Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organization (ELGO-Dimitra), Thermi, 57001 Thessaloniki, Greece.
Institute of Mediterranean Forest Ecosystems, Hellenic Agricultural Organization (ELGO-Dimitra), Terma Alkmanos, Ilisia, 11528 Athens, Greece.
Genes (Basel). 2022 Feb 17;13(2):364. doi: 10.3390/genes13020364.
Greenhouse production of baby leaf vegetables grown in hydroponic floating trays has become extremely popular in recent years. Rocket ( Mill.) can grow in temperatures varying between 10 and 20 °C; nevertheless, a root-zone temperature (RZT) range of 18-23 °C is considered optimal for high productivity, photosynthesis, and production of metabolites. Maintaining such temperatures in winter raises production costs and prevents sustainability. In this study, we tested the impact of lower RZT on plants' status and recorded their responses while providing energy for heating using photovoltaic solar panels. We used three hydroponic tanks for cultivation; a non-heated (control) tank (12 °C) and two heated tanks; a solar panel-powered one (16 °C) and a public grid-powered one (22 °C). Methylation-sensitive amplified polymorphisms (MSAP) analysis of global methylation profiles and chlorophyll fluorescence analysis were employed to assess methylation and physiology levels of rocket leaves. We found that there is demethylation at 16 °C RZT in comparison to 22 °C RZT. Reduction of temperature at 12 °C did not reduce methylation levels further but rather increased them. Furthermore, at 16 °C, the effective quantum yield of photosystem II (PSII) photochemistry (ΦPSII) was significantly higher, with a higher PSII electron transport rate (ETR) and a significantly decreased non-regulated energy loss (ΦΝO), suggesting a better light energy use by rocket plants with higher photosynthetic performance. ΦPSII was significantly negatively correlated with DNA methylation levels. Our results show that at 16 °C RZT, where plants grow efficiently without being affected by the cold, DNA methylation and photosynthesis apparatus systems are altered. These findings corroborate previous results where hydroponic production of rocket at RZT of 16 °C is accompanied by sufficient yield showing that rocket can effectively grow in suboptimal yet sustainable root-zone temperatures.
近年来，水培漂浮盘中种植的婴儿叶菜的温室生产变得非常流行。火箭菜（Mill.）可以在 10 到 20°C 的温度范围内生长；然而，18-23°C 的根区温度（RZT）范围被认为是高产、光合作用和代谢产物生产的最佳温度。在冬季保持这样的温度会增加生产成本并影响可持续性。在这项研究中，我们测试了较低的 RZT 对植物状况的影响，并记录了它们的反应，同时使用光伏太阳能电池板为加热提供能源。我们使用了三个水培罐进行种植；一个未加热（对照）罐（12°C）和两个加热罐；一个由太阳能电池板供电的（16°C）和一个由公共电网供电的（22°C）。使用甲基化敏感扩增多态性（MSAP）分析技术对全球甲基化谱和叶绿素荧光分析进行了分析，以评估火箭叶的甲基化和生理水平。我们发现，与 22°C RZT 相比，16°C RZT 时存在去甲基化。在 12°C 时降低温度不会进一步降低甲基化水平，反而会增加甲基化水平。此外，在 16°C 时，光系统 II（PSII）光化学的有效量子产量（ΦPSII）显著更高，PSII 电子传递率（ETR）更高，非调节能量损失（ΦΝO）显著降低，这表明火箭植物更好地利用了光能，具有更高的光合作用性能。ΦPSII 与 DNA 甲基化水平呈显著负相关。我们的结果表明，在 16°C 的 RZT 下，植物在不受寒冷影响的情况下高效生长，DNA 甲基化和光合作用装置系统发生改变。这些发现与之前的结果一致，即在 16°C 的 RZT 下进行水培生产火箭菜时，产量充足，表明火箭菜可以在亚最佳但可持续的根区温度下有效生长。
