Table II.

Effects of low Man and high phosphate supply on respiration rate and Pi, ester-phosphates, sugars, and amino acid contents in maize root tips

Metabolites	δ	Control	Starvation	Glc 2 mm Pi 30 mm	Man 2 mm Pi 30 mm
Respiration	nmol tip−1 min−1	3.27	1.17	2.45	1.34
31P-NMR
	δ ppm	nmol tip−1
Pi	2.3	15.7	41	260	170
G6P	4.36 and 4.32	5.2	1.1	1.4	1.1
M6P	4.28	0.45	0.15	0.35	6.8
M1P	1.86	<0.02	<0.02	<0.02	1.9
P-Eth	3.8	<1.00	4.0	1.8	1.7
P-Chol	3.3	1.75	7.85	6.9	6.9
PEP	−0.66	0.13	0.13	0.15	0.02
UDPG	−12.56 and −12.69	1.67	0.72	0.52	0.34
UDPM	−13.58 and −13.70	<0.02	<0.02	<0.02	0.38
13C-NMR
Suc	104.40	93	<1	<1	29
Glc	96.70	74	<1	7.5	7.5
Man	95.04	<1	<1	<1	12.5
Asp	35.60	3	175	190	120

Excised root tips (1,900) were incubated either for 4 h in a medium containing 200 mm Glc (control), or for 48 h in a medium containing no carbon substrate (starvation), 2 mm Glc/30 mm Pi, or 2 mm Man/30 mm Pi. Tissue extracts, prepared as described in “Materials and Methods,” were analyzed at 21°C with a Bruker AMX 400 WB spectrometer. A concentric capillary containing 13.75 mm TMSP and 0.975 mm methyl diphosphonate in water provided an external reference for ¹³C and ³¹P chemical shifts and also intensities, respectively. The molecular concentrations were determined from the resonance intensities of the relaxed spectra taken as peak areas. Peaks of interest and references were integrated and the calibrate reference allowed direct calculation of the molecular concentrations in the extract, and then within one root tip. Pi, Inorganic phosphate; G6P, Glc-6-P; M6P, Man-6-P; M1P, Man-1-P; P-eth, phosphorylethanolamine; P-chol, phosphorylcholine; PEP, phosphoenolpyruvate; UDPG, UDP-Glc; UDPM, UDP-Man. sd are below 20%.