Effects of light and ethephon on germination of light-inhibited Amaranthus hypochondriacus seeds in relation to the respiration, stored nutrients and certain enzymatic activities

Physiology in seed germination of Amaranthus hypochondriacus known as both ornamental and summer vegetable crop was studied in relation to elucidation and characterization of the respiratory and relevant enzymatic changes taking place in the germination of seed. Dark, red light ethephon in the light and ethephon plus red light treatments showed four stages of oxygen uptake in the germination, namely, first increase in oxygen uptake, steady continuation of the uptake, the rapid increase in the uptake, and the decrease in the uptake. There were no such distinguishable stages for seed placed in the light. Although carbohydrate and protein content, 6 hours after the seed sowing, did not show any change, there was however considerable decrease in the content due largely to the consumption of the seed content if allowed to germinate in both the dark and ethephon, red light alone, and combination between ethephon and red light. There was considerable decrease in the content due to the consumption of the seed content if allowed to germinate in both the dark and ethephon in the light alone, and ethephon plus red light treatment in combination. There was a gradual decrease in the content of total sugar in the light, whereas a rapid decrease was noted in both the dark and the ethephon and red light treatments, as the respiration was expedited. Reducing sugar and amino acid content did not show a change in the light, whereas they were increased since the dark and ethephon plus red light treatments caused a promotion in decomposition of carbohydrate and protein both in the dark and in the treatment with ethephon and red light. Enzymes involved in the respiration as hexokinase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were not distinguishably activated at the critical time in the light, and thus seeds did not germinate. These enzymatic activities on the contrary were promoted when either the dark or ethephon in the light or/ and red light were provided to seeds