In vitro flowering and production of viable pollen of cucumber

Flowers were produced on sterile cucumber (Cucumis sativus L.) plants grown in vitro from seed and micropropagated shoots from stem fragments. The highest numbers of flowers on plants from both sources were produced on Murashige and Skoog (MS) medium without plant growth regulators (PGR), as well as with 6 mu M of kinetin (Kin). Plants cultured on MS medium supplemented with 8.9 mu M benzyladenine (BA) and 1.1 mu M 1-naphthaleneacetic acid (NAA) did not flower. In vitro grown plants produced fewer, smaller flowers compared with greenhouse-grown plants. Male and female flowers developed on plants grown in vitro from seed and were morphologically similar to flowers on greenhouse grown plants. Micropropagated shoots produced male flowers with altered morphology. The highest viability (72.9 +/- A 4.2%) and germination (69.5 +/- A 4.1%) of pollen were observed for plants grown from seed on MS medium supplemented with 6 mu M Kin. Cytological observations of meiosis in anthers of male flowers from in vitro grown plants revealed abnormalities, such as monads, dyads, triads, polyads, microcytes and degeneration of tetrads, causing reduced viability and germination of pollen. The fewest meiotic irregularities in pollen mother cells were observed in plants grown on MS medium that was PGR-free (12.1 +/- A 0.9%) or with 6 mu M Kin (20.9 +/- A 1.7%).