Two field experiments were carried out during the summer seasons of 2014 and 2015 at the Experimental
Farm of the Faculty of Environmental Agricultural Sciences, El-Arish, Arish University, North Sinai Governorate,
Egypt to improve the performance of tomato plants (Hybrid Alissa F1) grown under high temperature. This study
included 12 treatments which were the combination between application of two types of floating covers (bare plants,
covering with Agryl) and spraying with some growth substances to improve the fruit setting under heat stress (control,
Ca+B, GA3, IAA, GA3+Ca+B, IAA+Ca+B); Ca, B, GA3, and IAA were used at 500, 25, 20 and 20 ppm, respectively.
The results showed that tomato plant growth (both of fresh weight and dry weight) proline concentration, and fruit
setting were increased with application of floating cover (Agryl), while total chlorophyll content, marketable yield per
plant and per feddan, total yield/fed. and number of seeds/fruit were decreased. Spraying with IAA,GA3+Ca+B and
IAA+Ca+B were the best treatments for total dry weight, total chlorophyll, proline and fruit setting while IAA+Ca+B
was the best treatment for both marketable yield /plant and per fed., total yield/fed. as well as number of seeds/fed. The
best interaction treatments for total chlorophyll, the components of marketable yield and number of seeds/fruit were
spraying bare plantswithGA3+Ca+Bor IAA+Ca+B, while the same treatments under floating cover increased proline
concentration in leaves and partially increased average fruit setting (%).