Abstract
This experiment was conducted to study the combined effect of high temperature and shading on the flower bud abortion in Gymnaster savatieri Kitamura. The temperature treatments ranged from 30 to 35°C for 5 h from 10 am to 3 pm, for 0, 5, 10 and 15 days and shading was provided with two layers of black cheese cloth for 0, 5, 10 and 15 days. Their effect at eight specific developmental stages of inflorescence was considered.
The abortion occurred from the early stage of floret formation to the budding stage. No abortion occurred 7 to 10 days after budding. The percentage of the abortion increased with the duration of high temperature and shading. Also, the percentage of the abortion became less as the developmental stages of inflorescence advanced.
The occurrence of blindness (characterized by necrotic disk and ray florets) was severe from the early stage of floret formation to the middle stage of petal formation. The percentage of the blindness increased with the duration of high temperature and shading.
The entire necrosis of disk florets (characterized by necrotic disk florets and undeveloped ray florets) occurred at the late stage of petal formation and the complete stage of petal formation. The percentage was high at high temperature and shading for 15 days.
The partial necrosis of disk florets (characterized by necrotic central disk florets and welldeveloped ray florets) occurred from the late and complete stages of petal formation. The percentage was higher at the complete stage of petal formation. Also, the percentage of the partial necrosis of disk florets increased with the duration of high temperature and shading. But, shading alone, without high temperature, did not induce partial necrosis of disk florets even when the duration of shading was increased.
