PHYSIOLOGICAL STUDIES
ON SOME ORNAMENTAL TREES AND SHRUBS
Mohamed Refaat Ibrahim Magouz
ABSTRACT
This study was carried out at the Experimental Farm of the Faculty of
Agriculture, Kafr El-Sheikh University during two successive seasons (2006 and
2007). This study included two experiments in each season. The first experiment
aiming to study the effect of soil salinity (sodium chloride and calcium chloride
mixture at ratio of 1: 1 by weight at the concentrations of 0.0, 0.4, 0.8, 1.2 and 1.6 g
salt/100 g soil) and paclobutrazol at 0, 25, 50 and 75 ppm on the growth and chemical
constituents of Hibiscus rosa-sinensis L. transplants. Foliar application of a
paclobutrazol added at two times, the first one was done on May 15th and repeated
again after 30 days in early morning. The second experiment was to study effect of
three levels of nitrogen (3, 6 and 9 g N/plant added in two equal doses on April 15th
and May 15th) and sulphur (added in one dose on April 15th at the rates of 1, 2 and 3 g
S/plant) on the growth and chemical constituents of Hibiscus rosa-sinensis, L.,
Lantana camara, L. and Citharexylum quadrangulare, J. transplants. The obtained
results could be summarized as follows :
First experiment :
Salinity treatments markedly reduced growth characters in Hibiscus rosasinensis, Linn. plants, when compared to the control. The control and 0.4% NaCl +
CaCl2 (1: 1) mixture salts treatment produced the highest values of survival
percentage, plant height, number of branches and roots/plant, stem diameter, root
length and fresh and dry weight of vegetative parts and roots. All salinity levels
markedly increased Na+ and Ca++ percentages and decreased Chlorophyll (a and b)
content, N, P and K percentages in the leaves of Hibiscus rosa-sinensis, L. compared
to the control. Increasing NaCl + CaCl2 (1: 1) mixture more than 1.2% was lethal to
Hibiscus transplants. Paclobutrazol generally improved vegetative growth and roots
parameters. However, spray of paclobutrazol at high rate (75 ppm) had the most
pronounced effect on growth of Hibiscus rosa-sinensis L. transplants in the majority
of treatments. The data suggested that paclobutrazol promoted salt stress avoidance of
Hibiscus rosa-sinensis, L. plants by reducing the accumulation of harmful Na+ and
Ca++ ions in the leaves of plants and improved N, P and K absorption.
Second experiment:
All nitrogen and sulphur application levels significantly increased the most
vegetative growth parameters (plant height, root length, number of branches and
roots /plant, stem diameter and fresh and dry weight of vegetative parts and roots )
over the control of Hibiscus rosa-sinensis, L., Lantana camara, L. and Citharexylum
quadrangulare transplants. Using nitrogen and sulphur at high level (9 g N and 3 g
S/plant) had the greatest effect for increasing all vegetative growth and roots
parameters of the three plants compared to control. All nitrogen and sulphur
application levels increased chlorophyll (a), (b) contents, N, P and K% in the leaves
over the control of the three plants. However the highest values resulted from using
high level (9 g N and 3 g S/plant) in the two seasons.