Leaf area, xylem cycling and Ca status in apples.
Lang, A.; Volz, R. K.;
Acta Horticulturae Year: 1993 Issue: No. 343 Pages: 89-91 Ref: 7 ref.
1993
บทคัดย่อ
Low Ca concentrations at harvest predispose apple fruits to physiological disorders during storage and advance fruit senescence. Ca is known to move exclusively in the xylem system and this study was carried out to investigate the possibility that the effect of nearby leaves on fruit Ca nutrition is linked to the xylem reversal patterns. Spur clusters on mature Royal Gala apple trees were thinned at bloom to a single flower, and the bourse shoot and all but 1-2 spur leaves were removed from half of the spur clusters. Xylem sap exchange between tree and fruit was measured 8 weeks later. Fruits were then harvested and bourse + spur leaf areas, fruit fresh weights and Ca contents were determined. Fruit Ca concentration was significantly reduced by leaf removal but fruit size was not affected. There was considerable day-to-day variation in the amounts of sap exchanged between tree and fruit. Outflow from the fruit generally occurred during the day and inflow during the night. Volumes of xylem sap exchanged were influenced strongly by spur + bourse leaf area. Defoliation significantly reduced both outflow (by 25%) and inflow (by 30%). Spur wood xylem sap had 10 times the concentration of Ca compared with fruit xylem sap, therefore, much less Ca leaves the fruit in the outflowing sap than enters it in the inflowing sap. Factors which stimulate foliar transpiration (and increase volume of sap exchange) should also increase Ca levels and thus improve fruit quality.