الفهرس 
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Abstract
Two field experiments were carried out during the seasons of 2014 and 2015 respectively at the Experimental Farm, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Egypt to study the effect of foliar application of CaCl2 (5 and 10 mM), ascorbic acid (AsA, 50 and 100 ppm), putrescine (Put, 0.1 and 0.2 mM) and distilled water as control on sunflower plants under water deficit conditions. Two irrigation levels according to the field capacity (FC) were investigated; the well-watered plants were irrigated when the value of FC between 55-65% whereas; the water-stressed plants were irrigated when the value of FC between 25-35%.
The results could be summarized as follow:
5.1. Changes in growth parameters
Water deficit caused significant decreases in all studied growth parameters of sunflower plants including the fresh and dry weights for leaves and stem compared to the control plants in both seasons. Different foliar treatments enhanced significantly all investigated growth parameters compared to the control plants in both seasons; in this regard; the higher concentrations of foliar substances were more effective than the lower ones. The interaction effect between the irrigation level and different foliar application revealed that there were multiple influences for the foliar treatments on growth parameters under both investigated irrigation levels.
5.2. Changes in leaf water status
Water deficit caused a significant decrease in leaf relative water content (LRWC) compared to the well-watered plants. All examined foliar applications except CaCl2 at 5 mM in the first season and AsA at 50 ppm in the second one increased significantly LRWC in comparison with the untreated controls. The interaction effect between the irrigation level and different foliar applications showed that the treatments of CaCl2 at 10 mM gave the highest significant in LRWC under both examined levels of irrigation in both seasons.
5. 3. Changes in leaf pigments
5. 3. 1. Chlorophylls
Inadequate water supply caused high significant decreases in the concentration of Chl a, Chl b, total chlorophylls (Chl a+b) and Chl a/b ratio compared to those of the well-watered plants in both seasons. All foliar treatments enhanced significantly Chl a, Chl b and Chl a+b compared to the control plants in both seasons. Generally, the highest significant results in the triple chlorophyll traits (Chl a, Chl b and Chl a+b) were detected by the treatment of Put at 0.2 mM in both seasons respectively; whereas, the increases obtained by treatments of AsA at 100 ppm or Put at 0.1 mM just reached to the same level of significance with Put at 0.2 mM in the second season. A similar trend was observed in the plants treated by CaCl2 at 10 mM in respect to Chl a and total chlorophyll (Chl a+b) only in the second season.
In contrast, all foliar treatments except CaCl2 at both examined concentrations caused significant decreases in Chl a/b ratio in comparison to control plants in both seasons. The lowest significant findings were obtained by the treatments of Put at 0.1 and 0.2 mM in the first season; and AsA (50 or 100 ppm) or Put at 0.2 mM in the second season.
Concerning the effect of interaction between the irrigation level and different foliar applications; it was obvious that under well-watered conditions, the treatment of CaCl2 at 10 mM achieved the highest significant increases in Chl a, Chl b and Chl a+b in comparison to the control plants in both seasons; while, under water stress conditions; Put at 0.2 mM resulted in the highest significant increases in Chl a, Chl b in the first season and Chl a+b in both seasons respectively compared to the control plants.
As for the Chl a/b ratio, an opposite trend with significant decreases was noticed in the plants treated by Put at 0.1 or 0.2 mM under unstressed conditions in the first season; whereas; under water stressed conditions all investigated treatments of AsA or Put revealed significant decreases in this trait compared to the control plants in both seasons.
5. 3. 2. Carotenoids
Water stressed plants revealed a significant reduction in the concentration of carotenoids compared to the unstressed ones in both seasons. The treatments of AsA at 50 ppm, Put at 0.2 mM followed by Put 0.1 mM gave the highest increases in carotenoids comparing to the other treatments. These increases reached the level of significance compared to the control plants in the first season. The interactive treatment of Put at 0.2 mM with both irrigation levels reflected that there were significant increases compared to the control plants under well-irrigated and drought stress conditions in both and first season respectively. Plants subjected to water deficiency revealed significant increases in carotenoids / Chl (a+b) ratio compared to those of the well-irrigation level in the two seasons. There were significant decreases in carotenoids / Chl (a+b) ratio as affected by the most examined foliar treatments. No significant differences were detected in carotenoids / Chl (a+b) ratio between all foliar treatments and the high level of irrigation. On the contrary; under drought stress; there were several significant decreases in this trait compared to the control plant in both seasons.
