*4.4. Anatomical Characteristics*

The present experimental results (Figures 8 and 9a–c) clear that foliar application with salicylic acid at 3 mM on faba been plant led to the highest increase in the thickness of the upper, lower epidermis, leaf blade thickness, palisade, or spongy tissue midrib zone, length, and width of the vascular bundle and. Also, foliar application with salicylic acid produced great increase in the most mentioned layers more than the control. Although the foliar application with all treatments led to a slight increase in the thickness of the examined layers was recorded especially by benzoic acid, compared to the untreated plants. In this regard, Ali et al. [71] on maize (*Zea mays*, L.) reported that treatment with citric acid led to increasing the upper and lower epidermal layers, length of the vascular bundle, and mesophyllic tissue, while the width of vascular bundle was similar to the control. Concerning foliar application with salicylic acid, the results showed an increase of thickness in both palisade and spongy tissues; these results are in agreement with Gomaa et al. [18], who observed that foliar spraying of the cultivar 'Giza 2, Egyptian lupine, with salicylic acid increased the thickness of leaflets lamina and midvein. This is due to an increase in the thickness of spongy and palisade tissues as well as to increase in the midvein bundle size. Some investigators confirmed the present findings using salicylic acid on other field crop plants, for instance, Cárcamo et al. [16] on *Zea mays*, L., Nour, et al. [17] on bean, Gomaa et al. [18] on *Lupinus termis* L. and Khalil, et al. [72] on pea plants. They found that salicylic acid application increased the thickness of the midvein and lamina of the studied plant leaves. Also, Maddah et al. [73] found that spraying salicylic acid with 0.1 mM increased the stomata number, but watering plants with 1.5 mM of salicylic acid damages the parenchyma tissues in leaves, the tissue of sclerenchyma in stems, and

xylem in the root, the exogenous spraying of SA might alleviate the inhibitory impact of salinity stress on the growth, physiological and anatomical features, and the productivity of cowpea plants El-Taher et al. [74].
