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International Journal of Horticulture 2014, Vol.4, No.7, 32
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which is realistic in the field because in years with
infrequent rain, salt spray is not washed off during the
summer growing season (Cheplick and Demetri, 1999).
4.3 Measurement of agronomic parameters
Variables recorded were percentage survival, shoot
length and stem girth. Stem length was measured from
the soil level to the terminal bud with meter rule. Leaf
area meter (LI-COR 300 model) was used to measure the
area of the first three fully expanded leaves. Stem girth was
measured at about 5 cm from stem base using a digital
vernier caliper (model 0~200 mm). Only the leaves on
individual plants and number of branches were counted.
4.4 Fresh and dry mass determination
After 12 weeks, plants were destructively harvested,
partitioned into leaves, stems and roots. The roots were
rinsed with water and the major ones were counted and
their length measured. Fresh plant parts were weighed
separately before their dry mass was measured after
oven-drying to constant weight at 70°C. Derived variables
were Root: Shoot ratio (root mass/shoot mass) and the
relative growth rate-RGR- (ln mass2-ln mass1)/ time.
4.5 Water status and chlorophyll content
Percentage moisture content of plant parts was
calculated with the formula: [(fresh mass– dry mass) /
dry mass]×100. Plant xylem water potential was
measured with a plant moisture-stress instrument (PMS
Instrument Co. Oregon, USA) on six randomly selected
stems from each treatment. Pre-dawn xylem water
potential was taken between 06.00 and 07.00 am while
mid-day xylem water potential was measured between
12:00 noon and 1:00 pm. Leaf total chlorophyll was
extracted following the method of Arnon (1945) and
calculated with the formula: (20.2×D
645
+8.02×D
663
) ×
(50/1000)×(100/5)×½, where D=absorbance.
4.6 Soil and phytochemical analyses
Dried plant and soil samples were assayed for mineral
contents following the standard methods of the
Association of Official Analytical Chemists (AOAC,
1985) in the Central Laboratory of The National
Institute for Oil Palm Research (NIFOR), Nigeria.
4.7 Stomata number, necrosis and visual ratings
determination
Leaf stomata and necrosis were estimated on the leaves
used for the determination of moisture content. The
adaxial and abaxial surfaces were covered with a layer
of nail polish following the method used by Hwang and
Chen (1995). This was left to dry and carefully removed
from the leaf surface, placed on a microscopic slide and
observed under the light microscope with digital camera
attachment. The stomata was counted and expressed per
unit leaf area. The stomata number per leaf was
estimated as the product of stomata density and leaf area.
The area of leaf tissue with necrotic damage was
measured using a dot grid and expressed as the
percentage of total leaf area showing necrosis (Griffiths
and Orians, 2003; Griffiths et al., 2006). Visual ratings
was conducted by six observers based on foliage
appearance, with 1=no green foliage, 2=25% green
foliage, 3=50% green foliage, 4=75% green foliage and
5=all green foliage (Scheiber et al., 2008). Although
quality standards differ, researchers deem ratings of 1
and 2 as unacceptable, 3 as marginally acceptable, and
ratings of 4 and 5 as acceptable in most professionally
maintained landscape situations (Scheiber et al., 2008).
4.8 Experimental design and data analysis
The experiment was conducted in a completely
randomized design with six single-plant replicates. Data
were subjected to single factor ANOVA and means were
separated with Turkey Honest Significant Difference
(HSD) test with SPSS version 17.0 (SPSS Inc. Chicago,
IL, USA) at P≤0.05.
Acknowledgements
I acknowledge Dr O. F. Olotuah and Dr. O. A. Obembe in the
Department of Plant Science and Biotechnology, Adekunle Ajasin
University, Akungba Akoko, Ondo State, Nigeria for proofreading
the manuscript painstakingly and offer of valuable suggestions. I
appreciate Mr Okerenwogba M. B. Mr Joseph Jack Udoh and Mr
Omoruyi Efe in the research laboratories of the National Institute
for Oil Palm Research (NIFOR) Nigeria for their support during
the analyses of soil and plant samples.
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