Photosynthetic daily light integral during vegetative propagation and finish stages influence growth and development of annual bedding plant species

Veronica Ann Hutchinson, Purdue University

Abstract

Vegetative propagation of annual bedding plants typically occurs during the late winter and early spring when ambient photosynthetic daily light integral (DLI) is low, especially in the northern United States. Vegetative cuttings are produced in two phases: a young plant stage, in which shoot-tip cuttings are rooted as liners, and a finish plant stage, in which the liners are transplanted into larger containers and grown until marketable. Previous studies have shown that DLI during the propagation (PDLI) or finish stage (FDLI) influences morphological characteristics in a number of ornamental crops. The objectives of this study were to: 1) quantify how PDLI influences subsequent growth and development of Angelonia angustifolia Benth. 'AngelMist White Cloud' (angelonia), Nemesia fruticans (Thunb.) Benth. 'Aromatica Royal' (nemesia), Osteospermum ecklonis (DC.) Norl. 'Voltage Yellow' (osteospermum), and Verbena Ruiz × hybrida 'Aztec Violet' (verbena) (Expt. 1); 2) quantify the effects and interactions of PDLI and FDLI on growth and development of these species (Expt. 2); and 3) to determine if species and cultivars of angelonia and nemesia vary in their response to PDLI (Expt. 3). Cuttings were propagated in a glass-glazed greenhouse with an air and substrate temperature set point of 22 and 23 °C, respectively. After callusing (providing DLI of about mol·m -2·d-1 for 7 d), cuttings were transferred to PDLI (about 1 to 17 mol·m-2·d-1) treatments for 14 d. For Expts. 1 and 3 FDLI was maintained at about 12 mol·m -2·d-1 during finishing to identify any residual effects of PDLI. For Expt. 2, plants were finished under a wider range of FDLIs (about 1 to 17 mol·m-2·d-1). As PDLI increased, time to first open flower (TTF) decreased for all four species. For example, TTF for angelonia and osteospermum was reduced by 23 and 19 d, respectively, as PDLI increased from 1 to 12 mol·m -2·d-1. Additionally, as PDLI and FDLI increased, TTF decreased for all species. For example, an increase in PDLI and FDLI from about 2 to 17 mol·m-2·d-1 resulted in a 46 d decrease in TTF for nemesia. Total dry mass increased as both PDLI and FDLI increased for angelonia, nemesia, osteospermum, and verbena. However, variation in branch number, height, root to shoot ratio, and node number among species was observed in response to increasing PDLI and FDLI. Time to flower for most cultivars of angelonia and most cultivars and species of nemesia responded similarly to PDLI. Increasing PDLI resulted in a decreased TTF for all species and cultivars of angelonia and nemesia; however, the extent of the decrease was variable. For example, as PDLI increased from 2 to 17 mol·m -2·d-1, TTF decreased by 24 and 20 d for angelonia 'Carita Cascade' and 'Sundancer White' and 5 and 8 d for angelonia 'AngelMist' and 'Arch Angel White', respectively. Results from this research can be used to predict and manage growth and flowering under varying PDLIs and FDLIs for angelonia, nemesia, osteospermum, and verbena.

Degree

M.S.

Advisors

Lopez, Purdue University.

Subject Area

Horticulture|Sustainability

COinS