조생 온주밀감의 과실발육 중 건조 스트레스 시기가 과즙의 당 농도와 당 관련 효소 활성에 미치는 영향

Sixteen uniform potted 7-year-old ‘Okitsu Wase’ satsuma mandarin (Citrus unshiu Marc.) grafted on trifoliate orange stock in a glass house were randomly assigned to four groups; conventional soil water supply at level of Ψ max of -0.3~-0.4 ㎫ during the whole period from July 21 (fruit diameter about 30㎜) through Nov. 20 (WW), mild drought stress at level of Ψ max of -0.6~-0.7 ㎫ during the whole period (DD), drought stress during 50 days from July 21 through Sept. 10 (DW), and drought stress during 50 days from Oct. 1 through Nov. 20 (WD). Drought stress inhibited the fruit growth, but the growth became most vigorous in response to supply of water after drought, resulting in the largest fruit in DW. The concentration of fructose and glucose in fruit juice was increased by drought stress, and the difference between fruits with and without stress did not changed during the prolonged drought, but disappeared in response to supply of water after drought. The concentration of sucrose was also increased by drought, but the difference between fruits with and without stress steadily increased during the prolonged drought and maintained even under the condition without drought. The activity of sucrose synthase (SS) and sucrose phosphate synthase (SPS) was increased by drought, and the pattern of change was similar to that of fructose or glucose rather than that of sucrose. It was suggested that the increase in the activity of SS by drought represents the increase in sink strength, the increase in the concentration of hexoses accounts for the degree of active osmoregulation, and the accumulation of sucrose is the accumulated results of the increased sink strength.