Effects of Root Zone Warming on Maize Seedling Growth and Photosynthetic Characteristics Under Different Phosphorus Levels

Phosphorus content and root zone temperature are two major environmental factors affecting maize growth. Both low phosphorus and root zone high temperature stress significantly affect the growth of maize, but the comprehensive effects of phosphorus deficiency and root zone warming are less studied. This study aimed to explore the effects of phosphorus deficiency and root zone warming on the root absorption capacity, total phosphorus content, and photosynthetic fluorescence parameters of maize seedlings. The results showed that maize shoots and roots had different responses to root zone warming and phosphorus deficiency. Properly increasing the root zone temperature was beneficial to the growth of maize seedlings, but when the root zone temperature was too high, it significantly affected the root and shoot development of maize seedlings. The root zone warming had a more significant impact on the root system, while phosphorus deficiency had a greater impact on the shoots. Phosphorus content and root zone warming had a strong interaction. Under the comprehensive influence of normal phosphorus supply and medium temperature in the root zone, the growth of maize seedlings was the best. Under the combined effects of low phosphorus and high temperature in the root zone, the growth was the worst. Compared with the combination of normal phosphorus and root zone medium temperature treatment, the dry mass of the low-phosphorus root zone high temperature treatment was decreased by 55.80%. Under the condition of low-phosphorus too high root zone temperature reduced root vitality, plant phosphorus content, which in turn affected plant growth and light energy utilization efficiency. In the case of sufficient phosphate fertilizer supply, appropriately increasing the soil temperature in the root zone is beneficial to increase the absorption and utilization of phosphorus by plants and promote the growth and development of maize seedlings.

Heat transfer assessment of multi-tier chilling pipes for root zone cooling system under crop protection structure in the tropics

Root zone cooling technique has become an alternative cultivation method for temperate crops production in the tropics instead of cooling the aerial environment of the greenhouse. In this experiment, the root zone cooling system was incorporated with a multi-tier crop cultivation structure. This structure consisted of five tiers arranged in an A-shape design and was placed under an open rain shelter, thus, left it to undergo fluctuating environment temperature. There were five pillow polybags inserted with cocopeat and were placed on the structure. Each pillow polybag consisted of a single pipe that was buried inside the growth media located near the root zone area. This pipe that was connected to the chilled system acted as a cooling agent in controlling the growth media temperature. The objective of the study was to evaluate the Root Zone Cooling (RZC) system performance in distributing and controlling water-dissolved nutrient temperatures to meet crop-root requirement needs. From the experiment conducted, it was found that there was no significant difference between root zone temperature at different levels and lengths on multi-tier structure. The chilling pipes was able to distribute the temperatures to meet crop-root requirement needs along the multi-tier structure.

The Potential Effect of Elevated Root Zone Temperature on the Concentration of Chlorogenic, Caffeic, and Ferulic acids and the Biological Activity of Some Pigmented Solanum tuberosum L. Cultivar Extracts

Without a doubt, potatoes play a vital food and nutrition security role in the world as more than a billion people consume this vegetable. Furthermore, the polyphenolic constituents of pigmented potato cultivars and their associated health benefits have been reported. However, the antioxidant, anticancer, and antimycobacterial activity of pigmented cultivars are scanty. Therefore, the present study explores the phenolic acids and biological activities of cv. Salad Blue (SB) and non-pigmented control (BP1) extracts. The antiproliferative activity of S. tuberosum L. against human hepatocellular carcinoma (HepG2) was investigated, as well as the ability to inhibit Mycobacterium smegmatis. Chlorogenic acid was the most prominent phenolic acid in both treatments as well as cultivars. In the current trial, 24 °C significantly increased chlorogenic acid in cv. SB and BP1. Ethanolic extracts of all the samples showed no activity at the highest test concentration of 1000 μg/mL (ciprofloxacin MIC of 0.325 μg/mL) against M. smegmatis. The antiproliferative activity of the tuber samples against HepG2 liver cells had IC50 values ranging between 267.7 ± 36.17 μg/mL and >400 μg/mL. Since the health benefits of these cultivars are highly valued, the present study provides useful information for future oncology studies, for human nutrition, as well as for how these underutilized cultivars can be fortified to improve their health benefits.

Efficacy of Root Zone Temperature Increase in Root and Shoot Development and Hormone Changes in Different Maize Genotypes

In the context of global warming, the effects of warming in the root zone of crops on maize seedling characteristics deserve research attention. Previous studies on the adaptive traits of dryland maize have mainly focused on soil moisture and nutrients, rather than analyzing potential factors for the adaptive traits of root zone warming. This study was conducted to investigate the effects of different root zone warming ranges on the agronomic traits, hormones, and microstructures of maize seedling roots and leaves. The results showed that minor increases in the root zone temperature significantly enhanced maize seedling growth. However, when the temperature in the root zone was excessive, the stem diameter, root surface area, root volume, total root length, dry matter accumulation, and root/shoot biomass of maize seedlings sharply decreased. Under high temperature stress in the root zone, the root conduit area; root stele diameter; root content of trans-zeatin (ZT), gibberellin A3 (GA3), and indoleacetic acid (IAA); leaf thickness; upper and lower epidermis thickness; and leaf content of ZT and GA3 were significantly decreased. The hormone content and microstructure changes might be an important reason for root growth maldevelopment and nutrient absorption blockage, and they also affected the leaf growth of maize seedlings. Compared with the ‘senescent’ maize type Shaandan 902 (SD902), the plant microstructure of the ‘stay-green’ maize type Shaandan 609 (SD609) was less affected by increased temperatures, and the ability of the root system to absorb and transport water was stronger, which might explain its tolerance of high temperature stress in the root zone.

