Early production and high energy efficiency are important in greenhouse vegetable production in cold regions. A dynamic temperature integration strategy with low pre-night temperature (PNT) has been developed to reduce energy consumption and to improve early fruit yield and energy use efficiency. However, the application of this temperature control strategy is feasible only if there is no crop yield and quality loss. To determine the low PNT tolerance threshold and explore the mechanism of this temperature control strategy on plant growth and development, the effects of four PNT temperature integration treatments (PNT9, PNT11, PNT13, and PNT15, with an actual PNT of 9.4, 11.3, 13.3, and 15.1 °C, respectively) on greenhouse tomatoes (Solanum lycopersicum) were investigated. The PNT was applied at the beginning of the night for 3 h, whereas temperatures in other periods during a day (24 h) were adjusted accordingly to ensure the same 24-h average temperature (19.4 °C) for all PNT treatments. Four cultivars (Bigdena, Clarance, Quest, and Conchita), representing all three types (beefsteak, cluster, and cherry) of greenhouse tomatoes, were used in the study. The optimum PNT for fruit yield was 13.8 and 14.9 °C for ‘Bigdena’ and ‘Conchita’, respectively. Low PNT down to 11 °C did not compromise fruit yield and plant development in ‘Clarance’, and thus a PNT lower than 13 °C can be used for ‘Clarance’ if it does not have a negative effect on fruit quality. In ‘Bigdena’ and ‘Conchita’, the above-ground biomass increased with increasing PNT at the low range of PNT, peaked at ≈13 °C PNT (13.7 and 13 °C for ‘Bigdena’ and ‘Conchita’, respectively), then declined at high PNT. Leaf photosynthesis rates were increased by the highest PNT (PNT15), whereas respiration rates were reduced by the lowest PNT (PNT9). Therefore, PNT at ≈13 °C might have allowed for the proper balance between the high photosynthesis for photoassimilate generation and the low respiration for photoassimilate conservation and thus accumulated the highest photoassimilate and the highest fruit yield in ‘Bigdena’. Flower development rate in ‘Conchita’ decreased linearly with low PNT, which might have limited the response of its fruit yield to low PNT and raised the optimum PNT for fruit yield to 14.9 °C. Temperature integration with proper low PNT can be an effective climate control strategy for increasing early fruit yield and energy use efficiency in greenhouse tomato production.
Lu Zhang, Xiuming Hao, Yonggeng Li and Gaoming Jiang
Xuhong Zhou, Xijun Mo, Yalian Jiang, Hao Zhang, Rongpei Yu, Lihua Wang, Jihua Wang and Suping Qu
The omission of second division gene (OSD1) gene plays a fundamental role in meiosis and is associated with 2n gamete formation in Arabidopsis thaliana. The objective of this work was to unravel the mechanisms leading to 2n pollen production, and isolate and analyze the expression patterns of OSD-like (OSDL) genes in carnation (Dianthus caryophyllus). We found an absence of the second meiotic division caused the formation of 2n pollen. Three homoeologous genes were cloned and labeled as OSDLa, OSDLb, and OSDLc in a diploid carnation. The cDNAs were 1180 bp for OSDLa, 1288 bp for OSDLb, and 971 bp for OSDLc. A strong similarity was found between the amino sequences of OSDLb and OSDLc. An evident feature of OSDLs proteins is the presence of D-box and MR-tail domains; however, the GxEN/KEN-box domain, which is distinct among the other plant proteins was absent. Quantitative real time polymerase chain reaction (qRT-PCR) analysis showed that OSDL genes maintain continuous expression in buds and other tissues. OSDLa has the highest expression in buds of 1.1–1.2 cm long (stage 2), and OSDLb has a high level of expression in buds of 0.9–1.0 cm long (stage 1) and stage 2 buds and ovary tissues in three carnation cultivars. The expression level of OSDLc was highest in ovaries. These expression patterns strongly suggest that OSDLs in carnation involve male meiosis and ovary development. These findings can have potential applications in fundamental polyploidization research and plant breeding programs in carnation.