Agriculture Reference
In-Depth Information
the principal cause of BER in tomatoes, even when the uptake of calcium by the
plants seemed to be adequate.
Dorais et al. (
2001
) and Wu and Kubota (
2008b
) examined the effects of electri-
cal conductivity (EC) on tomato fruit yield and found that it is not reduced when
EC was increased moderately to approximately 5 dS m
−1
. Wu and Kubota (
2008b
)
reported that for all cultivars tested the plant physiological response under elevated
EC was cultivar and growth-stage specific, and increasing the inflow EC to mod-
erate levels during the reproductive growth stage did not adversely impact photo-
synthesis, transpiration, and leaf conductance of tomato plants. According to Zushi
et al. (
2009
), salt stressed fruit developed protection mechanisms against salt-in-
duced oxidative stress during the ripening in both the pericarp and pulp. In addition,
the growers and investigators have developed some growing strategies to overcome
or mitigate the detrimental effects of salinity.
Strategies to Overcome or Mitigate Salinity Stress
Numerous strategies have been tested for minimizing crop yield loss due to salinity,
and at the same time maximizing inner (nutrient value, taste, texture) and outer (ap-
pearance, color, firmness, shelf life, aroma) quality characteristics of the marketable
product. Those management practices include nutrient management of salt-stressed
crops, timing of salinity application or withdrawal, method and scheduling of irriga-
tion, and the choice of rootstock (Grieve
2010
). Generally, it could be said that high
water supply has a mitigation effect on salinity, and vice versa: drought situations
increase these effects. The important fact is however the choice of the right cultivar.
Salt tolerant cultivars are the best tool to avoid or mitigate this kind of stress, e.g.
in semiarid greenhouse conditions and with limited environmental control capacity.
There are other irrigation and agronomic strategies that can also minimize salin-
ity damage. One of these strategies involves crop spraying or the application of
supplemental nutrients, fluctuating EC-values and the use of a split root system with
unequal ECs. For instance, Tuna et al. (
2007
) reported that salt stress significantly
decreased plant growth and fruit yield. Supplementary calcium sulphate was added
however to the nutrient solution and it significantly improved plant growth and fruit
yield and improved membrane permeability.
Buck et al. (
2008
) lowered the EC-values during the midday, in order to miti-
gate high water stress on the tomato plant, and achieved a premium-grade tomato
yield comparable to the high EC-treatment. These results are in agreement with
those of Santamaria et al. (
2004
) where the authors found that a 2 dS m
−1
day-
time EC combined with 6 dS m
−1
nighttime EC level did not affect total yield,
fruit number, fruit weight, or plant water consumption in the cherry tomato. This
strategy makes sense for use in semiarid greenhouse conditions with limited con-
trolled-environment technology. Sonneveld (
2000
), Mulholland et al. (
2002
), Ta-
batabaie et al. (2004), and Lycoskoufis et al. (
2005
) suggested for crop growing
in soilless culture an unequal EC, achieved with a “split-root” system, in order
to avoid or mitigate high salinity issues, and as a consequence, to improve both