Studies of Vegetative Growth, Inflorescence Development and Eco-Dormancy Formation of Abscission Layers in Streptocarpus formosus (Gesneriaceae)

Streptocarpus formosus (Hilliard & B.L. Burtt) T.J. Edwards is a flowering herbaceous perennial indigenous to South Africa and is part of the rosulate group of herbaceous acaulescent plants within the Gesneriaceae family. According to the National Assessment database for the Red List of South African Plants version 2020.1., the plant is listed as rare. The ornamental use of S. formosus has untapped commercial potential as a flowering indoor pot plant, an outdoor bedding plant for shade and as a cut flower for the vase, all of which are limited by a five-month eco-dormancy period during the late autumn and all through the cold season in the short-day winter months. Viable commercial production will require cultivation techniques that produce flowering plants all year round. This study investigated the effectiveness of applying root zone heating to S. formosus plants grown in deep water culture hydroponics during the eco-dormancy period in preventing abscission layer formation and in encouraging flowering and assessed the growth activity response of the plants. The experiment was conducted over eight weeks during the winter season in the greenhouse at Kirstenbosch Botanical garden in water reservoirs, each maintained at five different experimental temperature treatments (18, 22, 26—control, 30 and 34 °C) applied to 10 sample replicates. The results showed that the lowest hydroponic root zone temperature of 18 °C had the greatest effect on the vegetative growth of S. formosus, with the highest average increases in fresh weight (1078 g), root length (211 cm), overall leaf length (362 cm) and the number of newly leaves formed (177 = n), all noted as statistically significant when compared with the other water temperature treatments, which yielded negative results from reduced vegetative growth. Findings from the study also revealed that while all heated solutions significantly prevented the formation of abscission layers of S. formosus, they had a less significant effect on inflorescence formation, with only 18 °C having the greatest positive effect on flower development.

Biochar and DMPP Regulated Root-Zone CO2, N2O and CH4 Emissions of Soil-Ridged/Substrate-Embedded Cultivation Sweet Pepper in Chinese Solar Greenhouse

Northern China is a major production area for off-season vegetables in Chinese solar greenhouse. Usually, greenhouse gas emission flux and coefficient in Chinese solar greenhouse are higher than those in the open field. The reason for this phenomenon is heavy nitrogen (N) fertilization (esp. chemical N and organic manure N) and frequent irrigation during year-round cultivation. A novel substrate cultivation method for vegetable production in Chinese solar greenhouse, called soil-ridged/substrate-embedded cultivation (SSC), was put forward to reduce environmental pollution and increase use efficiency of nutrients. To clarify the characteristics of SSC root-zone greenhouse gas emissions, and the regulation effects of biochar and DMPP addition, five treatments were designed in Chinese solar greenhouse under the same nitrogen application level, including soil-ridge cultivation (SC, as a control), SSC (peat: vermiculite: perlite (v/v = 2:1:1), SSC-B50% (biochar: vermiculite: perlite,v/v = 2:1:1), SSC-B25% (biochar: peat: vermiculite: perlite, v/v = 1:1:1:1), and SSC-DMPP (SSC supplemented with 1% (w/w) DMPP of N fertilizer). Results showed that SSC improved fruit yield of sweet pepper of by 10.99% compared to SC. SSC-B50% and SSC-DMPP significantly improved sweet pepper growth compared to SSC. Moreover, SSC-DMPP increased sweet pepper yield by 10.30% compared to SSC treatment, while SSC-B50% and SSC-B25% treatments lowered the yield by 47.1% and 13.7% separately. Five treatments presented various root-zone temperature features. Also, substrate pH of SC, SSC-B50%, and SSC-B25% is alkaline, while SSC and SSC-DMPP treatments is acidic. Besides, the Global Warming Potential was significantly mitigated in the SSC cultivation compared with the SC. Similarly, the greenhouse gas intensity decreased from 0.074 to 0.038 kg CO2-eq kg− 1 yield. Compared with the SSC treatment, cumulative N2O emissions were significantly reduced in the SSC-DMPP treatment. The greenhouse gas intensity also decreased from 0.038 to 0.033 kg CO2-eq kg− 1 yield. Thus, we concluded that SSC was a promising method characterized with reduced greenhouse gas emissions and increased fruit yield. Application of DMPP in SSC cultivation significantly reduced N2O emissions. We recommend SSC method use in Chinese solar greenhouse with DMPP addition in substrate to optimize greenhouse gas mission.