Wenqian Zhang, Xiaoling Jin, Donglin Zhang, Minhuan Zhang, and Wen Xing
Paul C. Bartley III, Aziz Amoozegar, William C. Fonteno, and Brian E. Jackson
The heterogeneity of horticultural substrates makes basic physical characteristics, such as total porosity and particle density, difficult to estimate. Due to the material source, inclusion of occluded pores, and hydrophobicity, particle density values reported from using liquid pyknometry, vary widely. Gas pycnometry was used to determine the particle density of coir, peat, perlite, pine bark, and wood substrates. Further precision was examined by gas species and separation by particle size. The calculated particle densities for each material determined by He, N2, and air were relatively constant and varied little despite the species of gas used. Particle size affected the measured particle density of perlite and pine bark but was minimal with coir, peat, and wood. Reducing the particle size removed more occluded pores and the measured particle density increased. Given the small variability, the use of particle density values obtained by gas pycnometry provides repeatable, precise measurements of substrate material total porosity.
Ian K. Atkins and Jennifer K. Boldt
Supplemental lighting, temperature control, and CO2 enrichment can improve the productivity of greenhouse crops, but operating costs for greenhouse control systems to maintain environmental parameters at desired setpoints can be expensive. To balance operating costs with productivity, growers need to be able to predict how a crop will perform as a function of photosynthetic photon flux density (PPFD), CO2 concentration, and temperature. The objective of this study was to explore the response of net photosynthetic rate (Pn) to PPFD and CO2 concentration, for plants acclimated to different growth environment temperatures or light intensities. We measured Pn at all combinations of 14 irradiances and four CO2 concentrations of calibrachoa (Calibrachoa ×hybrida ‘Superbells Lemon Slice’), petunia (Petunia ×hybrida ‘Supertunia Mini Strawberry Pink Veined’), and verbena (Verbena ×hybrida ‘Superbena Royale Whitecap’) grown at three light intensities, and of geranium (Pelargonium ×hortorum ‘Maverick Red’), pepper (Capsicum annuum ‘California Wonder’), and sunflower (Helianthus annuus ‘Pacino Gold’) grown at three different temperatures. Sunflower, pepper, and geranium were fit to a model representing Pn as a function of PPFD, CO2 concentration, and leaf temperature. Photosynthetic light response curves, at each CO2 concentration, were fit for each species and growth environment using a nonrectangular hyperbola. These models can be used to identify multiple combinations of PPFD, CO2 concentration, and leaf temperature that would result in equivalent rates of photosynthesis, allowing the most cost-effective combination to be chosen.
Zienab F.R. Ahmed, Navjot Kaur, Sajid Maqsood, and Guillermo Schmeda-Hirschmann
The ‘Khenizi’ date palm is one of the most recognized date palm cultivars. It is commonly consumed at the Bisr, Rutab, and Tamr stages of ripening; however, the fruit has a short shelf/storage life at this stage of maturity even with refrigeration. Preharvest application of a natural elicitor chitosan (Ch) has been reported to have positive influences on quality and shelf life of many fruits; however, synergetic effects of Chand other natural elicitors have not been investigated. Therefore, this study aimed to investigate the synergistic effect of preharvest spray treatments with Ch 1% in combination with calcium chloride (Ca) 3% and salicylic acid (SA) 2 mm on ‘Khenizi’ date fruit quality and storage life. Fruit quality parameters, including physical and physiochemical characteristics, phytochemical content, and bioactive properties, were determined at harvest time and during cold storage at 2 °C for 60 days for 2 months. Our results revealed that a combination of these elicitors had significantly influenced the fruit quality during storage compared with control. For instance, Ch+SA and Ch+Ca+SA treatments improved total phenolic content (TPC), and the antioxidant activity at harvest and at specific times during the postharvest storage period. Furthermore, Ch+SA+Ca treatment significantly delayed senescence in treated fruits during cold storage for 45 days as compared with other treatments and the control. In addition, Ch+Ca-treated fruits had the lowest weight loss after 45 days of cold storage. Ch+SA treatment had the lowest microbial counts as compared with other treatments, including the control. The significance of this study is that it provides evidence that a combination of these elicitors has the potential to improve fruit quality at harvest, as well as during postharvest storage Future studies should be directed to fine tune the concentrations and combinations that may have commercial applications.
Yunfei Mao, Yijun Yin, Xueli Cui, Haiyan Wang, Xiafei Su, Lulu Zhang, Xin Qin, Yangbo Liu, Yanli Hu, and Xiang Shen
David’s peach [
William B. Miller, Wanxiang Lu, and Dongqin Tang
Although ethephon is commonly used as a plant growth regulator during commercial production of horticultural crops, information on its movement within plants is limited. In this study, we developed a method to detect ethephon in plant tissues, and determined ethephon localization and movement using tomato (Solanum lycopersicum L.) as a model system. Tissues were ground in an acidic buffer that preserved ethephon intact. Ethylene was released from the extracts by adding sodium hydroxide and was determined subsequently by gas chromatography. Ethephon was detected in leaves within 1 hour of application to peat-based root zones and within 10 minutes in hydroponics. In a pulse–chase experiment, ethephon levels increased initially, then decreased after the plants were returned to ethephon-free solutions. Ethephon was present in directly collected xylem fluid; fluid collected from petiole stumps (after leaf blade excision) had similar ethephon levels between the different petioles. Stem girdling had no effect on ethephon accumulation in leaves. Together, these data indicate ethephon is readily mobile in the xylem stream and provides insight into the commercial use of ethephon as a root zone-applied growth regulator.
