Betaine accumulation and (/sup 14/C)formate metabolism in water-stressed barley leaves

Conference · Sun Jan 01 04:00:00 EST 1978 · Plant Physiol.; (United States)

OSTI ID:6504831

Hanson, A D; Nelsen, C E

Barley (Hordeum vulgare L.) plants at the three-leaf stage were water-stressed by flooding the rooting medium with polyethylene glycol 6000 with an osmotic potential of -19 bars, or by withholding water. While leaf water potential fell and leaf kill progressed, the betaine (trimethylglycine) content of the second leaf blade rose from about 0.4 micromole to about 1.5 micromoles in 4 days. The time course of betaine accumulation resembled that of proline. Choline levels in unstressed second leaf blades were low (<0.1 micromole per blade) and remained low during water stress. Upon relief of stress, betaine-like proline-remained at a high concentration in drought-killed leaf zones, but betaine did not disappear as rapidly as proline during recovery. When (methyl-/sup 14/C)choline was applied to second leaf blades of intact plants in the growth chamber, water-stressed plants metabolized 5 to 10 times more /sup 14/C label to betaine than control plants during 22 hours. When infiltrated with tracer quantities of (/sup 14/C)formate and incubated for various times in darkness or light, segments cut from water-stressed leaf blades incorporated about 2- to 10-fold more /sup 14/C into betaine than did segments from unstressed leaves. In segments from stressed leaves incubated with (/sup 14/C)formate for about 18 hours in darkness, betaine was always the principal /sup 14/C-labeled soluble metabolite. This /sup 14/C label was located exclusively in the N-methyl groups of betaine; thus, reducing equivalents were available in stressed leaves for the reductive steps of methyl group biosynthesis from formate. Incorporation of /sup 14/C from formate into choline was also increased in stressed leaf tissue, but choline was not a major product formed from (/sup 14/C)formate. These results are consistent with a net de novo synthesis of betaine from 1- and 2-carbon precursors during water stress and indicate that the betaine so accumulated may be a metabolically inert end product.

• Research Organization: Michigan State Univ., East Lansing
• OSTI ID: 6504831
• Conference Information: Journal Name: Plant Physiol.; (United States) Journal Volume: 62
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
550500* -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
ALCOHOLS
AMINES
AMINO ACIDS
AMMONIUM COMPOUNDS
AZOLES
BARLEY
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETAINE
BIOLOGICAL ACCUMULATION
BIOLOGICAL EFFECTS
BIOLOGICAL STRESS
CARBON 14
CARBON ISOTOPES
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CEREALS
CHOLINE
DRUGS
EVEN-EVEN NUCLEI
FORMATES
GRAMINEAE
GRASS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPES
LEAVES
LIGHT NUCLEI
LIPOTROPIC FACTORS
METABOLISM
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PLANTS
PROLINE
PYRROLES
PYRROLIDINES
QUATERNARY COMPOUNDS
RADIOISOTOPES
WATER
YEARS LIVING RADIOISOTOPES