In order to determine the date of initiation and emergence of sugarcane inflorescences, samples from cultivars NA 56-79, SP 70-1143 and IAC 52-150 were collected from field trials conducted in Piracicaba region. Shoot apices from 10 vigorous stalks, from each cultivars, were collected once each week from February 20th to July 3rd, 1984. Floral differentiation and development were analyzed by microscopic examination of median longitudinal sections of shoot apices, as well as measurements of length of inflorescences. During the critical period of induction - from February 25th to March 20th - all climatic data were collected at the Piracicaba Experimental Station of the Instituto Agronômico in the same climatological area. Temperatures higher than 31°C, low rainfall, 47,3mm, and the high percentage (76%) of days with more than 13°C difference between maximum and minimum temperatures during the critical period of induction, affected the floral differentiation. The cultivars NA 56-59 and SP 70-1143 did not flower while the cultivars IAC 52-50 flowered only 50%. The earlier recognizable inflorescence primordia was detected on April 6th, when the dometype structure measured 0.011cm, and the emergence panicle occurred during the first week of July.
sugarcane; Saccharum spp.; floral initiation; climatic factors