Job Teixeira de Oliveira, Fernando França da Cunha, Rubens Alves de Oliveira, and Catariny Cabral Aleman Pina
Path coefficient analysis has been widely used to understand production better and determine the relationships between fruit and their constituents. This study evaluated the correlations between mass and other physical characteristics, and contributes to selecting cape gooseberry fruit. The attributes assessed were the total mass of the cape gooseberry fruit (TM) (fruit mass with husk), fruit mass (FM) (fruit mass without husk), husk mass (HM), husk length (HL), the largest transverse husk diameter (LD), fruit diameter (FD), and color of the husk (CH). Using path analysis, it was possible to verify directly that, among the physical components of the study, TM and FD have a direct and positive influence on FM. Fruit mass had a direct and negative correlation with HM, indicating that fruit with the heaviest husk (and green color) have not yet reached full maturation, nor reached their greatest mass. This result suggests that TM is strongly indirectly influenced by the HL, husk diameter, HM, and FD.
Zanzan Li, Jinyu Hu, Hang Tang, Liping Cao, Yuhang Chen, Qiaosheng Guo, and Changlin Wang
The spicas of Prunella vulgaris are widely used in the medical, beverage, and ornamental fields. Temperature and photoperiod are the two main ecological factors that determine the transformation of many plants from vegetative growth to reproductive growth. To explore the response of P. vulgaris flowering to temperature and photoperiod induction, we adopted vernalization long-day, vernalization short-day, nonvernalization long-day, and nonvernalization short-day treatments. The results showed that the morphology (total number of leaves, number of branches, number of leaves per branch, and branch length) of the vernalization treatment groups was significantly different from that of other nonvernalization groups, and the photosynthetic pigments, net photosynthetic rate, water use efficiency, stomatal conductance, intercellular CO2 concentration, and transpiration rate increased in the vernalization treatment group. However, the gibberellin 3 (GA3), indole-3-acetic acid and zeatin riboside (ZR) contents were significantly increased under the short-day treatments groups, and the results were the same for the expression of endogenous hormone synthesis genes, except for abscisic acid (ABA). The flowering-related genes soc1, elf3, svp, ga20ox, and cry1 were highly expressed under the vernalization short-day. Therefore, the induction of vernalization is more conducive to the increase in the photosynthetic rate. Temperature and photoperiod synergistically induced the synthesis and accumulation of starch, sugar, amino acids, and protein and affected the content of endogenous hormones and the expression of genes involved in their synthesis. GA3 and ZR had thresholds for their regulation of the flowering process in P. vulgaris, and high concentrations of ABA promoted flowering. Temperature and photoperiod coordinate the expression of the flowering-related genes soc1, elf3, svp, ga20ox, and cry1, thereby affecting the flowering process in P. vulgaris.
Richard P. Marini, Emily K. Lavely, Tara Auxt Baugher, Robert Crassweller, and James R. Schupp
‘Honeycrisp’ is a popular apple cultivar, but it is prone to several disorders, especially bitter pit. Previously reported models for predicting bitter pit are biased, indicating that the models are missing one or more important predictor variables. To identify additional variables that may improve bitter pit prediction, a study was undertaken to investigate the influence of canopy position, spur characteristics, and individual fruit characteristics on bitter pit development. ‘Honeycrisp’ trees from two orchards over 2 years provided four combinations of orchards and years. Fruits were sampled from spurs at different canopy positions and with varying bourse shoot lengths and numbers of fruits and leaves. Following cold storage, bitter pit was assessed in three ways: 1) bitter pit severity was recorded as the number of pits per fruit, 2) bitter pit was recorded as a binomial response (yes, no) for each fruit, and 3) the incidence of bitter pit was recorded as the proportion of fruit developing bitter pit. As a result of the high fruit-to-fruit variation, bitter pit severity was associated with canopy position or spur characteristics to a lesser extent than bitter pit incidence. Bitter pit incidence was generally greater for fruits developing on spurs with only one fruit and spurs from the lower canopy. Binomial data were analyzed with a generalized linear mixed model. Fruit harvested from trees with heavy crop loads, and those developing on spurs with multiple fruit and spurs with long bourse shoots had the lowest probability of developing bitter pit. Regardless of how bitter pit was assessed, bitter pit related positively to fruit weight (FW), but the relationship usually depended on other variables such as canopy position, fruit per spur, and leaves per spur. The advantages of fitting binomial data with logistic regression models are discussed.
Juan Guillermo Cruz-Castillo