Page 29 - Volume 1, Issue 1, January 2008

Effect of N on Fe, Mn, Zn & Cu concentration in lettuce and spinach 27
form of nitrogen supply play a pivotal role
in the mineral nutrition of plants; e.g. the
form of N supply controls the uptake ratio
of cations and anions and influences dry
matter production (5, 6).
The aim of the current work was to study
the effect of several nitrogen application
rates on concentration of Fe, Mn, Zn and
Cu in lettuce and spinach in order to obtain
some information, which could improve
their nutritional status and productivity.
Materials and Methods
1. Plant culture and treatments
Three separate experiments (A, B and
C) using lettuce and spinach plants were
carried out successfully.
Experiment Awas conducted in a glass-
house, from March to May 2001, in hydro-
ponics. Seedlings of Butterhead lettuce
(cv. Divina) were grown in sand culture
without supplementary heating and light-
ing; the day and night temperature were
20-25 0C and 10-150C, respectively. The pots
were arranged in a complete randomized
block design with 4 replicates and 7 nitrate
nitrogen levels (N1:0.1, N 2:0.5, N3:1.0, N 4:2.0,
N 5:4.0, N6:7.0, N7:14.0 mM NO3-N).
Experiment B was conducted in a com-
mercial vegetable field from March to
April 2002; data concerning soil analysis of
the experimental field are shown in Troy-
anos et al. 2004a (12). Lettuce seedlings
Romaine (cv. Toledo) at 3-4 leaves growth
stage were transplanted in the field. One
week after transplanting, six nitrogen fer-
tilization rates (N1:0, N2:45, N3:90, N4:135,
N5:180, N6:225 kg Ν/ ha ) were applied by
using ammonium nitrate fertilizer (33.5%
N). The experimental design was Latin
square with 6 rows and 6 columns along
the longest direction of the plot area (30
x 6 m) which was divided into 36 plots.
More details about plant culture, exper-
imental designs and data analysis of the
effects of nitrogen application rate on the
growth characteristics and nitrogen study
in both lettuce experiments, are present-
ed elsewhere (12, 13).
In experiment C, spinach seedlings of
the curly leaved variety Viroflay were grown
in sand culture, in the aforementioned
glasshouse, from December 2001 to Febru-
ary 2002. The mean monthly air tempera-
tures were 10 0C, 130C and 160C, respectively.
The pots were also arranged in a complete
randomized block design with 4 replicates
and six nitrate nitrogen concentrations (N1:1,
N2:3, N 3:6, N4:10, N5:16 and N6:22 mΜ NO3-N).
Nutrient solutions in experiments A
and C were applied manually using 250 ml
of modified Long Ashton nutrient solution
per plant per day (2). Nitrogen was applied
as calcium nitrate and the differences in the
concentration of Ca in the nutrient solution
resulting from the different nitrogen regime
were compensated by the addition of CaCl2.
In all experiments different harvests
were performed during the growth of
plants but the data from the fifth harvest
are presented here; the total number of
plants analyzed was 28, 144 and 24 for ex-
periments A, B and C, respectively.
2. Determination of Fe, Mn, Zn and Cu
concentration in the foliage and roots
In experiments A and C, after the remov-
al of the plants from the pots, they were di-
vided into foliage and roots and they were
carefully washed three times with deionised
water. In the field experiment only the
heads were cut and their fresh weight was
taken. The plant material was dried to con-
stant weight in a forced draught air oven at
800 C, weighed and dry-ashed in a furnace at
5000C. The dry digest was extracted in 1N
HCL, and the concentration of Fe, Mn, Zn
and Cu was determined by using a Varian
A220 atomic absorption spectrometer.
3. Statistical analysis
The statistical analysis was carried out