Extreme variations during hot summers cause damage to the intermolecular interactions needed
for proper growth, thus impairing plant development. Temperature variations occur naturally
during the growth of plants. In this study, irrespective of the mulberry varieties, the
photosynthetic rate was considerably decreased under high-temperature stress. Closure of
stomata is a common heat-induced feature in many crops. When the mulberry plants were
exposed to high-temperature stress of 40º C stomatal conductance was considerably decreased.
Greater reduction was observed in G2 and G4 at both 7 th and 14 th day after stress. The percent
reduction in G4 at the 14 th day after stress was 52.2% and G2 at 14 th day after stress was 52.63%
with the values 0.19 cm s -1 and 0.18 cm s -1 . Similarly, the Transpiration rate has significant
impact on the physiological and biochemical processes of the plant system because it alters the
leaf temperature which in turn affect many processes. The varieties G2 and G4 showed lower
transpiration rates under stress conditions, whereas, the variety V1 recorded higher transpiration
rates when exposed to 40ºC. The chlorophyll stability index on the 14 th day after stress showed
that the variety V1 recorded the highest of 79.85% followed by MR2 at 75.64% and S36 at
69.75%.