STABILIZING PRODUCTIVITY OF DROUGHTSTRESSED CROPS BY FOLIAR APPLICATION OF ALKANOLAMINES - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 233

Untreated EA treated

8000

7000

6000

5000

4000

3000

2000

1000

Subsoil
density
in g/cm3

0

1,4 1,5 1,6 1,7 1,4 1,5 1,6 1,7

Topsoil 1.25 g/cm3 Topsoil 1.35 g/cm3

Figure 6. Effect of ethanolamine (EA; 1.5 kg/ha) on the grain yield (kg/ha) of wheat ( T. aestivum cv .
Alcedo) grown on two loamy top soils which cover clay-loam subsoils in four density states. Yield
increases given in percent refer to the yield of the untreated control (100 %). Mean precipitation from
shooting to grain filling 1.5 mm/day.
a, percentage increases are significant at p < 0.05.
Field experiments conducted by Experimental Station Grossobringen, Thuringia, Germany, over 3 yr.

5. H OW DO A LKANOLAMINES A CT ?

With the degradation of membrane phospholipids and proteins (e.g., Lin and Wu 1996)
and the reduced protein synthesis in favour of the formation of free amino acids under abiotic
stress, the building stones of antiproteolytic, osmoprotective, radical scavenging, cell growth
promoting, and cell wall strengthening compounds are provided (Figure 1; Bergmann et al.
1999). Foliar applications of alkanolamines at < 0.5 mg to plants prior to the initiation of
stress had immediate remediating effects (e.g., Bergmann et al. 2002; Mascher et al. 2005).
With uptake of the applied [ 14 C]EA (MW 61.08) at a rate of 10 % (Eckert et al. 1988a), its
concentration in plants of 0.25 g dry weight should increase by < 0.2 mg/g. The concentration
of 3.8 to 4.8 mg/g in its transformation product, glycine betaine (MW 117.15; Bergmann et
al. 2002) in drought-stressed barley tissue could then theoretically rise by < 0.38 mg/g. In
practice, however, EA application lowered the glycine betaine concentration in treated barley
to 3.3 to 3.8 mg/g dry weight (Bergmann et al. 2002). A key position of the cell membrane
stabilizing glycine betaine (Bewley 1979; Greenway and Munns 1980) in stress control must
therefore be denied. Its foliar application to maize alleviated nevertheless stress symptoms
caused by water deficit (Ashraf et al. 2008; Lippmann and Bergmann 1995). This
osmoprotectant is believed to stabilize photosystem II protein complexes in higher plants
(Yeo 1998). A 48-h pre-treatment with EA prevented disintegration and burst of barley
chloroplasts by superoxide radicals which had been formed after the exposure to the