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Why is Temperature important?
Maintaining an optimal temperature within the greenhouse is crucial for fostering robust growth in strawberry plants and enhancing overall crop quality. A conducive temperature environment not only accelerates the growth rate of the strawberries but also positively influences key attributes such as flesh firmness, skin resistance, soluble sugar content (SSC), skin colour, and organic acids (Atkinosa et al., 2005). However, finding the optimum temperature for strawberry greenhouse production is crucial and exceedingly complicated as it depends on growth stage, cultivar, and specific greenhouse design.
Temperature Variation
Larger temperature variations between day and night contribute to an increase in total soluble solids within the harvested fruit which is in contrast to light or relative humidity (Khammayom et al., 2022). They concluded that reduction in soluble sugar content towards the end of the season can be attributed to rising temperatures. This suggests that the temperature variance between day and night plays a pivotal role in influencing strawberry production. The flower initiation in strawberry plants, generally amplifies as temperatures decrease, however, it varies among different cultivars as for some it is contingent upon a certain number of chilling hours. Low temperature below 7 °C during pollen and embryo development (7 weeks before harvest) create misshapen fruits (Ariza et al., 2012). Low temperatures reduced pollen viability, and flowers pollinated with low quality pollen led to a higher amount of misshapen fruits (Ariza et al., 2011). On the other hand, elevated temperatures can detrimentally impact the plant's photosynthetic rate, leading to a substantial decrease of up to 44% of the assimilation rate which subsequently resulted in lowering leaf area index (LAI), shoot, root, and leaf biomass . This reduction not only diminishes overall crop yield but also contributes to a decline in fruit sugar levels. Consequently, the decrease in sweetness at the fruit level is a direct consequence of the compromised photosynthetic process induced by higher temperatures (Kadir et al., 2006). High temperatures are known to reduce fruit size and fruit weight in strawberry, primarily attributed to a decline in plant fertility. However, the response to high temperature is highly cultivar dependent (Ledesma et al., 2008). Elevated temperatures at the fruit surface can accelerate the ripening process. A rapid rate of ripening may be considered a contributing factor that shortens the overall duration of the crop cycle (Palencia et al., 2013). However, this accelerated ripening due to high temperature can lead to lower taste quality, as the fruits may not develop the optimal sweetness associated with a slower and more controlled ripening process.
Elevated temperatures (24–32 °C) have been identified as detrimental to reduce strawberry flower formation and fruit quality (Heide, 1977, Klamkowski and Treder, 2008). Studies by Wang and Camp (2000) indicate a reduction in fruit size, while Kumakura and Shishido (1994) observed a decrease in fruit weight under high temperatures. Additionally, Hellman and Travis (1988) found that overall plant growth is negatively impacted at temperatures above 30 °C. Mori's research in 1998, further supports these findings, revealing that the number of achenes per fruit significantly decreased when exposed to a day/night temperature of 32/27 °C compared to milder conditions at 24/19 °C and 20/15 °C.
Optimal Temperature
Based on some studies the optimal temperature for strawberry plant growth is 15–26°C (Hancock, 1999, Strik, 1985 ). During flowering stage, it’s best to maintain a temperature range of 16-20°C. However, once the plants bear fruit, a range of 15-16°C is ideal for maturation (DryGair). However this temperature varies among different cultivars. Strawberry cultivars exhibit two primary categories based on their flowering patterns: seasonal flowering, commonly known as June-bearing, and perpetual flowering, also referred to as everbearing (Heide et al., 2013). In the case of June-bearing strawberries, flowering is triggered by the combination of short-day conditions and low temperatures in autumn. Following this initiation, the plant enters a dormant phase throughout the winter, culminating in a singular harvest season during the summer (Yamasaki, 2013). On the other hand, everbearing strawberries possess the flexibility to initiate flowering under various photoperiods and within a moderate temperature range. This adaptability results in an extended harvest season, spanning from spring through to autumn (Hossain et al., 2019).
Therefore, ensuring precise temperature adjustments tailored to different growth stages and specific cultivars is crucial in a strawberry greenhouse, as it directly influences the overall health, flowering, and fruiting potential of the plants. Insufficient monitoring of greenhouse temperatures is a challenge for growers to identify fluctuations or deviations from the optimal range. This lack of monitoring can lead to prolonged exposure to unfavourable conditions, negatively impacting plant health and productivity. Striking the right balance and making informed adjustments is critical for maintaining a stable and conducive environment.
Why Sensors are Important
Sensor technology provides a proactive approach to greenhouse temperature management by continuously monitoring temperature conditions and offering real-time data for growers to make prompt and precise adjustments. Through the utilisation of sensor technology, growers can establish a responsive and adaptive environment conducive to optimal plant growth. The integration of sensors into greenhouse operations brings forth numerous benefits, including timely decision-making through real-time data, prevention of prolonged exposure to unfavourable conditions, and enhanced precision through automated adjustments based on sensor readings. Sensor integration optimises the cultivation environment, promotes healthier plants and improves the efficiency of greenhouse management.
Conclusion
Effective temperature control is paramount for successful strawberry greenhouse cultivation. The comprehensive understanding of temperature ranges, and variations among cultivars, underscores the importance of this aspect. Embracing sensor technology emerges as a game-changer, providing growers with the tools to prevent and address temperature-related challenges proactively.
