RELATIONSHIP BETWEEN COLEOPTILE ELONGATION AND ALCOHOLIC FERMENTATIONIN RICE EXPOSED TO ANOXIA .1. IMPORTANCE OF TREATMENT CONDITIONS AND DIFFERENT TISSUES

The relationship between coleopile elongation and alcoholic fermentati on of rice under anoxia is examined using seeds either: (a) N-2 flushe d during submergence, (b) incubated in stagnant deoxygenated agar at 0 .1 % w/v to simulate the stagnant conditions of waterlogged soil, or ( c) incubated in waterlogged soil. Coleoptile elongation growth was gre ater for N-2 flushing > stagnant agar > soil; seed survival was also g reatest in this order over 1-5 d. Ethanol concentrations in coleoptile s and intact seeds (cv. IR42) were approximately 300 and 100 mol m(-3) respectively when seeds were grown 3 d in stagnant agar, however 92 % of the ethanol in seeds diffused into the external medium when soluti ons were mixed for 5-10 s. Coleoptile growth under anoxia was related to rates of ethanol synthesis (R(E)) in different treatments; there wa s greater coleoptile growth and R(E) for seeds in N-2 flushed solution s than in stagnant deoxygenated agar. Coleoptile growth of individual seeds was also related to the R(E) of each seed at 2-3 d after anoxia (r(2) = 0.46). Analysis of different tissues was important in evaluati ng growth and metabolism of coleoptiles. Although the coleoptile only accounted for 0.7 % of seed dry weight at 3 d after anoxia, it contain ed 21 % of the ethanol produced by rice seeds. There were also three-f old higher rates of R(E) on a fresh weight basis in expanding tissues in the base of the coleoptile relative to the elongated tissues at the apex. Results are discussed in terms of the importance of environment al conditions used to impose anoxia, quantification of R(E) in specifi c tissues and the possibility that under stagnant conditions high etha nol concentrations in tissues may limit R(E) and coleoptile growth.