Liquid Culture Systems for in vitro Plant Propagation

Nutrition of plants in greenhouses and in vitro 479
at 4.0 – 5.0 mS cm -1 , when changing tomatoes from vegetative to generative
growth, or when a higher dry matter content and a better taste are required
for the tomato fruit (Adams, 2002).
During vegetative plant propagation, the EC is kept at 0.8-1.2 mS cm -1 in
the growing medium, while for growth of established plants the conductivity
should be raised to 1.5 – 2.0 mS cm -1 , measured by the SSE-method (Soil
Saturated Extract). By increasing the conductivity and the concentration of
the nutrient elements, the uptake will increase as long as the growth
increases, but when the growth start to decrease because of an increasing
conductivity, the total nutrient uptake also decrease (Table 1). How quickly
a decrease in growth will commence because of increased conductivity
depends of the humidity of the growing medium. Plants in dry medium give
quicker response to conductivity than plants in a wet medium.
Uptake of Ca + increases with increasing concentration of Ca + , when the
amount of the other elements are constant. By increasing conductivity, the
uptake of Ca + usually decreases (Table 2). If, on the other hand, only Ca + is
increased in the nutrient solution, the uptake of Ca + will also increase
(Gislerød, 1997).
Table 1: Effect of salinity (EC) on the uptake of water (l) and nutrients (g) by tomato plants
in NFT from April till August (from Adams, 1994)
EC of nutrient solution (mS cm -1 )
3.2 4.8 6.6 7.8 9.3
Uptake per plant
Water (l) 98 109 105 93 82
N (g) 24 26 25 23 21
P (g) 6.0 6.4 5.7 5.1 4.6
K (g) 31 35 30 28 23
Table 2: The effect of salinity (EC) on growth and Ca accumulation by cucumber plants
grown in NFT for 7 weeks in autumn (from Adams, 1994)
EC of nutrient solution (mS cm -1 )
3.0 5.5 8.0
Dry weight per plant (g) 140 113 76
Total Ca in plant (g) 4.71 (3.4 %) 3.44 (3.0 %) 1.62 (2.1 %)