Effect of sowing dates and vernalization on Beta vulgaris L. cv. Univers C-leaf structure.

This research was conducted to study the effect of three different sowing dates (15th October, 15th November and 15th December) and two vernalization treatments (5 °C and -20 °C) on leaf structure of Beta vulgaris L. cv. Univers. The obtained data are summarized as follows: The maximum values of the most studied parameters; lower epidermis + spongy tissue thickness, midrib, mesophyll tissue, vascular bundle, collenchymatous tissue and number of xylem vessels per arm were found as a result of 15th October sowing date treatment compared with the two other sowing dates. Furthermore, effect of the cooling treatments varied according to the recorded character, sowing date and cooling degree. Most of the vernalization treatments at early sowing dates increased the mesophyll tissue, midrib, number of vascular bundles per transverse section, vascular bundle thickness and number of xylem arms per transverse section. The two studied cooling treatments at 15th October sowing date increased both stomatal index and average number of stomata: average number of epidermis cells compared with the control. Furthermore, 15th October under -20 °C treatment led to small epidermal cells and stomata formation, straight epidermal cell walls and closed stomata in comparison to the control.