Root-zone Temperature Research Articles

Highest Occurring Vascular Plants from Ladakh Provide Wood Anatomical Evidence for a Thermal Limitation of Cell Wall Lignification.

As an evolutionary achievement of almost all terrestrial plants, lignin biosynthesis is essential for various mechanical and physiological processes. Possible effects of plant cell wall lignification on large-scale vegetation distribution are, however, not yet fully understood. Here, we present double-stained, wood anatomical stem measurements of 207 perennial herbs (Potentilla pamirica Wolf), which were collected between 5550 and 5850 m asl on the north-western Tibetan Plateau in Ladakh, India. We also measured changes in situ root zone and surface air temperatures along the sampling gradient and applied piecewise structural equation models to assess direct and indirect relationships between the age and size of plants, the degree of cell wall lignification in their stems, and the elevation at which they were growing. Based on the world's highest-occurring vascular plants, the Pamir Cinquefoils, we demonstrate that the amount of lignin in the secondary cell walls decreases significantly with increasing elevation (r = -0.73; p < 0.01). Since elevation is a proxy for temperature, our findings suggest a thermal constrain on lignin biosynthesis at the cold range limit of woody plant growth.

Responses of 'Flordaguard' and 'MP-29' Prunus spp. rootstocks to hypoxia and high root zone temperature.

Selecting the right rootstock is crucial for successful fruit production and managing both biotic and abiotic stresses in commercial fruit orchards. To enhance the resilience of peach orchards, this study evaluated the physiological and biochemical responses of Prunus spp. rootstocks , 'Flordaguard' and 'MP-29,' under normoxia (sufficient oxygen content) or short-term hypoxia (low-oxygen content) and ambient or high temperature (40°C) in the root zone. Physiological responses measured were net photosynthesis, stomatal conductance, transpiration, intercellular CO2 concentration, water use efficiency, the leaf chlorophyll index, and the maximum potential quantum efficiency of photosystem II. The leaf concentrations of nitrogen, phosphorus, potassium, magnesium, calcium, sulfur, boron, zinc, manganese, iron, and copper were also analyzed. Reactive oxygen species (ROS) and antioxidants analyzed were superoxide dismutase (SOD) activity, peroxidase (POD) activity, catalase (CAT) activity, ascorbate peroxidase (APX) activity, glutathione peroxidase (GPX) activity, proline content, glycine betaine content (GB), lipid peroxidation (LPO), superoxide (O2 -) concentration, and hydrogen peroxide (H2O2) concentration. When subjected to root zone hypoxia or high temperature individually, 'MP-29' performed better physiologically than 'Flordaguard'. However, when root zone hypoxia and high temperature were combined, 'MP-29' performed better biochemically with enhanced antioxidant activity, osmolyte content, and nutrient absorption. Nutrient analysis of leaves revealed that 'MP-29' had higher N, P, K, Ca, and B concentrations than 'Flordaguard'. Consequently, 'MP-29' demonstrated greater tolerance to short-term exposure to the combined effects of high root zone temperature and hypoxia. This research contributes to identifying a suitable rootstock within the Prunus genus able to withstand root zone conditions that often result from severe weather events commonly experienced in Florida and other parts of the world.

Effects of root zone temperature and light intensity on plant growth, flowering and fruit quality of plant factory ‘festival’ strawberry (Fragaria × ananassa Duch.)

Effects of root zone temperature and light intensity on plant growth, flowering and fruit quality of plant factory ‘festival’ strawberry (Fragaria × ananassa Duch.)

Development of a root-zone temperature control system using air-source heat pump and its impact on the growth and yield of paprika.

By developing and implementing a local temperature control system, such as a root zone, with a high energy efficiency heat source, we can ensure both yield and energy efficiency against extreme temperatures. This system, designed with practicality in mind, has a remarkably positive impact on paprika plants' growth and yield in greenhouse cultivation. In the summer season, paprika plants were grown with no cooling, nutrient solution cooling (NSC) and the combination of NSC and substrate surround cooling (SSC) (NSC + SSC). In the case of SSC, cooled water circulated through the pipe surrounding the substrate to lower the substrate temperature. The cooling system maintains the nutrient solution temperature at 18 °C and the circulating water temperature at the system in the winter season; the paprika plants were grown with no heating (NH), nutrient solution heating (NSH) and the combination of NSH and substrate surround heating (SSH) (NSH + SSH). The heating system maintains the nutrient solution temperature at 25 °C and the circulating water temperature at 30 °C. In the summer, the root fresh and dry weights, stem fresh and dry weights, stem length and node number were increased in the NSC + SSC. In the winter season, the stem fresh and dry weights, leaf area and leaf fresh and dry weights were increased in the NSH + SSH. In both seasons, root-zone temperature control increased the fruit quality and yield. The result indicates that this easy-to-install root-zone temperature control system can be applied to the commercial greenhouse to secure paprika growth and yield in year-round cultivation.

