Modeling the Effects of Temperature and Photosynthetic Daily Light Integral on Growth and Flowering of Salvia splendens and Tagetes patula

Abstract

Photosynthetic daily light integral (DLI) and temperature are two environmental factors that profoundly influence plant growth and development. Two common ornamental annual crops, salvia (Salvia splendens F. Sello ex Roem & Schult.) and marigold (Tagetes patula L.), were grown in glass greenhouses under a mean DLI of 5 to 25 mol·m−2·d−1 at temperatures from 14 to 27 °C. Growth (e.g., plant dry weight at flowering) and flowering characteristics (e.g., time to flowering and flower number) were modeled in response to the mean daily temperature and DLI by using multiple regression analysis. The rate of progress to flowering of salvia and marigold was primarily influenced by the mean air temperature. For example, time from seedling transplant to flowering of salvia decreased from 42 days to 24 days as temperature increased from 15 to 25 °C, with a mean DLI of 10 mol·m−2·d−1. Flower number and plant dry weight on the date of first flowering generally decreased with increasing temperature and decreasing DLI in both species. For example, marigold plants grown at 15 °C and a mean DLI of 25 mol·m−2·d−1 were 2.45 times greater in dry weight, had 2.12 more flowers, and had 49% larger flowers at flowering compared with plants grown at 25 °C and a mean DLI of 5 mol·m−2·d−1. The models can be used to predict the impact of changing light and temperature conditions on plant quality and flowering of these two crops.