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Results and
Discussion
Epidermis refers to the outermost layer of cells of all parts of
the primary plant body-stems, roots, leaves, flowers, fruits, and
seeds. The normal functions of epidermis of the aerial plant parts
are considered to be restriction of transpiration, mechanical
protection, gaseous exchange through stomata, storage of water and
metabolic products, and photosynthesis.
Experimental results revealed that thickness of epidermis ranged from
5.91 microns (Snoopy rye) to 13.1 microns (UPT 72142), and epidermal
cells of the tall wheat varieties were thicker than those of the
dwarf ones (Table
1). This,
however, was not true for triticales and ryes. Amongst triticales
three dwarf triticales, TL 419, UPT 78274 and UPT 7440 had a thicker
epidermis than one tall strain, i.e., UPT 74303. Two tall wheats, UP
031 and C 306, which showed maximum lodging, had thicker epidermis
than all the dwarf varieties with better lodging resistance. Also, UP
301 which showed no lodging and gave a high yield (41.5 q/ha) had the
lowest value for this character. UPT 72142 had the thickest epidermis
among all the triticales though it showed high lodging. Amongst ryes,
Snoopy had the least lodging as well as the thinnest epidermis.
Thickness of epidermis does not show any role in lodging resistance
in our study.
The term sclerenchyma refers to complexes of thick walled cells,
often lignified, whose principal function is mechanical. These cells
are supposed to enable plant organs to withstand various strains,
such as may result from stretching, bending, weight and pressure,
without undue damage to the thin-walled softer cells.
Thickness of sclerenchymatous cells varied from 9.45 microns in UP
301 to15.46 microns in UPT 72142 (Table
1). Dwarf wheats,
with the exception of UP 301, gave a thicker sclerenchyma than the
tall wheats. The dwarf wheats, WL 711 and UP 2003, with thick
sclerenchyma cells were more resistant to lodging than the tall ones.
UP 301, though completely lodging resistant and high yielding, had
the lowest value for sclerenchyma thickness. Since this variety is
very short in stature, it does not lodge in spite of thin
sclerenchyma cells. Sclerenchyma was found to be thicker in all the
four dwarf triticales when compared to UPT 74303 and UPT 78015, but
the thickness was maximum in UPT 72142 which is tall and high
yielding. UPT 72142 had lodging on the higher side in spite of the
thickest sclerenchyma which may be due to the thinnest hypodermis.
Similar correlation is seen in UPT 7440 which shows maximum lodging
in spite of having less plant height. In general, thick sclerenchyma
resulted in less lodging. Amongst ryes this relationship is clear
cut. Murdy (1960) in maize and Vaidya (1956) in wheat reported that
the thickness of sclerenchyma was greater in lodging resistant
varieties.
One or more layers of cells beneath the epidermis in leaf, stem, and
root may be morphologically and physiologically distinct from the
deeper-lying ground tissue. This may be known as hypodermis.
The relationship between hypodermis and lodging resistance followed a
pattern more of less similar to sclerenchyma (Table
1). Wheats with
thicker hypodermis showed the least lodging except UP 301 which did
not lodge in spite of having a thin hypodermis due to its very less
height. UPT 72142 had the thinnest hypodermis amongst triticales but
it did not show too much lodging, which may be due to its thickest
sclerenchyma. The two dwarf triticales. UPT 78274 and UPT
78268 had higher values and the least lodging. Another dwarf
triticale UPT 7440 showed a thinner hypodermis and also the maximum
(20 per cent) lodging amongst triticales. Amongst ryes thick
hypodermis results in less lodging. Gobo et al (1971) gave similar
results in wheat.
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