Comparison of transcriptome and metabolome analysis revealed cold-resistant metabolic pathways in cucumber roots under low-temperature stress in root zone.

Low ground temperature is a major factor limiting overwintering in cucumber cultivation facilities in northern alpine regions. Lower temperatures in the root zone directly affect the physiological function of the root system, which in turn affects the normal physiological activity of plants. However, the importance of the ground temperature in facilities has not attracted sufficient attention. Therefore, this study tested the cucumber variety Jinyou 35 under three root zone temperatures (room temperature, 20-22°C; suboptimal temperature, 13- 15°C; and low temperature, 8-10°C) to investigated possible cold resistance mechanisms in the root of cucumber seedlings through hormone, metabolomics, and transcriptomics analyses. The results showed that cucumber roots were subjected to chilling stress at different temperatures. Hormone analysis indicated that auxin content was highest in the roots. Jasmonic acid and strigolactone participated in the low-temperature stress response. Auxin and jasmonate are key hormones that regulate the response of cucumber roots to low temperatures. Phenolic acid was the most abundant metabolite in cucumber roots under chilling stress. Additionally, triterpenes may play an important role in chilling resistance. Differentially expressed genes and metabolites were significantly enriched in benzoxazinoid biosynthesis in the room temperature vs. suboptimal temperature groups and the room temperature vs. low temperature groups. Most differentially expressed transcription factor genes in AP2/ERF were strongly induced in cucumber roots by both suboptimal and low-temperature stress conditions. These results provide guidance for the cultivation of cucumber in facilities.

Effects of air and root zone temperature on the distribution of 13C photosynthates in asparagus plants

Effects of air and root zone temperature on the distribution of ¹³C photosynthates in asparagus plants

A Transcriptomic Analysis of Bottle Gourd-Type Rootstock Roots Identifies Novel Transcription Factors Responsive to Low Root Zone Temperature Stress.

The bottle gourd [Lagenaria siceraria (Molina) Standl.] is often utilized as a rootstock for watermelon grafting. This practice effectively mitigates the challenges associated with continuous cropping obstacles in watermelon cultivation. The lower ground temperature has a direct impact on the rootstocks' root development and nutrient absorption, ultimately leading to slower growth and even the onset of yellowing. However, the mechanisms underlying the bottle gourd's regulation of root growth in response to low root zone temperature (LRT) remain elusive. Understanding the dynamic response of bottle gourd roots to LRT stress is crucial for advancing research regarding its tolerance to low temperatures. In this study, we compared the physiological traits of bottle gourd roots under control and LRT treatments; root sample transcriptomic profiles were monitored after 0 h, 48 h and 72 h of LRT treatment. LRT stress increased the malondialdehyde (MDA) content, relative electrolyte permeability and reactive oxygen species (ROS) levels, especially H2O2 and O2-. Concurrently, LRT treatment enhanced the activities of antioxidant enzymes like superoxide dismutase (SOD) and peroxidase (POD). RNA-Seq analysis revealed the presence of 2507 and 1326 differentially expressed genes (DEGs) after 48 h and 72 h of LRT treatment, respectively. Notably, 174 and 271 transcription factors (TFs) were identified as DEGs compared to the 0 h control. We utilized quantitative real-time polymerase chain reaction (qRT-PCR) to confirm the expression patterns of DEGs belonging to the WRKY, NAC, bHLH, AP2/ERF and MYB families. Collectively, our study provides a robust foundation for the functional characterization of LRT-responsive TFs in bottle gourd roots. Furthermore, these insights may contribute to the enhancement in cold tolerance in bottle gourd-type rootstocks, thereby advancing molecular breeding efforts.

