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Greenhouse experiments were conducted in 2017 and 2018 to investigate quantitative relationships between tomato yield parameters and deficit irrigation at different growth stages. Tomato plants received one of three irrigation treatments (full irrigation, 2/3, and 1/3 full irrigation) at flowering and fruit development (stage 2) and at fruit maturation (stage 3); no deficit irrigation treatments were applied at stage 1 during either season. We used linear regression to investigate how well the yield parameters such as whole-plant yield (Y), single-fruit weight (y), fruit diameter (D), and length (L) were correlated with seasonal evapotranspiration (ET) under different deficit irrigation treatments. Six water–yield models (Blank, Jensen, Singh, Stewart, Minhas, and Rao models) were used to predict the tomato yield parameters with deficit irrigation at different growth stages. The results showed that deficit irrigation at each growth stage significantly decreased ET, Y, y, L, and D, but not T1 (2/3 full irrigation at flowering and fruit development). T1 produced higher water use efficiency (WUE) with no significant decrease in yield parameters, indicating that an acceptable balance between high WUE and yield can be obtained with an appropriate water deficit at stage 2. Relative Y, y, D, and L increased linearly as relative seasonal ET increased. Water deficit sensitivity indexes calculated by the six different water–yield models showed that Y, y, D, and L were more sensitive to water deficit at stage 2 than at stage 3. The values of Y calculated by the Minhas and Singh models were similar to the observed values. The Minhas model provided good estimates of L and D, and the Blank model is recommended for calculating y when there is a water deficit at different growth stages. The water–yield models can be used to optimize irrigation water management and provide a sound basis for efficient tomato production.
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.
Molecular markers were used to study the genetic diversity, structure, and relationship of Juglans L. with nine populations (five from Juglans regia L. and four from Juglans sigillata Dode) in central and southwestern China. A moderate level of genetic diversity was observed at the population level with the number of effect alleles per locus (A E) ranging from 1.75 to 3.35 (average 2.39) and the proportion of polymorphic loci (P) equaling 100.0%. The expected heterozygosity (H E) within populations ranged from 0.389 to 0.687, and the average was 0.525. The proportion of genetic variation presented among populations accounted for 18.6% of the total genetic diversity. The overall gene flow (N m) among populations equaled 1.10. The unweighted pair-group method using arithmetic averages (UPGMA) clustering and the Mantel test showed that genetic distances among the nine populations are in a good agreement with their geographic distribution, supporting the viewpoint that J. regia and J. sigillata belong to one species. We suggest that the central area of the southwestern mountain regions of China could be considered as a priority for walnut genetic resource conservation.
To investigate the quantitative response of tomato yield and fruit quality to deficit irrigation applied at different growth stages, greenhouse experiments were conducted in 2017 and 2018. Three irrigation treatments (full irrigation and two-thirds or one-third of full irrigation) were applied to greenhouse-grown tomato plants at flowering and fruit development (stage 2) and at fruit maturation stage (stage 3). Grey relational analysis (GRA), the technique for order preference by similarity to an ideal solution (TOPSIS), and principal components analysis (PCA) were used to calculate the comprehensive fruit quality indexes, and combinatorial evaluation method was determined. The results showed that deficit irrigation significantly reduced evapotranspiration (ET) and tomato yield and that relative yield had a negative linear correlation with relative seasonal water deficit (1−ETi/ETc). However, deficit irrigation improved fruit quality, especially at stage 2. Total soluble solids, the total soluble sugar concentration, the sugar-to-acid ratio, and vitamin C in the tomatoes all increased significantly in plants that were deficit irrigated compared with fully irrigated plants, while organic acids and lycopene decreased in both years. There were linear correlations between fruit quality parameters and 1−ETi/ETc. The comprehensive quality index derived from GRA and PCA is reliable, and the comprehensive quality indexes given by GRA, PCA, and a combination of GRA and PCA showed positive linear correlation with 1−ETi/ETc. The comprehensive quality ranking showed that in both years, F2/3M1 (two-thirds full irrigation at stage 2) gave a better result and CK (full irrigation) the worst. An appropriate water deficit at the flowering and fruit development stage, which results in a trade-off between acceptable yield and improved fruit quality, is recommended. Our results provide a sound basis for tomato production that has a desirable balance between high yield and high fruit quality.
