Root and Stem Extension of Young Papaya Plants

Abstract

`Red Lady' and `Tainung #1' papaya plants were grown in nursery trays with cells 5.1 cm in diameter. After 10 weeks, mean height of the `Red Lady' plants was 10.1 cm and that of the `Tainung #1' plants was 9.3 cm. Each of five plants per cultivar was planted between two root observation windows, one at 45 cm and the other at 95 cm. Roots reached the 45-cm observation window in 30 days, when mean height of the `Red Lady' plants was 18.7 cm and that of the `Tainung #1' plants was 13.0 cm. Roots reached the 95-cm observation window in 55 days, when mean height of the `Red Lady' plants was 55.4 cm and that of the `Tainung #1' plants was 40.6 cm. Thus, root extension during these initial 55 days was 17 to 18 mm per day for both cultivars, and stem extension during this period was 8.7 mm·d–1 for `Red Lady' and 5.5 mm per day for `Tainung #1'. Root extension declined for both cultivars to ≈12 mm·d–1 by the initial bloom period, then further declined to ≈4 mm·d–1 during and after the initial fruit set stage. Stem extension increased to about 19 mm·d–1 after the plants were established and remained at this rate until well into the stage of heavy fruit set and growth, when it declined to about 8 mm·d–1. The amount of fruit set influenced root characteristics more than cultivar.