Agriculture Reference
In-Depth Information
Chapter 12
S
TABILIZING
P
RODUCTIVITY OF
D
ROUGHT
-
STRESSED
C
ROPS BY
F
OLIAR
A
PPLICATION OF
A
LKANOLAMINES
Hans Bergmann and Gerhard Gramss
Friedrich-Schiller-University, Institute of Geological Sciences,
Burgweg 11, D-07743 Jena, Germany
A
BSTRACT
Losses in biomass production and protein caused by stress factors such as drought,
waterlogging, salinity, or heavy-metal contamination are accompanied by structural
damages to cellular membranes of crop plants, to alterations in enzyme activities, and to
cytoplasmic dehydration. Water deficit leads to the closure of stomata, to reduced uptake
of aerial CO
2
, and thus to the inhibition of photosynthesis and the excessive formation of
reactive oxygen species in chloroplasts and other cell compartments. Stress-activated
phospholipases and esterases catalyze the separation of ethanolamine (EA), choline, and
their phosphate esters, as well as fatty acids and serine from the phospholipid molecule of
cell membranes. The membrane protein component is subject to proteolysis. The
liberated serine is a precursor for the formation of further EA and choline. In a research
project extending over 3 decades, the membrane lipid moieties, ethanolamine and choline
were applied at 1.5 kg/ha as a foliar spray to potted cereal plants and to cultures in more
than 150 field trials. External application of the biogenic stress metabolites was expected
to initiate the plants' resistance and tolerance mechanisms by pretending a stress
situation. Actually, the treatment confined yield losses in drought-stressed wheat, rye,
and barley by stabilizing water household, photosynthesis, and protein production.
Relative to untreated, drought-stressed plants, increases in biomass (5-20 %) and protein
content (5-7 %) were recorded in 14 to 58 % of the experiments which had been
conducted at 17 Experimental Agrostations of different soil conditions but little climatic
extremes. Plant responses were significant under drought conditions and on poor soils.
They were negligible in the absence of abiotic stress. The major short- and long-term
stress responses were followed on the biochemical and ultrastructural level. Under the
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