Pollen viability and storage life in Leonurus cardiaca L.

• The best time to use the pollens of Leonurus cardiaca is 1–2 h after anthesis.
• The low storage temperature could significantly prolong the storage time of pollen of L. cardiaca.
• At −80 °C, pollen viability could be maintained for 60 days.

Leonurus cardiaca (Lamiaceae) is an important medicinal plant growing in many regions of Iran. It has been used to cure cardiovascular diseases, stress, anxiety, and nervous irritability. There has been no report on the pollen biology of this species. Therefore, this experiment was designed to investigate viability, in vitro germination, optimal storage temperature, and storage life of the pollen grains. Two colorimetric methods using either 2,3,5-triphenyl tetrazolium chloride (TTC) or acetocarmine were employed. In a medium containing 5% sucrose, 100 ppm boric acid (H3BO3), and 1% agar, pollen germination rate was examined at five developmental stages including one day before anthesis, and 2 h, 24 h, 48 h, and 72 h after anthesis. Four storage temperatures, 4, 25, −20, and −80 °C, were applied to determine the optimum storage temperature and storage life of the pollens. Pollen germination was tested in a culture medium at 5-day intervals for 4 and 25 °C and every month for −20 and −80 °C. The highest pollen viability was observed by acetocarmine method. The viability of pollens before anthesis was 91.35% and reduced to 2.06% 72 h after anthesis. The highest germination was achieved in pollens gathered 2 h after anthesis (82.84%), which reduced to 0.19% 72 h after anthesis. Pollen germination was stopped after 20, 50, 60, and 60 days of storage at 25, 4, −20, and −80 °C, respectively.

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