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- Author or Editor: Yasunaga Iwasaki x
Uniform flower development is crucial for the uniform production of mature fruit, and it is essential in the management and production of commercial strawberry (Fragaria ×ananassa) in greenhouses. Environmental factors such as temperature, light intensity, and photoperiod have been extensively evaluated to determine their roles in strawberry flower induction and growth; however, data on the role that lighting conditions play in the uniformity of flower development are still lacking. The aim of this study was to clarify the influence of light intensity on the uniformity of strawberry flower development in forcing culture. Two experiments were conducted to evaluate plants’ response to both shading and light-emitting diode (LED) treatments. Plant growth parameters (i.e., leaf area, dry matter, and number of leaves between inflorescences) and flower development data [i.e., time from flower beginning to full bloom (FB), time from transplanting to flowering (TB), and bud number (BN)] were recorded. As expected, flower development was enhanced when exposed to LED light and was delayed when shaded. Within each cultivar, a strong relationship between lighting environment and uniformity of flower development was also detected. In both experiments, TB and BN showed less variation when exposed to high light intensity compared with low intensity. This trend was true for other parameters as well, including dry matter, leaf area, and number of leaves between inflorescences. However, there were no significant differences in FB between the shading and LED treatments. The results show that strawberry growth and flower development were highly variable in a low light environment. In addition to light being an important factor in inflorescence initiation and high yield production, the results of this study also show that the amount of light supplied is an important factor in maintaining uniform flowering in forcing culture.
Root-zone temperature (RZT) is closely related to nutrient transportation and biomass production. However, its influence on biomass production and dry matter distribution remains unknown, especially in year-long production greenhouses. We explore the potential of RZT as an environmental control method to promote spinach field production by quantifying the effects of RZT to increase spinach production. Three RZT treatments using a nutrient film technique (NFT) system quantified and evaluated the effects of spring, summer, and winter spinach cultivation. We investigated the growth characteristics, total aboveground dry matter, and fraction of dry matter distribution to the leaf and root (which corresponded with yield). The RZT effects on total aboveground dry matter varied with the average air temperature inside the greenhouse. The total aboveground dry matter correlated positively with RZT in optimal air temperature conditions (15–20 °C). The dry matter-to-leaves ratio of the spinach did not correlate significantly with RZT in suboptimal (5 °C < air temperature < 15 °C) or supraoptimal (20 °C < air temperature) conditions. Therefore, RZT can promote biomass accumulation. We suggest RZT provides a feasible method for controlling the dry matter distribution fraction. Further research into the functional role of RZT will support hydroponic growers in improving crop yield.
Floral initiation is an important transition point from vegetative growth to reproductive growth in tomatoes and is known to be affected by light intensity, temperature, and nutrients. However, the regulation between flower formation and environmental factors, including nutrient conditions, due to source–sink dynamics (supply and demand of photoassimilates) is seldom documented. To evaluate the effects of light intensity and nutrition conditions on prefloral formation and development, dynamic floral characteristics during development were fitted with sigmoidal logistic curves under four light treatments with shading nets in two nutrient conditions. Source activity and sink strength were altered, which caused differences in the floral positions, length of floral shoots, floral initiation dates, and leaf numbers under the different treatments. Accumulated light acts upstream of nutrition supply during the formation of buds and leads to the accumulation of carbohydrates in source organs. Leaf area reached ≈500 cm2, and dry matter weights reached ≈3 g in each treatment until the flowering day, revealing that some level of photoassimilates are necessary for floral initiation. Both days to flowering and bud number were highly correlated with daily light integral (DLI) from 6 to 12 days before anthesis, which means this period is important for anthesis in tomato. Our results highlight regulation of the transition from vegetative growth to reproductive growth by tomato seedlings due to environmental factors and nutrients. A better understanding of communication between source organs and sink organs during floral initiation response to different environments is expected to provide management strategies for greenhouse tomato production.