5. 3. 3. Anthocyanins
There was a significant increase in the concentration of anthocyanin in the water-stressed plants compared to the well-irrigated ones in both seasons. All investigated treatments increased significantly the concentration of anthocyanins compared to the control plants in both seasons. In this context, the treatment of Put at 0.2 mM caused the highest significant values in the two seasons. All foliar treatments under both examined irrigation levels led to significant increases in anthocyanins compared to the untreated control in the two seasons. The highest significant increases were observed by the treatment of Put at 0.2 or 0.1 mM in both seasons respectively.
5. 4. Changes in organic osmolytes
5. 4. 1. Proline
Plants under drought stress revealed considerable significant increases in proline concentration compared to those of the well-irrigated ones in the two seasons. All plants which treated by CaCl2 or Put regardless of concentration showed high significant decreases in proline, while those subjected to AsA revealed insignificant increases in this trait compared to the controls in both season respectively. no significant differences were detected between most foliar treatments in the proline concentration under well-watered conditions in both seasons; while, a significant decrease was observed clearly between the treatments of CaCl2 or Put and the control plants under inadequate irrigation level. The lowest concentration of proline was detected by the treatment of CaCl2 at 10 mM in the two seasons respectively.
5. 4. 2. Soluble sugars
Inadequate water supply significantly increased the concentration of soluble sugars in leaf tissues of sunflower plants in comparison with the well-watered ones in the two seasons respectively. Plants treated with Put at 0.2 mM followed by the treatments of Put at 0.1 mM or CaCl2 at 10 mM gave the highest significant increases in soluble sugars compared to the control plants in both seasons. The treatment of Put at 0.2 mM gave a progressive improving in soluble sugars compared to the control plants under well-watered conditions in the two seasons and under stressed conditions in the first one respectively.
5. 5. Changes in leaf mineral concentrations
5. 5. 1. Nitrogen
Water-stressed plants revealed significant decreases in N% in leaf tissues compared to the well-irrigated ones in both seasons. All investigated treatments except CaCl2 at 10 mM in the second season resulted in significant increases in N% compared to the control plants in the two seasons. The treatments of Put at both examined concentrations (0.1 or 0.2 mM) gave the highest significant results in this respect. The treatments of Put at 0.1 or 0.2 mM under well-watered conditions achieved the highest significant increases in comparison to the other treatments in the two seasons.
5. 5. 2. Phosphorus
Phosphorus (P) was significantly decreased by exposing to water deficit compared to the sufficient level of irrigation. Plants treated by the high concentration of CaCl2 at 10 mM resulted in significant decrease in P% compared to the control plants in both seasons; whereas; the treatments of Put followed by AsA revealed significant increases in P% compared to the control plants in both seasons.
5. 5. 3. Potassium
Water stress resulted in significant decreases in K % compared to the well-irrigated plants in both seasons. All treatments of AsA (50, 100 ppm) or Put (0.1, 0.2 mM) improved the concentration of K% compared to the other treatments; whereas, applied CaCl2 didn’t show any significant differences with the untreated controls in both seasons. The highest significant increases were obtained by the treatment of Put at 0.2 mM in both seasons.
5. 5. 4. Calcium
Calcium-leaf concentration was decreased significantly by exposing to water deficit. Plants treated with CaCl2 especially at the higher concentration (10 mM) tended to increase leaf- Ca % compared to the other treatments in both seasons. Generally; with three exceptions of the treatment of CaCl2 at 10 mM under both level of irrigation in both seasons, the treatment of Put at 0.2 mM under well-irrigation conditions in the first season and the treatment of CaCl2 at 5 mM under drought stress in the first season; there were insignificant increases to the leaf-Ca concentration as affected by the most investigated foliar applications.
5.5.5. . Relationships between RWC and the osmolytes
An inverse significant (P= 0.0052**) relationship between RWC and proline accumulation in the leaves were detected as affected by the foliar application of CaCl2 at 5 and 10 mM under the two investigated irrigation levels. A similar trend was observed in respect to the soluble sugars (P=0.0474*). On the contrary, K and Ca had direct proportional significant (P=0.0078**; 0.0151*) relationships with RWC respectively. Similar effect was found by ascorbic acid and putrescine applications.
5. 6. Enzyme activities
5. 6. 1. Phenylalanine ammonia lyase (EC 4.3.1.24) PAL
There were significant increases in the activity of PAL in water-stressed plants compared to the well-irrigated ones in both seasons. All plants treated with CaCl2 or Put revealed significant increases in PAL activity compared to the control plants in both season; while, an opposite trend was observed in AsA-treated plants. The treatments of CaCl2 (5 or 10 mM) and Put at 0.2 mM under water shortage conditions gave the highest significant increases in PAL activity compared to the other treatments in both seasons.
