Institute for Sustainable Agro-ecosystem Services, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Nishitokyo, Tokyo, Japan.
Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Japan.
Ann Bot. 2023 Nov 23;132(3):455-470. doi: 10.1093/aob/mcad127.
Air and root zone temperatures are important environmental factors affecting plant growth and yield. Numerous studies have demonstrated that air temperature strongly affects plant growth and development. Despite the extensive literature on air temperature, comprehensive studies on the effects of root zone temperature (RZT) on plant growth, elemental composition, and pigments are limited. In this study, we carefully observed the effects of RZT in red leaf lettuce to understand its effect on lettuce growth and pigment content.
Lettuce (Lactuca sativa, red leaf cultivar 'Red Fire') was grown hydroponically in a plant factory with artificial light under three RZT treatments (15, 25, or 35 °C) for 13 days. We investigated the comprehensive effects of RZT on the production of red leaf lettuce by metabolome and ionome analyses.
The 25 °C RZT treatment achieved maximum shoot and root dry weight. The 35 °C RZT decreased plant growth but significantly increased pigment contents (e.g. anthocyanins, carotenoids). In addition, a RZT heating treatment during plant cultivation that changed from 25 to 35 °C RZT for 8 days before harvest significantly increased shoot dry weight compared with the 35 °C RZT and significantly increased pigments compared with the 25 °C RZT. The 15 °C RZT resulted in significantly less pigment content relative to the 35 °C RZT. The 15 °C RZT also resulted in shoot and root dry weights greater than the 35 °C RZT but less than the 25 °C RZT.
This study demonstrated that plant growth and pigments can be enhanced by adjusting RZT during different stages of plant growth to attain enhanced pigment contents while minimizing yield loss. This suggests that controlling RZT could be a viable method to improve lettuce quality via enhancement of pigment content quality while maintaining acceptable yields.
空气和根区温度是影响植物生长和产量的重要环境因素。许多研究表明，空气温度强烈影响植物的生长和发育。尽管关于空气温度的文献很多，但关于根区温度（RZT）对植物生长、元素组成和色素的综合影响的研究有限。在这项研究中，我们仔细观察了 RZT 对红叶生菜的影响，以了解其对生菜生长和色素含量的影响。
生菜（Lactuca sativa，红叶品种“Red Fire”）在人工光照的植物工厂中进行水培，在 15、25 或 35°C 的三种 RZT 处理下生长 13 天。我们通过代谢组和离子组分析研究了 RZT 对红叶生菜生产的综合影响。
25°C 的 RZT 处理使地上部和地下部干重达到最大值。35°C 的 RZT 降低了植物生长，但显著增加了色素含量（如花青素、类胡萝卜素）。此外，在植物栽培过程中进行的 RZT 加热处理，即在收获前 8 天从 25°C 改变到 35°C 的 RZT，与 35°C 的 RZT 相比，显著增加了地上部干重，与 25°C 的 RZT 相比，显著增加了色素含量。15°C 的 RZT 与 35°C 的 RZT 相比，色素含量显著降低。15°C 的 RZT 也使地上部和地下部干重大于 35°C 的 RZT，但小于 25°C 的 RZT。
本研究表明，通过在植物生长的不同阶段调整 RZT，可以增强植物生长和色素，从而在最小化产量损失的情况下提高色素含量。这表明控制 RZT 可能是一种通过增强色素含量来提高生菜品质的可行方法，同时保持可接受的产量。
