15. Response of the Photosynthetic Apparatus and Male Gametophyte of Pepper Plants (Capsicum annuum L.) to Various High Temperature Regimes

The changes in chlorophyll fluorescence parameters and in male gametophyte caused by high temperature (HT) were studied to determine a suitable regime to test the heat tolerance of Capsicum annuum genotypes. The plants (cv. Bial Kalinkov) were grown in a glasshouse in 5 L plastic pots on a commercial soil-peat substrate. Whole plants were treated with HT (35o, 40o and 45oC for 1, 2, 3, and 4 hours) in the bud formation-blossoming stage. It was established that the applied HT regimes influenced the pepper plants to varying extent. We concluded that: temperature values of 35oC and 45oC are not suitable to screen test pepper lines and varieties to heat tolerance; the male gamethophyte is more sensitive to HT stress compared with the photosynthetic apparatus; a semi-lethal effect on the male gamethophyte of pepper plants from the model cv. Bial Kalinkov was manifested at 40oC for 2 and 3 hours; the changes of the chlorophyll fluorescence parameters are better expressed at the higher values of HT regimes (40oC and 45oC for 2 and 3 hours); a suitable temperature regime to screen-test the heat tolerance of pepper species includes 40oC and duration of 2 or 3 hours.