Herbaceous peony is a perennial flowering plant with strong environmental adaptability and may be a good candidate for culture in arid areas. In this study, the physiological and biochemical responses of two herbaceous peony cultivars to different soil moisture gradients in pots were assessed by analyzing changes in 13 stress-related indices. The drought damage index (DDI) and the contents of malondialdehyde (MDA), soluble sugar, proline, and abscisic acid (ABA) generally increased as drought stress intensified, whereas leaf relative water content (LRWC) decreased, and the contents of soluble protein, indole-3-acetic acid (IAA), the ratio of IAA and ABA, and the activities of four antioxidant enzymes fluctuated. For the leaves, a positive correlation was found between DDI and superoxide dismutase (SOD), MDA, soluble sugar, proline, ascorbate peroxidase (APX), and ABA, but it was negatively correlated with LRWC, peroxidase (POD), and catalase (CAT). In fibrous roots, DDI was positively correlated with MDA, soluble sugar, proline, soluble protein, and ABA but was negatively correlated with SOD, CAT, APX, and IAA/ABA. Principal component analysis and subordinate functions were used to evaluate drought resistance of the two cultivars, with ‘Karl Rosenfield’ showing greater resistance to drought than ‘Da Fu Gui’.
Big fruit size and nice red pigmentation combined with good flavor should be the major target for red-fleshed kiwifruit (Actinidia spp.) breeding programs. Genetic diversity and plant characteristics were evaluated on a set of kiwifruit accessions with predominantly red flesh to identify the superior individuals for further breeding or study of commercial application. The leading phenotypic characters varied widely among the accessions. Accession R reached average fruit weight ≈100 g, whereas it ranged from 43.15 to 84.71 g for the other accessions. Fruits of L and Q were flatter in shape than the others. The core volume accounted for fruit proportions ranging from 2.33% to 11.42%. ‘Chuhong’, ‘Honghua’, and K exhibited a round fruit apex, whereas most others showed a depressed apex. R, L, and Q had the highest a* values in the inner pericarp and also the most appealing visual coloration. Results revealed significantly higher soluble solid content (SSC), total sugar, and sugar/acid ratio in Q, R, and L. The 12 pairs of simple sequence repeat (SSR) markers were successfully used to characterize the genetic variability and confirm true-to-type identity for four accessions. However, the limited number of markers had no ability to discriminate among the other 11 accessions. Based on additional 28 SSRs, six of the indistinguishable accessions were confirmed to be genetically different, and three seemed to belong to the same clone vine. The results demonstrated that application of SSR data could improve the efficiency of identifying red-fleshed kiwifruit germplasm.
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.
Leaves of Begonia semperflorens accumulate anthocyanins and turn red under low temperature (LT). In the present work, LT increased H2O2 content and superoxide anions production rate, causing significant increases in the activities of enzymes and contents of reduced components involved in the ascorbate-glutathione cycle (AsA-GSH cycle). As a result, LT-exposed seedlings increased the expression of genes involved in anthocyanin biosynthesis, and accumulated anthocyanin. Based on LT condition, application of N,N'-dimethylthiourea (DMTU) decreased reactive oxygen species (ROS) content, and unbalanced the AsA-GSH-controlled redox homeostasis. As a result, seedlings in the LT + DMTU group did not accumulate anthocyanin. Our results suggest that ROS may act as an important inducer in LT-induced anthocyanin biosynthesis.
Light-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and more flexible and feasible spectral control compared with other artificial lighting. The combined effects of red and blue (RB) LED with or without green (G) LED light and white LED light on lettuce (Lactuca sativa L.) growth and physiology, including nitrate content, chlorophyll fluorescence, and phytochemical concentration before harvest, were investigated. Continuous light exposure at preharvest can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants. Nitrate accumulation is dependent on the spectral composition and duration of treatment: lettuce exposed to continuous RB (with or without G) LED light with a photosynthetic photon flux (PPF) of 200 µmol·m−2·s−1 exhibited a remarkable decrease in nitrate content at 24 hour compared with white LED light treatment at the same PPF. In addition, RB LED light (R:B = 4:1) was more effective than white LED light at the same PPF in facilitating lettuce growth. Moreover, continuous LED light for 24 hours significantly enhanced free-radical scavenging activity and increased phenolic compound concentrations. We suggest that 24 hours continuous RB LED with G light exposure can be used to decrease nitrate content and enhance lettuce quality.