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The field experiment was carried in the experimental farm, faculty of Agriculture, Ain Shams University, Qalubia governorate during the two winter seasons of 2012/2013 and 2013/2014 to study the response of snap bean cv Bronco to two sowing dates (1st and 16th of October) and two bio-regulators i.e., salicylic acid (SA) at 0, 0.5 and 1.0 mM and putrescine (PUT) at 0, 1.0 and 2.0 mM and the mixture between both of them.
The present investigation aimed to evaluate the response of two sowing dates and two bio-regulators of SA and putrescine and the mixture between both of them on plant growth, green pods yield components and quality and also reveal the best combination between bio-regulators and sowing date that can be recommended to increase snap bean yield under Qalubia governorate conditions.
The obtained results could be summarized as follows:
5.1. Vegetative growth:
5.1.1. Effect of sowing dates.
Sowing snap bean in the first sowing date October, 1 generally, scored the highest plant height, leaf number, leaf area and plant fresh and dry weight as compared with the second date i.e.,October,16. The results were significant, except of plant height in the first season which caused insignificant increase. Whereas, in both seasons, leaf number were statistically lacking.
5.1.2. Effect of bio-regulators.
Foliar application of SA and PUT either separately at both levels or their combination promoted all growth criteria as compared to corresponding untreated plants.
5.1.3. Effect of the interaction.
The interaction between the two tested sowing dates and the two bio-regulators spraying treatments used separately or jointly led to an increase in all values of tested growth traits. However, obtained results indicate that sowing snap bean on the beginning of October and coupling with spraying plants with the mixture of SA1 + PUT2 recorded the highest tested vegetative growth characters.
5.2. Chlorophyll content:
5.2.1. Effect of sowing dates.
Comparison between sowing dates showed that leaves of snap bean plants sown on the 1st of October recorded the higher and significant chlorophyll content compared to the second date (16th October). The results held true in both growing seasons.
5.2.2. Effect of bio-regulators.
The results show that, in both growing seasons, spraying plants with SA or PUT at the two tested rates either alone or in combination increased chlorophyll content in spite of, the individual application of the two dose rates kept at the same level of significance compared to control. The most effective and significant values recorded by SA0.5+ PUT2.0 in both growing season. Similar significant increase (only in the second season) was obtained with using higher rate of both SA1+ PUT2 compared to untreated check plants.
5.2.3. Effect of the interaction.
The higher leaf contents of chlorophyll, associated with the sowing snap bean on 1st of October combined with exogenous foliation of SA1 and PUT2 mixture.
5.3. Nutrient content:
5.3.1. Effect of sowing dates.
Comparison between sowing dates showed that the first sowing date (1st October) gave the highest significant values of N, P, K and Ca in snap bean leaves. The results held true in both growing season (except of Ca content while the effect was insignificant during first season).
5.3.2. Effect of bio-regulators.
The highest mean values of N, P, K and Ca contents were recorded in case of plants spraying with the mixture of SA1 + PUT2 compared to check and other treatments , except the P content which was highest in case of spraying with PUT1 ( lower rate,1mM).
5.3.3 Effect of the interaction.
Generally, the higher leaf contents of N, K, and Ca were associated with sowing snap bean on 1st of October, combined with exogenous foliation of SA1 + PUT2 mixture at the higher rate,i.e. .These results were significant if compared with check treatment. Whereas, the higher P content was recorded in the first and second sowing date when associated with spraying PUT solely at the lower rate in the first and second seasons, respectively.
5.4.1. Effect of sowing dates.
The higher significant value of proline content in snap bean leaves was recorded through the first sowing date i.e., 1th of October.
5.4.2. Effect of bio-regulators.
The combined application of SA1 and PUT2 mitigated and significantly enhanced the proline content in both growing seasons. Also, the combined application SA1 and PUT1 increased proline content compared with control (the results were significant only in the second season).
5.4.3. Effect of the interaction.
The results showed that, sown snap bean seeds on the 1th of October with either sole application of SA1 or the combination of SA1+PUT2 were more effective and gave the highest proline content in the first and second season respectively.
