Abstract
This study investigated the effect of high day temperature (30 to 35°C for 5 h from 10: 00 h to 15: 00 h) for 5, 10 and 20 days at different developmental stages of inflorescence on the abortion in Gymnaster savatieri Kitamura.
The plants were exposed to high temperature during the following eight developmental stages of inflorescence: 1) early stage of floret formation, 2) middle stage of floret formation, 3) early stage of petal formation, 4) middle stage of petal formation, 5) late stage of petal formation, 6) complete stage of petal formation, 7) budding stage, 8) 7 to 10 days after budding.
The occurrence of blindness (characterized by necrotic disk and ray florets) was high (70-100%) when exposed to high temperature treatment for 20 days from the early stage of floret formation to the middle stage of petal formation. Also, from the early stage of floret formation to the early stage of petal formation, the percentage of blindness was 60 to 85% even after 5 days of exposure to high temperature occurred after complete petal formation.
The entire necrosis of disk florets (characterized by necrotic disk florets and undeveloped ray florets) was 10% when exposed to high temperature for 10 and 20 days at the late stage of petal formation and for 20 days at the complete stage of petal formation.
The partial necrosis of disk florets (characterized by necrotic central disk florets and welldeveloped ray florets) occurred from the late stage of petal formation to budding stage, and this percentage was high when exposed for 10 and 20 days at the complete stage of petal formation. However, no partial necrosis of disk florets occurred 7-10 days after budding, even when the plants experienced high temperature for 10 and 20 days.
