The Influence Of Priming Two Cucumber Cultivar Seeds

J. Duhok Univ. Vol.13, No.1, (Agri. And Vet. Sciences) Pp 94-102, 2010
Syrian cultivar manifested superiority over
Aquadulce, Taka357 and Babylon in the number
of normal epidermal cells of leaf upper surface
by 8, 23.9 and 13%, respectively, and likewise
over Taka357 and Babylon in the leaf lower
surface, respectively, by 23.5 and 15.1%
(table, 3). The highest aperture width for upper
and lower leaf surfaces were accompanied with
Taka357 which highly exceeded other cultivars.
This cultivar was exceeded Aquadulce and
Syrian aperture width of upper leaf surface
stoma by 10.6 and 10.8%, respectively, and in
stoma: epidermis cells ratio by 18.2 and 25%,
respectively, (table, 2). Local Syrian cultivar
initially possesses higher epideral cells and
stomata numbers per unit area as compared to
other cultivars, especially Taka357. Drought
highly increases the stomata population for unit
area but not for entire leaf. This paradox
emerges from the huge effects of drought on cell
expansions rather than cell divisions in which
new stomata are created, since almost cell
divisions are determined during leaf
differentiation. There are numerous examples of
plasticity in stomata densities within species,
with changes readily induced through exposure
of developing leaves to changed atmospheric
CO2 concentrations (Woodward et al., 2002 and
Hetherington and Woodward, 2003).
The highest stomata width on leaf upper
surface (7.2 μm), stomata aperture (2.7 μm) on
leaf lower surface and stoma aperture on leaf
upper surface (2.39 μm) were observed in
Taka357 sprayed by 2x10 -3 M ABA. Untreated
aquadulce revealed the highest magnitude of leaf
upper surface stoma length (11.39 μm). The
highest number of epidermal cells (6185.5) and
stomata length (8.1 μm) on leaf lower surface
were coincided by Aquadulce sprayed with
2x10 -3 M ABA (tables, 2 and 3). Twowaytha
plants sprayed with 2x10 -6 M ABA displayed the
highest stoma number on upper and lower leaf
surfaces 1467.7 and 2201.6 stoma.mm -2 ,
respectively. Finally untreated check of Babylon
was superior over other treatments in the ratio of
stoma: epidermis on upper and lower leaf
surfaces 0.45, 0.5, respectively, and likewise in
number of leaf upper surface stoma 1467.7
stomata.mm -2 . Drought resistant plant possesses
lower stomata population and larger aperture
area to facilitate CO2 exchange that sustains
reasonable photosynthesis under drought
adversity (Abdel, 1982). Franks et. al. (2001)
reported that as a pressure was increased from as
low as 0.3 MPa to as high as 5.0 MPa, guard cell
volume increased in a saturating fashion. The
elastic modulus was calculated from these data
and was found to range from approximately 2 to
40 MPa. The data allow inference of guard cell
osmotic content from stomatal aperture and
facilitate accurate mechanistic modeling of
epidermal water relations and stomatal
functioning. ABA modifies the stomata
dimensions, particularly aperture to acquire plant
more efficient CO2 exchanges and thereby
photosynthesis. However, it reveals temporary
reduction. Terashima et. al. (1988) found that
after the ABA treatment, the response of
photosynthetic CO2 assimilation rate, A, to
calculated intercellular partial pressure of CO2,
Pi, and [A (pi) relationship was markedly
depressed in H. annuus. A less marked
depression was also observed in V. faba.
However, when the abaxial epidermis was
removed from these leaves, neither the maximum
rate nor the CO2 response of photosynthetic
oxygen evolution was affected by the application
of ABA.
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