Allantoin and amino acid composition in xylem exudates of nodulated and nitrate-dependent cowpea plants

Wan Mohamad Wan Othman, . Allantoin and amino acid composition in xylem exudates of nodulated and nitrate-dependent cowpea plants. pp. 53-63. ISSN 0126-6128

The effects of Rhizobium inoculation and exogenus N concentrations 0 0.5 1 2 4.0 and 8.0 mM N as Ca(N)3)2 on plant growth nodulation N2 fixation amino acid composition and ureide abundance in xylem exudates of nodulated cowpea (Vigna unguiculata L. Walp cv. Kausband) were investigated in glasshouse-grown plants in sand culture. Without applied N inoculation markedly increased N2 fixation top growth and allantoin concentration in exudates compared with uninoculated control. Exogenous N applied only to nodulated plants had no beneficial effects on top root or whole plant growth compared with inoculated control but nodule mass and size and N2 fixation decreased substantially with increasing N concentrations exceeding 1.0 mM. However nodule number was unaffected by any N concentration. Allantoin concentration and relative ureide index (ureide N/total N in exudates) x 100 declined drastically with N concentration but the abundance of NO3-N in the exudates followed the reverse trend. In plants fully dependent on Rhizobium symbiosis allantoin was the predominant (94) export product recovered in xylem exudates with the remaining N solutes comprising of NO3-N (4.5) and amino-N (1.5). Conversely N)3-N was the principal (87) form of N exported in xylem of NO3-dependent plants. Although 20 different amino acids were identified in the exudates glutamine was the most abundant component (65) in the nodule-dependent crop whereas asparagine was the predominant (43) amino acid in the NO3-dependent plants. Nodule mass and relative ureide index were highly and positively correlated (r 0.959 ). Allantoin concentration and N2 fixation had low correlation coefficient (r 0.655 ). The significance of these data in biological nitrogen fixation studies is discussed

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Abstract

The effects of Rhizobium inoculation and exogenus N concentrations 0 0.5 1 2 4.0 and 8.0 mM N as Ca(N)3)2 on plant growth nodulation N2 fixation amino acid composition and ureide abundance in xylem exudates of nodulated cowpea (Vigna unguiculata L. Walp cv. Kausband) were investigated in glasshouse-grown plants in sand culture. Without applied N inoculation markedly increased N2 fixation top growth and allantoin concentration in exudates compared with uninoculated control. Exogenous N applied only to nodulated plants had no beneficial effects on top root or whole plant growth compared with inoculated control but nodule mass and size and N2 fixation decreased substantially with increasing N concentrations exceeding 1.0 mM. However nodule number was unaffected by any N concentration. Allantoin concentration and relative ureide index (ureide N/total N in exudates) x 100 declined drastically with N concentration but the abundance of NO3-N in the exudates followed the reverse trend. In plants fully dependent on Rhizobium symbiosis allantoin was the predominant (94) export product recovered in xylem exudates with the remaining N solutes comprising of NO3-N (4.5) and amino-N (1.5). Conversely N)3-N was the principal (87) form of N exported in xylem of NO3-dependent plants. Although 20 different amino acids were identified in the exudates glutamine was the most abundant component (65) in the nodule-dependent crop whereas asparagine was the predominant (43) amino acid in the NO3-dependent plants. Nodule mass and relative ureide index were highly and positively correlated (r 0.959 ). Allantoin concentration and N2 fixation had low correlation coefficient (r 0.655 ). The significance of these data in biological nitrogen fixation studies is discussed

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Item Type:	Article
Additional Information:	Summaries (En Ms)
AGROVOC Term:	VIGNA UNGUICULATA
AGROVOC Term:	INOCULACION
AGROVOC Term:	ALANTOINA
AGROVOC Term:	AMINOACIDOS
AGROVOC Term:	COMPOSICION QUIMICA
AGROVOC Term:	XILEMA
AGROVOC Term:	CAUPI
AGROVOC Term:	RHIZOBIUM
AGROVOC Term:	FIJACION DEL NITROGENO
AGROVOC Term:	NODULACION
Depositing User:	Ms. Norfaezah Khomsan
Last Modified:	24 Apr 2025 05:56
URI:	http://webagris.upm.edu.my/id/eprint/20729

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