# Optimizing Daily Light Integral in Seedling Stage Accelerates Heading and Flowering in Wheat Under LED Lighting

## TL;DR

This study finds that optimizing light exposure during the seedling stage of wheat can significantly speed up flowering and heading under controlled LED lighting.

## Contribution

The study identifies an optimal daily light integral (DLI) for wheat seedlings that accelerates growth and improves plant quality in speed-breeding systems.

## Key findings

- An optimal DLI of 39.6 mol m−2 d−1 maximized seedling index, root-to-shoot ratio, and photosystem performance.
- Using the optimal DLI led to flowering and heading 5.9 and 7.5 days earlier than with the lowest DLI.
- Higher DLIs beyond 39.6 mol m−2 d−1 did not improve growth parameters or biomass.

## Abstract

Conventional wheat breeding in the field is limited to two generations per year and is susceptible to environmental fluctuations. Speed-breeding in a plant factory offers a solution; however, recommendations for lighting strategies remain limited. To identify the optimal daily light integral (DLI) for the seedling stage, we tested three light intensities (300, 500, and 700 μmol m−2 s−1) and four photoperiods (10, 14, 18, and 22 h d−1), resulting in DLIs ranging from 10.8 to 55.4 mol m−2 d−1. Our results indicated that an optimal DLI of 39.6 mol m−2 d−1 was associated with the highest seedling index (0.26) and root-to-shoot ratio (0.42), as well as enhanced photosystem performance. Beyond this DLI, these parameters and shoot biomass plateaued as the DLI increased. Moreover, treating seedlings with this optimal DLI of 39.6 mol m−2 d−1 (using 500 μmol m−2 s−1 light intensity and a 22 h d−1 photoperiod) resulted in heading and flowering 5.9 and 7.5 days earlier after transplanting, respectively, than those under the lowest DLI (10.8 mol·m−2·d−1). This study established a lighting strategy to produce high-quality seedlings and accelerate heading and flowering, thereby offering a valuable physiological framework for advancing speed-breeding systems in wheat.