The influence of exogenous ethylene on growth and photosynthesis of mustard (Brassica juncea) following defoliation

Mustard (Brassica juncea L.) plant is characterized by a large number of broad leaves in the lower layers. These leaves remain below light compensation photosynthetic point and abscise at maturity. An experiment was conducted to find out the effect of early removal of such leaves on the growth of the plant, on assimilate balance and any association of growth with changes in ethylene level. Intact plants and plants with 50% of total leaves from lower-half axis of the plant removed after 40 d after sowing were compared. Removal of 50% lower leaves increased the emergence of new leaves, leaf area, plant dry mass, carbonic anhydrase (CA) activity and photosynthetic rate (PN). Ethephon at 200 μl l−1 increased the overall growth of the plants in no-defoliation treatment, which was equivalent to the defoliation plants treated with water spray. Ethephon spray on defoliated plants proved inhibitory. The ethylene level in 200 μl l−1 ethephon treatment on no-defoliated plants was equal to water spray on defoliated plants. The results suggest that there exists a correlation between defoliation, ethylene and growth of plants.