Articles
USE OF LIGHT, CARBON DIOXIDE ENRICHMENT AND GROWTH REGULATORS IN THE OVERWINTERING OF HARDY ORNAMENTAL NURSERY STOCK CUTTINGS
Dusk-to-dawn, low intensity lighting increased budbreak and leaf retention in Betula pendula cuttings and gave larger, leafier plants than unlit controls.
Additional CO2 enrichment improved growth further and gave plants twice the size of controls by mid-season of the following year.
Overwinter survival of the rooted cuttings was greatly enhanced by the light and light + CO2 treatments.
In a third treatment, eight weekly sprays of 100 ppm2 gibberellic acid (GA3) promoted irregular budbreak in rooted cuttings, but produced only weak growth and marginally improved overwinter survival.
In Berberis thunbergii ‘Atropurpurea rosea’ cuttings, only the GA3 treatment promoted budbreak but the breaks were irregular and the shoots etiolated in appearance.
GA3 increased flowering in both Berberis and Betula cuttings but treated Berberis plants broke bud late in the following spring and grew poorly.
Light and light + CO2 gave modest improvements in overwinter survival and subsequent growth.
Responses to extended photoperiod and GA3 sprays were closely similar in rooted cuttings of deciduous hybrid azaleas and in Acer saccharinum, but GA3 was less effective in Cornus alba ‘Spaethii’ and both treatments produced undesirably weak growth in Weigela florida ‘Variegata’.
Growth retarding chemicals and antiauxins were incorporated with GA3 sprays in an attempt to reduce the "etiolation" effects observed in some species.
Tri-iodobenzoic acid (TIBA) and B9 (N-Dimethylaminosuccinamic acid) were partially effective with Spiraea bumalda ‘Coccinea’, but in Acer saccharinum, Phosfon, B9, TIBA and para-hydroxybenzoic acid increased rather than reduced the GA3-induced height growth.
In attempts to improve the elongate growth form of GA3 treated cuttings, kinetin (6-Furfurylaminopurine) promoted additional breaking and growth of lateral buds in both Cornus and Weigela.