(3) (-) concentration increased with time and these concentrations were negatively correlated. By 62 hours, NO(3) (-) represented 80% of exudate anions. K(+) and NO(3) (-) concentrations in exudate were strongly correlated with K(+) and NO(3) (-) uptake, respectively. The first 36 hours of absorption from
KNO
(3) solution resembled the continuous absorption of K(2)SO(4), in that malate was the principal counterion for translocation of K(+).
...
PMID:Organic Acids and Ionic Balance in Xylem Exudate of Wheat during Nitrate or Sulfate Absorption. 1666 Dec 48
Azospirillum sp. B510, a free-living nitrogen-fixing bacterium isolated from the stems of rice (Oryza sativa cv. Nipponbare), was investigated to establish effective conditions for the colonization of rice plants. We analyzed the effects of the nitrogen sources
KNO
3
, NH
4
Cl, urea (CO[NH
2
]
2
), and NH
4
NO
3
at different concentrations (0.01-10 mM) on this colonization. Nitrogen promoted plant growth in a concentration-dependent manner, with minor differences being observed among the different nitrogen sources. Bacterial colonization was markedly suppressed on media containing NH
4
+
concentrations higher than 1 mM. Since concentrations of up to and including 10 mM NH
4
+
did not exhibit any antibacterial activity, we analyzed several factors affecting the NH
4
+
-dependent inhibition of endophytic colonization, including the accumulation of the reactive oxygen species H
2
O
2
and the secretion of the chemotactic substrate
malic acid
. The accumulation of H
2
O
2
was increased in rice roots grown on 1 mM NH
4
Cl. The amounts of
malic acid
secreted from NH
4
-grown rice plants were lower than those secreted from plants grown without nitrogen or with
KNO
3
. Although the bacterium exhibited chemotactic activity, moving towards root exudates from plants grown without nitrogen and
KNO
3
-grown plants, this activity was not observed with root exudates from NH
4
+
-grown plants. NH
4
+
, but not NO
3
-
, caused the acidification of growth media, which inhibited plant bacterial colonization. These NH
4
+
-dependent phenomena were markedly suppressed by the stabilization of medium pH using a buffer. These results demonstrate that the type and concentration of nitrogen fertilizer affects the colonization of rice plants by Azospirillum sp. B510.
...
PMID:Effects of Different Sources of Nitrogen on Endophytic Colonization of Rice Plants by Azospirillum sp. B510. 3015 65
