Biochemical. physiological and morphological responses of sugar beet grown
in sandy soil under three levels of NaCI salinity in irrigation water. Le. control, 3000
and 6000 ppm were studied in pot experiment. Results showed that, root fresh weight
linearly decreased by increasing NaCI salinity levels up to 6000 ppm, but sucrose
percentage in root was significantly increased. On the other hand, increasing NaCI
levels resulted in significant increase of Na content in both of shoot and root.
Meanwhile. K content in shoot was sharply decreased but K content in root didn't
significantly differ by increasing NaCI levels. Also, under salinity results indicated a
strongly negative correlation between shoot osmotic potential and shoot Na content
while it was mainly with sucrose concentration in root. Thus, sugar beet plant has an
active mechanism to include higher amount of Na in leaves and utilizes it to regulate
leaves osmotic potential under saline condition. Despite of this mechanism the
transpiration rate and stomatal conductance showed significant decrease by
increasing NaCI levels up to 6000 ppm. Moreover. stomatal behavior and stomatal
morphOlogy revealed a gradual response to the level of NaCI salinity used. Stomatal
density, stomatal area and stomata pore area Significantly decreased by adding Ihe
first saline level (3000 ppm) but no response was detected for stomatal closure at the
same saline lever. No further response was shown for stomatal area by increasing
NaCI from 3000 to 6000 ppm. while stomatal closure recorded 60% in lower e. 30% in
upper leaf surface at 6000 ppm NaCllevel. Generally it could be pointed out that, the
decrease of sugar beet root fresh weight at low salinity level (3000 ppm) might be due
to osmotical stress. While at high level of NaCI (6000 ppm) it was attributed to toxic
effect of higher NaCI accumUlated on photosynlhesis tissues which led to dose the
stomata in order to inhibit more Na transporting into leaves.