The effects of exogenous silicon (Si) on salt (NaCl)-stressed borage (Borago officinalis L.) plants were investigated in this study. Six levels of Si (0, 0.5, 1, 1.5, 2, 2.5 mM) and two levels of NaCl (0 and 120 mM) were applied to study the effect of NaCl and Si on some physiological, biochemical and anatomical properties of Borago officinalis L. Salt stress reduced fresh and dry weight, protein contents and catalase activity. In contrast, proline, glycine betaine, malondialdehyde and activity of superoxide dismutase and ascorbate peroxidase increased in salt-stressed plants. The results of anatomical study of leaf cross section showed that salt stress resulted in noticeable anatomical variations such as increase in thickness of leaf blade and thickness of palisade parenchyma cells. Other interesting variations in salt stress include changes in structure and numbers of trichome and stomata. Si treatment in comparison with the plants only treated with salt resulted in an improvement in the studied physiological parameters, especially at 1.5 mM level. Also, Si treatment could moderate the negative effects of salt treatment on the studied anatomical attributes.

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In this research, the effect of salinity on the development of anther in hydroponically-grown borage was studied. Plants grown on hydroponic media are rapidly and transiently stressed. The overall objective of this research was to elucidate the microscopic effects of salinity on the formation, development, and structure of anthers. Flowers, at different developmental stages, were removed, fixed in FAA, embedded in paraffin, and cut into 7-10 μm slices using a microtome. Staining was carried out with Hematoxylin-Eosine, and the developmental stages of the control and NaCl-treated plants were compared. In control plants young anther consisted of 4 pollen sacs. Anther wall development followed the typical dicotyledonous pattern and was composed of an epidermal layer, an endothecium layer, and the tapetum. Microspore tetrads were tetrahedral. Salinity caused certain abnormalities during pollen developmental processes, such as the destruction of the anther wall and both the degeneration and production of abnormal pollen grains. A decrease in plant fecundity, which involves aborting pollen, followed by a change in resource from reproductive activities to metabolic reactions is possibly a general response to the deleterious effects of salinity.