Growth and Development of Horticultural Crops (1+1)

Introduction-Ethylene

• Neljubow in 1901 identified ethylene in laboratory air from illuminating coal gas which caused typical symptoms in etiolated pea seedlings grown in dark in the lab, viz., (i) inhibition of stem elongation, (ii) stimulation of radial swelling of stems and (iii) horizontal growth of stems with respect to gravity.
  
• These symptoms were later termed as ‘triple response’ and were not observed in etiolated pea seedlings grown in normal air free from coal gas.
• Gane (1934) clearly established that ethylene is actually a natural product of ripening fruits and is responsible for hastening ripening process. Meanwhile, several other experimenters found evidence of ethylene being produced not only by ripening fruits but also by flowers, seeds, leaves and even roots and having profound regulatory activity in plants.
  
• The importance of ethylene as hormonal regulator of physiological processes was realized only after the advent of gas chromatography (GC) and its use in ethylene research, (Burg and Thimann, 1959, 60). Soon, this was followed by an avalanche of experimental research work on ethylene and finally ethylene emerged as an accepted natural plant growth hormone (Pratt and Goeschal, 1969).