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L-ascorbic acid (AsA) known as vitamin C, which is an important

antioxidant in both plants and animals (Akram et al., 2017). AsA has

different roles in the plant such as regulating cell division and

expansion, plant growth and development, and improving plant

tolerance to biotic and abiotic stresses (Kka, 2017). Under stress

conditions, excess reactive oxygen species (ROS) accumulate in plants,

causing significant damage to plants and obstructing natural

physiological activities in plants (Zhao et al., 2018). However, it was

found that the subcellular level and exogenous application of ascorbate

partially functions as a defence mechanism in the plant (Figure 1)

Introduction

Objective

Results

Soaking onion sets into AsA for 24 h prior planting influenced on the growth of green onion

remarkably. Root intensity was higher in the plants treated with 2.5 mM AsA (Figure 5 a). The 2.5

mM AsA treatment statistically increased the root weight per plant (Figure 5 b). In the similar way,

root length, plant height and bulb diameter increased by 2.5 mM AsA treatment but no statistical

differences was found when compared to the control (Figure 5 c, d and e). Onion sets treated with

5mM AsA was adversely affected on the growth of green onions (Figure 5).

Conclusion

Figure 4. Temperature and rainfall amount during growing season (November 2018 to March 2019) in Erbil. (A) Maximum, Minimum

and average temperature (°C). (B) Average rainfall amount and rainy days.

The experiment was conducted at the Grdarash research

center; College of Agriculture. The land was tilled and

divided into 12 experimental units (1×1) m2 (Figure 2).

Uniform onion (local white cultivar) sets were soaked in AsA

solutions (0, 2.5 and 5 mM) for 24 hours at 4°C (Figure 3).

The sets were planted at 5cm depth and 15 cm apart. The

experiment was conducted during the rainy and cold season

(November 2018 – March 2019) (Figure 4). No agricultural

practices were applied during the growing season.

The fresh weight of roots, root length, plant height and the

bulb diameter were measured manually and collected at the

end of the experiment (April 5, 2019).

Department of Horticulture, College of Agriculture, Salahaddin University, Erbil

agho03015@student.su.edu.krd

Balkies Shekho, Noura Kka

Impact of exogenous ascorbic acid on the growth of green onions under changed climate

Figure 1: Summary of the ROS

cycle that operates in plants during

biotic and abiotic stresses.

The research was conducted to understand how AsA improves plant defense mechanisms against

environmental stresses.

Materials and methods

Green onions (Allium cepa L.) are gaining popularity in the Iraq market because of their mild flavor.

This type of onion, also known as salad onions, spring onions, or green bunch onions, is harvested in

the immature stage before the bulb has fully developed.

The optimal temperature for growing onions is between 20° to 25°C. Green onions are shallow-rooted

and grow in a wide range of soil types. Green onion development requires frequent and uniform

irrigation. The amount and frequency of irrigation depends on the soil type, weather conditions, and

development stage of the crop.

This research provides a basic understanding of the critical role that AsA plays in plant growth and

development. The experimental data presented in this research suggests that AsA is certainly

important for improving plant tolerance to biotic stresses. The 2.5 mM AsA was found to be more

effective in increasing the root intensity and weight of the green onions subjected to changing the

climate.

References Akram, N. A., Shafiq, F., & Ashraf, M. (2017). Ascorbic acid-a potential oxidant scavenger and its

role in plant development and abiotic stress tolerance. Frontiers in plant science, 8, 613.

Kka, N. M. E. (2017). Plant ascorbate influence on cell division, growth and seed production of

Arabidopsis thaliana. PhD dissertation. Deakin University.

Wang, Y., Zhao, H., Qin, H., Li, Z., Liu, H., Wang, J., & Zhang, Z. (2018). The Synthesis of Ascorbic

Acid in Rice Roots Plays an Important Role in the Salt Tolerance of Rice by Scavenging

ROS. International journal of molecular sciences, 19 (11), 3347.

Figure 5. The influence of exogenous application of AsA on green onions growth and development. (A) Representative picture of green

onions exposed to different concentrations of AsA. (B) Root weight (mg) per plant of green onions. (C) Root length (cm) per plant. (D)

Plant length (cm ) per plant. (E) Bulb diameter (cm) per plant.

Experimental design and statistical analysis

Randomize complete block design was followed with four replicates. Data were analyzed using SPSS

software. Duncan test was used to compare the treatments means at a level of significant 0.05.

Figure 2. Layout of the field experiment.

Figure 3. Soaked onion sets in AsA solutions.