5.5. Antioxidant enzymes activity.
5.5.1. Effect of sowing dates.
The results showed that the first sowing date significantly increased the activity of POX in snap bean leaves compared with the second one .The same trend was also true for SOD while, the effect was insignificant with respect to CAT activity .
5.5.2. Effect of bio-regulators.
Foliar application of SA or PUT alone increased POX, SOD and CAT activities.
5.5.3. Effect of the interaction.
Showed that seeds sown on the 1st of October and applications of SA1 ( at the higher rate) or Put1 (at the lower rate ) singly showed the higher contents of POX in first and second season, respectively . Meanwhile, the highest significant increase in SOD and CAT were obtained by exogenous supplement with of SA1+PUT2 at the first sowing date in both seasons.
5.6. Yield and its components:
5.6.1. Effect of sowing dates
Sowing snap bean plants on 1st October significantly produced higher pod number per plant, plant yield ,total and marketable yield than sowing on 16th October.
5.6.2. Effect of bio-regulators
Application of the two tested levels of SA and PUT either separately or their combination significantly increased pod number, plant yield, total and marketable yield compared to the check untreated plants. The effective treatment in increasing pod yield were SA at higher rate (m1M) + when coupled with PUT at higher rate (2mM), followed by SA at higher rate (1mM) +PUT at lower rate (1mM).
5.6.3. Effect of the interaction
Plants growing under the first sowing date gave the greatest pod number, plant yield, total and marketable yield when combined with the mixture of SA1 + PUT2.
5.7 Pod quality:
5.7.1. Pod weight, length and thickness.
184.108.40.206. Effect of sowing dates.
Sowing snap bean seeds on the 1st October was the better proper sowing date giving the heavier pod weight. Data also indicated that pod length and thickness did not vary significantly in the two seasons due to sowing dates.
220.127.116.11. Effect of bio-regulators.
Foliar application of either SA or PUT alone at any tested concentration or its combinations increased the length and thickness of pod as compared to check treatment.
18.104.22.168. Effect of the interaction.
Seeds sowing on the 1st of October and sprayed with water (check treatment) and PUT1 yielded the highest pod fresh weight in the first and second season , respectively . Concerning the pod length, it was found that seeds sown on the 16th of October and sprayed with SA1+ PUT2 in the first season and seeds sown on the 1st of October and sprayed with SA0.5+ PUT2 in the second season recorded the highest pod length. While, the interaction between sowing dates and bio-regulators did not have any significant influence on pod thickness, in both seasons.
6.8. Chemical composition of green pods:
6.8. 1. Protein percentage.
6.8. 1.1. Effect of sowing dates.
Showed that, sown snap bean seeds on the 1st of October scored the higher percentage of protein in green pods in both seasons.
6.8. 1.2. Effect of bio-regulators.
Showed that, foliar application of either SA or PUT at any concentration as well as their combination increased protein percentage as compared to the respective control with clear superiority to SA1 + PUT2 treatment.
6.8. 1.3. Effect of the interaction.
Sowing date on the 1st of October and spraying with SA1+PUT2 led to the highest protein content.
6.8. 2. Vitamin C content.
6.8. 2.1. Effect of sowing dates.
Vitamin C occurred in plants sown their seeds in the 1st of October with strong downward trend relative to the later the sowing date (16th October),
6.8. 2.2. Effect of bio-regulators.
Foliar application of either SA or PUT at any concentration or combined significantly increased VC content as compared to check treatment (except of PUT1 which was statistically equal to that of the control in second season). The combination of SA1 + PUT2 led to the highest percentage of VC in green pods in both season.
6.8. 2.3. Effect of the interaction.
The interaction between sowing dates and spraying treatments indicated that the interaction between the 1st of October and the combination of SA1and PUT2 had the highest values of VC content in both seasons.
6.9. 3. Fiber percentage.
6.9. 3.1. Effect of sowing dates.
Significant higher percentage of fiber was obtained in pod of snap bean sown their seeds on the 1st of October, this trend was showed at both seasons of growth.
6.9. 3.2. Effect of bio-regulators.
Application of SA1 + PUT2 treatment led to the highest percentage of fiber in green pods in both season.
6.9. 3.3. Effect of the interaction.
The interaction between SA1+PUT2 and the 1st of October led to the highest fiber percentage in both growing seasons.