Evaluating temperature variation of nutrient solution in Nutrient Film Technique (NFT) cooling system for temperate vegetable

The production of leafy green vegetables in hydroponic systems within greenhouses has gained global prominence in the fresh vegetable production industry. Hydroponic systems, particularly Nutrient Film Technique (NFT), are highly effective due to their soilless nature and efficient nutrient and water circulation. However, maintaining ideal greenhouse temperatures can be challenging. One strategy to reduce energy costs is to heat or cool the nutrient solution instead of the entire greenhouse environment. By regulating the root zone temperature through nutrient solution management, growers can provide more favourable conditions for temperate leafy greens. These conditions are critical because temperatures above 23°C can inhibit plant growth, while temperatures exceeding 35°C can significantly reduce plant metabolism efficiency. This study investigates how lettuce responds to nutrient solution cooling. Importantly, this research focuses on Malaysia, an equatorial country with a consistently warm and humid climate. In such environments, controlling nutrient solution or air temperature to match the crops' optimal growth requirements is crucial. The study employed Butterhead and Romaine lettuce varieties in a hydroponic NFT system. The EC (Environmental Cooling) treatment involved cooling the nutrient solution, while the RZC (Root Zone Cooling) treatment utilized environmental cooling. The results demonstrated that maintaining a consistent nutrient solution temperature within the range of 14°C to 18°C (as observed in the EC treatment) led to superior plant growth and quality, particularly in the early growth stages. In contrast, the RZC treatment showed temperature fluctuations, causing plant stress and inhibiting growth.

Raising root zone temperature improves plant productivity and metabolites in hydroponic lettuce production.

While it is commonly understood that air temperature can greatly affect the process of photosynthesis and the growth of higher plants, the impact of root zone temperature (RZT) on plant growth, metabolism, essential elements, as well as key metabolites like chlorophyll and carotenoids, remains an area that necessitates extensive research. Therefore, this study aimed to investigate the impact of raising the RZT on the growth, metabolites, elements, and proteins of red leaf lettuce. Lettuce was hydroponically grown in a plant factory with artificial light at four different air temperatures (17, 22, 27, and 30°C) and two treatments with different RZTs. The RZT was raised 3°C above the air temperature in one group, while it was not in the other group. Increasing the RZT 3°C above the air temperature improved plant growth and metabolites, including carotenoids, ascorbic acids, and chlorophyll, in all four air temperature treatments. Moreover, raising the RZT increased Mg, K, Fe, Cu, Se, Rb, amino acids, and total soluble proteins in the leaf tissue at all four air temperatures. These results showed that raising the RZT by 3°C improved plant productivity and the metabolites of the hydroponic lettuce by enhancing nutrient uptake and activating the metabolism in the roots at all four air temperatures. Overall, this research demonstrates that plant growth and metabolites can be improved simultaneously with an increased RZT relative to air temperature. This study serves as a foundation for future research on optimizing RZT in relation to air temperature. Further recommended studies include investigating the differential effects of multiple RZT variations relative to air temperature for increased optimization, examining the effects of RZT during nighttime versus daytime, and exploring the impact of stem heating. This research has the potential to make a valuable contribution to the ongoing growth and progress of the plant factory industry and fundamental advancements in root zone physiology. Overall, this research demonstrates that plant growth and metabolites can be improved simultaneously with an increased RZT relative to air temperature. This study serves as a foundation for future research on optimizing RZT in relation to air temperature. Further recommended studies include investigating the differential effects of multiple RZT variations relative to air temperature for increased optimization, examining the effects of RZT during nighttime versus daytime, and exploring the impact of stem heating. This research has the potential to make a valuable contribution to the ongoing growth and progress of the plant factory industry and fundamental advancements in root zone physiology.

