PDF file - Israel Trade Commission

Agriculture 2011
Table 1: Average concentrations of saline elements (g/kg, DW) in
different organs of non-grafted and grafted plants irrigated with
effluent water ± SE (unpublished data).
more selective and absorbed less B than of the melon
roots. The B-exclusion hypothesis is supported by other
studies: Dannel et al. (1998, 2002) suggested that at
low B concentrations, B uptake may be active, but at
high concentrations, there is evidence of B excretion or
exclusion. Dordas et al. (2000) indicated that B enters
plant cells partly by passive diffusion through the lipid
bilayer of the plasma membrane and partly through
proteinaceous channels. Dordas and Brown (2001)
examined B transport in squash plants, and suggested
that both of these mechanisms were possible.
Saline elements in the plant tissues
The effects of grafting watermelon (‘Tri-X 313’) onto the
commercial Cucurbita maxima × Cucurbita moschata
rootstock TZ-148 on growth and yields of plants irrigated
with saline water (EC 4.5 dS/m) in disease-free soil
in experimental field plots in an arid zone in southern
Israel are shown in Fig. 4. Vegetative growth, fruit yield
and fruit sizes of the grafted plants were higher than
those of the non-grafted plants (Fig. 4). The differences
in yield parameters were probably due to the higher
salt tolerance of the grafted vs. non-grafted plants or to
higher excretion or exclusion of saline ions by the root
system of the grafted plants.
Fernandez-Garcia et al. (2003) showed that under
saline conditions (60 mM NaCl), Cl - and Na + uptake
by grafted tomato plants is significantly lower than
that by non-grafted plants, indicating that the former
exhibit higher selectivity toward saline absorption than
the latter. Likewise, Romero et al. (1997) found that the
effects of salinity on two varieties of melon grafted onto
three hybrids of squash were less severe than those on
non-grafted melons, suggesting that the grafted plants
develop various mechanisms to prevent the physiological
damage caused by excessive accumulation of Cl - and
Na+ in the leaves. The suggested mechanisms included
exclusion of Cl - and/or reduction of its absorption by the
roots, and replacement or substitution of total Na + with
total K + in the foliage.
The concentrations of Ca, Na, Mg, and Cl - in the leaves,
stem, and fruit tissues of a non-grafted melon (cv.
Arava) plant and melon grafted onto pumpkin rootstock
(TZ-148) grown in field plots in the experimental station
in Akko are presented in Table 1. These plants were
irrigated with secondary effluent. The concentrations of
all saline elements except Mg in the stem and leaves
were higher in the non-grafted vs. grafted plants (Table
1). The largest difference between the non-grafted and
grafted plants was in their Na concentration, which
was one order of magnitude lower in the grafted plant
tissues than in the non-grafted ones.
Edelstein et al. (2010) suggested two mechanisms that
might explain the decrease in shoot Na concentration in
plants with pumpkin rootstocks: (i) Na exclusion by the
pumpkin roots, and (ii) Na retention and accumulation
within the pumpkin rootstock. Quantitative analysis
performed by Edelstein et al. (2010) indicated that the
pumpkin roots excluded ~74% of available Na, while
there was nearly no Na exclusion by melon roots. Na
retention by the pumpkin rootstocks decreased its
amount in the shoot by an average 46.9% compared
to uniform Na distribution throughout the plant. In
contrast, no retention of Na was found in plants grafted
on melons.
Conclusions
Intensive agriculture has increased the use of toxic
chemicals on cultivated lands. In addition, to satisfy the
demand for food in arid and semiarid regions, the use
of marginal water sources, such as treated domestic
sewage (effluent) and saline water, for irrigation is on the
rise. These can enhance soil and water contamination,
and the possibility of toxic microelements and saline
elements entering into the food supply chain via plants.
From laboratory, greenhouse and field experiments,
it can be concluded that grafting of vegetable plants
can be used as a technique to prevent the entry of
toxic microelements and saline elements into the food
chain.
References
References are available at the corresponding author
medelst@volcani.agri.gov.il
16