5. 6. 2. Peroxidase (EC 1.11.1.7) POD
There were significant increases in the activity of POD in water-stressed plants compared to the well irrigated ones in both seasons. All foliar treatments of CaCl2 (5, 10 mM) and AsA (50. 100 ppm) caused significant increases in the activity of POD compared to the control plants in both seasons; while; the foliar treatments of Put especially at 0.2 mM inhibited significantly the activity of POD compared to the control plants in the two seasons. Under limited water supply; the treatments of CaCl2 at 10 mM in both seasons and AsA at 100 ppm in the first one respectively gave the highest significant increases in the activity of POD compared to the other treatments.
5. 7. Yield and its components
5.7.1. Seeds
All studied parameters related to the seed yield of sunflower plants and its components including head diameter (cm), head weight (g), seed weight.plant-1 (g) and seed yield (ton.fed-1) were decreased significantly by exposing to water deficit compared to those given a sufficient water supply in both seasons. All foliar treatments had distinct positive effects on the seed yield and its components of sunflower plants. In this context; the general tendency was that the highest significant (P≤0.05) increases in all investigated traits were achieved by the treatments of Put at 0.2 mM, AsA at 100 ppm and CaCl2 at 10 mM respectively compared to the control plants in both seasons. Moreover, in the first season; it was obvious that the other foliar treatments (Put at 0.1 mM, AsA at 50 ppm and CaCl2 at 5 mM) gave also increments in seed weight. plant-1 and seed yield (ton. fed -1) at the same level of significance. Under well-watered conditions the treatments of AsA at 100 ppm, Put at 0.2 mM in both seasons and AsA at 50 ppm in the first one gave the highest significant increases in head diameter (Table, 21) compared to the control plants while, under drought stress; all treatments except CaCl2 at 5 mM in both seasons and CaCl2 at 10 mM in the second one showed significant increases in head diameter. The treatment of Put at 0.2 mM achieved the highest increases in this trait compared to the other treatments in both seasons whereas; under drought stress there were significant increases by the treatments of AsA (50, 100 ppm) and Put at 0.2 mM compared to the control plants in the second season. the treatments of Put at 0.2 mM and AsA at 100 ppm achieved the highest significant values compared to the other treatments in both seasons. Under water shortage conditions all examined foliar treatments enhanced the seed weight per plant. With an only exception of the treatment of AsA at 50 ppm; these increases reached to the level of significance in the second season by all foliar treatments compared to the control plants. Total seed yield (Table, 24) was also positively affected by all investigated foliar treatments under both irrigation levels in the two seasons. In the second season; these increases reached the level of significance by all foliar treatments under water shortage conditions while; the high concentration of CaCl2 at 10 mM, AsA at 100 ppm, and Put at 0.2 mM gave the highest significant increase under the ordinary level of irrigation in this respect.
5.7.2. Oil
Water deficit caused significant decreases in seed oil percentage and total oil yield (kg. fed-1) of sunflower plants compared to those which have received adequate water supply in both seasons. The treatment of CaCl2 at 10 mM resulted in the highest significant increases in seed oil percentage compared to the other foliar treatments in both seasons. All foliar treatments revealed significant increases in the total yield of oil (kg.fed-1) compared to the control plants in both seasons. In this regard; the highest significant values were obtained by the treatment of Put at 0.2 mM and AsA at 100 ppm in both seasons. under well-watered conditions; the treatment of CaCl2 at 10 mM and Put at 0.2 mM resulted respectively in the highest significant increases in oil percentage and oil yield (kg.fed-1) in the two seasons; whereas; under water stress; in general; there was no significant differences between the most investigated foliar application and each other in this respect.
Recommendations and conclusion
It could be recommended that foliar application of Ca Cl2 and AsA as well as Put ,under water stress enhance plant growth and productivity as follows:
1- The treatments of Put at 0.2 mM, AsA at 100 ppm and CaCl2 at 10 mM achieved the highest significant values of leaves fresh weight seed weight/plant and head diameter as compared to the other treatments in both seasons
2- The increase of previous parameters reached up to 56%, 40% and 33%, respectively.
3- The treatment of CaCl2 at 10 mM resulted in the highest significant increases in seed oil percentage compared to the other foliar treatments in both seasons (reaching up to 58%)