Effects of cold storage duration and root zone temperature on flowering of amaryllis (Hippeastrum striatum ‘Blossom Peacock’)

Effects of cold storage duration and root zone temperature on flowering of amaryllis (Hippeastrum striatum ‘Blossom Peacock’)

Enhancing Productivity and Improving Nutritional Quality of Subtropical and Temperate Leafy Vegetables in Tropical Greenhouses and Indoor Farming Systems

The total land used for land-based food farms is less than 1% in Singapore. As a result, more than 90% of Singapore’s food needs are imported. To strengthen food security, Singapore has set a target to develop the capability and capacity of the agri-food industry to locally produce 30% of its nutritional needs by 2030. To achieve this goal, technology is the key to helping farms to “grow more with less”. This review first discusses how aeroponic systems have been adapted for growing all kinds of leafy vegetables in the tropics through the manipulation of root-zone temperature and heat priming to save power energy. Growing vegetable crops indoors and in greenhouses not only allows the growers to achieve high productivity but also enables them to enhance nutritional values. The second part of this paper emphasizes how to achieve substantial yield through deficit irrigation with higher nutritional quality in a cost-effective manner. Growing crops vertically has become increasingly popular, as it increases land use. We establish a commercially viable LED-integrated aeroponic system to grow vegetables vertically. The last part of the paper discusses the impacts of LED spectral quality, quantity, and duration on vegetable production.

The sensitivity of root water uptake to cold root temperature follows species-specific upper elevational distribution limits of temperate tree species.

Physiological water stress induced by low root temperatures might contribute to species-specific climatic limits of tree distribution. We investigated the low temperature sensitivity of root water uptake and transport in seedlings of 16 European tree species which reach their natural upper elevation distribution limits at different distances to the alpine treeline. We used 2H-H2O pulse-labelling to quantify the water uptake and transport velocity from roots to leaves in seedlings exposed to constant 15°C, 7°C or 2°C root temperature, but identical aboveground temperatures between 20°C and 25°C. In all species, low root temperatures reduced the water transport rate, accompanied by reduced stem water potentials and stomatal conductance. At 7°C root temperature, the relative water uptake rates among species correlated positively with the species-specific upper elevation limits, indicating an increasingly higher sensitivity to lower root zone temperatures, the lower a species'natural elevational distribution limit. Conversely, 2°C root temperature severely inhibited water uptake in all species, irrespective of the species'thermal elevational limits. We conclude that low temperature-induced hydraulic constraints contribute to the cold distribution limits of temperate tree species and are a potential physiological cause behind the low temperature limits of plant growth in general.

Effects of Long-Term High Temperatures in the Root Zone on the Physiological Characteristics of Grapevine Leaves and Roots: Implications for Viticulture Practices

Ridging cultivation and root restriction cultivation are beneficial due to their improvement of the soil permeability in the root zone of grapevine, and they are widely used in southern China, Japan, and other countries. However, with the intensification of global warming, when using ridging or root restriction cultivation, the soil temperature in the root zone can often reach 30 °C or even more than 35 °C during the summer, which is not conducive to the growth of grapevines. The aim of this study was to explore the effects of high root zone temperatures on the photosynthetic fluorescence characteristics of grapevine leaves, root respiration, and degree of lignification of roots and shoots, as well as to provide a theoretical foundation for the management of grapevine production and cultivation. One-year-old potted ‘Kyoho’ was used as the study material. Three root temperature treatments were implemented for 15 days (9:00–16:00): 25 °C (CK), 30 °C (T1), and 35 °C (T2). The results showed that the malondialdehyde and H2O2 levels in leaves increased, while the chlorophyll content decreased. The oxygen-evolving complex was inactivated, and PSII donor and acceptor sides were blocked, thus reducing the photosynthetic gas exchange capacity at high root zone temperatures. The grapevine root activity and root/shoot ratio decreased. Simultaneously, the lignin content in the roots and shoots increased. In addition, there was a significant increase in the expression of key genes (PAL, C4H, 4CL, F5H, COMT, CCR, and CAD) in the root lignin synthesis pathway. Heightened root zone temperatures increased cyanide-resistant respiration in roots and heat release in the PPP pathway to alleviate stress damage. Therefore, it is recommended to use grass, mulching, and other cultivation management methods to maintain root zone temperatures below 30 °C in order to ensure the normal growth of grapevines and promote a high and stable yield.

