Abstract:
In order to determine the best growing media for
Gerbera jamesonii
under alkaline
conditions, a factorial experiment was conducted wi
th two factors, namely: (i) Growing
medium, and (ii) Concentrations of bicarbonate (NaH
CO
3
) in nutrient solution. Results
showed that increasing the concentration of NaHCO
3
from 0 to 40 mM in nutrient
solution significantly decreased plant growth, maxi
mal quantum yield of PSII
photochemistry (F
v
/F
m
), photosynthesis Performance Index (PI), Glutamine
Synthetase
(GS) activity, Leaf Relative Water Content (LRWC), C
hlorophylls (Chl a, b and total
Chl) and carotenoids. Under alkalinity stress, redu
ction in vegetative growth,
F
v
/F
m
, PI
,
LRWC
, GS activity and photosynthesis pigments content w
as the lowest in Coconut Fiber
(CF) substrate compared to the other substrates. Fu
rthermore, plants grown in CF
substrate had higher soluble sugars and proline con
tent than those in other substrates. On
the other hand, plants grown on Perlite (P) substra
te had the highest reduction in growth
and physiological characteristic in alkaline condit
ions. The alleviation of alkalinity-
induced growth inhibition of plants by CF substrate
may be related to improvement of
photosynthesis, enhancement of GS enzyme activity a
nd osmotic regulation. It is
concluded that the use of CF substrate could provid
e a useful tool to improve alkalinity
tolerance of gerbera plants under NaHCO
3
stress.
Keywords:
Alkalinity, Glutamine synthetase activity, Growing
media, Osmotic adjustment,
Photosynthetic pigments.
