In this study, the physiological and molecular defects leading to growth reduction under salt stress in

Egyptian clover (Trifolium alexandrinum L.) were investigated. Time-course response of growth to salt

stress with 200mMNa+ and/or Cl− showed that significant reduction in the growth of the stressed plants

was delayed until the sixth day of stress indicating that the plant is more resistant to the osmotic component

of salt stress. The rate of photosynthesis started to decrease significantly from the third day of stress

although the rate of transpiration decreased to 18.4% of the control after 2 h indicating that reduction

in photosynthetic rate may have not been essentially due to CO2 limitation. The mutual relationships

of photosynthesis and growth are discussed and evidence is provided that growth reduction is largely

a consequence rather than a cause of inhibition of photosynthesis. Data also shows that inhibition of

photosynthesis could have resulted from excessive accumulation of Na+ in the leaves along with downregulation

of Na+-sequestering genes (NHX1, H+-PPase and H+-ATPase) that may have led to loss of the

efficiency of Na+ sequestration into the vacuole and subsequent damage to photosynthesis. The role of

HRD gene in regulating transpiration is discussed.