Plant Growth, Fruit Yield, and Tomato Leaf Curl Disease of High Tunnel Organic Tomato Affected by Shade Net and Plastic Mulch Color

There is an increasing interest in producing organic tomatoes (Solanum lycopersicum) in high tunnels (HTs) in the southeast United States. HTs are unheated, passively cooled structures that allow tomato growers to harvest high-quality fruit out of season. However, excessive temperatures inside HTs may negatively impact tomato plant growth and fruit yield. Shade nets have been reported to reduce temperatures inside the HTs. Plastic mulch color has also significantly influenced plant growth and yield under high-temperature conditions. This study aimed to determine the effects of shade net color and plastic mulch color on plant growth, fruit yield, and incidence of tomato yellow leaf curl disease (TYLC) in ‘Red Snapper’ tomato grown in HTs under elevated temperatures (summer-fall) in southern Georgia, USA. Organic ‘Red Snapper’ tomato seedlings were transplanted in HTs in 2019 (Season 1) and 2020 (Season 2). The design was a split-plot randomized block where the main plots were externally mounted shade nets (black, silver, and unshaded; 30% shade factor), and the subplots were plastic mulches (black and white). Compared with black mulch, white mulch improved plant height and stem diameter but did not influence fruit yields. Shade nets reduced HT air temperature and root zone temperature (RZT) but did not affect plant height and stem diameter. The diminished photosynthetic photon flux density (PPFD) under the shade nets reduced marketable fruit yield. Thus, shade nets are not recommended once heat challenges do not limit HT tomato production in Georgia (after about mid-October). Shade nets and plastic mulch inconsistently affected TYLC incidence, severity, and area under the disease progress curve (AUDPC). Additional fruit yield reductions occurred due to TYLC because the incidence was 100% 6 weeks after transplanting. Preliminary insect data showed that shade net treatments had similar sweetpotato whitefly (Bemisia tabaci) numbers. The high TYLC incidence indicates that ‘Red Snapper’ may not be suitable for fall HT tomato production in the southeast United States. More research on shading and heat stress management in HT organic tomato production is necessary.

Control of Air and Root Zone Temperature Enhances Early Growth of Paprika in Greenhouses

Control of Air and Root Zone Temperature Enhances Early Growth of Paprika in Greenhouses

Controlling root zone temperature improves plant growth and pigments in hydroponic lettuce.

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.

Successful cultivation of Darlingtonia californica in a hot climate via root zone chilling

Maintenance of consistent cool root zone temperatures is the factor most critical for successful Darlingtonia californica cultivation. Darlingtonia plants grown semi-hydroponically with chilled water will tolerate ambient temperatures substantially warmer those grown conventionally.

Effects of the Air Temperature and Root Zone Temperature in Greenhouses on the Early Growth of Tomatoes

Effects of the Air Temperature and Root Zone Temperature in Greenhouses on the Early Growth of Tomatoes

Testing of moisture-saturating polymers and synthetic mulching materials for growing fruit and berry crops

The article studies the growth and development of red raspberry (Rubus idaelus L.), Nanjing cherry (Prunus tomentosa Thunb.), golden currants (Ribes aureum Pursh.), and sea buckthorn (Hippophaerhamnoides L.) in the variants of the experiment polymer gel + film + additional wetting by rainwater and meltwater runoff; polymer gel + film; polymer gel; control (without polymer gel and film). It was established that the use of a mulching black film could increase the moisture content of the root zone by up to 40%. When determining the water deficit, it was found that the experimental plants lost less moisture. Under the influence of hydrogels, the irrigation depth of fruit and berry crops was reduced by 50%. It was found that the black mulch film had a warming effect on the soil, which also had a positive effect on plant growth and development increasing the root zone temperature. Red raspberry bushes formed better when using hydrogels in the soil; during seasonal observations, an increased number of first-year canes was noted up to 2.5 higher than in the control. The hydrogel and mulching film had the best effect on Nanjing cherries, increasing the number of leaves on experimental plants and formed fruit shoots. Sea buckthorn under the film exceeded biometric indicators by 2 times vs the control plants. In golden currant plants, the best growth and development were observed in the variant using hydrogel and mulching film; foundation stocks developed intensively and bore fruit better with the experiment continuation, it is possible to obtain high profits from the sale of grown products. The use of hydrogels and mulch film reduces herbicide costs by reducing weeds and producing organic fruits and berries.

Evaluation of salt and root-zone temperature stresses in leafy vegetables using hydroponics as a clean production cultivation technique in northeastern Brazil

Evaluation of salt and root-zone temperature stresses in leafy vegetables using hydroponics as a clean production cultivation technique in northeastern Brazil