Search Results

Manipulation of the electrical conductivity (EC) of the hydroponic nutrient solution has been studied as an effective method to enhance flavor and nutritional value of tomato fruit. The objective of this research was to quantitatively understand the accumulation of lycopene, soluble sugars, and the degradation of chlorophyll in fruits as affected by EC and EC application timing relative to fruit ripeness stages. `Durinta' tomato was grown hydroponically inside the greenhouse under two EC (2.3 and 4.5 dS·m^-1). The high EC treatment began immediately after anthesis (HEC treatment) or 4 weeks later (DHEC treatment), when fruits had reached maximum size, but still were green. Fruits were harvested weekly beginning 2 weeks after anthesis, until they reached red ripe stage. The chlorophyll concentration in tomato fruits showed no difference between treatments when compared at the same ripeness stages. The lycopene concentration of red ripe tomato fruits in HEC and DHEC treatments was 29% greater than that in low EC control (LEC treatment). However, there was no significant difference in lycopene concentration between HEC and DHEC. Both DHEC and HEC increased total soluble solid concentration (TSS) of red ripe tomato fruits compared with those grown in LEC; while the DHEC showed an increase of fruit TSS of 12%, the HEC had a greater enhancement of TSS of 19%. In addition, the fruit ripeness was accelerated under high EC, regardless of the timing of treatment. High EC treatment at early and mature green fruit developmental stages enhanced both fruit TSS and lycopene concentration; however, the nutrient solution EC effect on lycopene concentration was not dependent on the time of application during fruit development.

Five cultivars (Blitz, Mariachi, Quest, Rapsodie, and Trust) of tomato (Solanum lycopersicum) were grown hydroponically in a greenhouse to determine photosynthetic and transpirational responses to three electrical conductivities (EC) [2.3 (control), 4.8, and 8.4 dS·m⁻¹] of inflow nutrient solution. Leaf photosynthetic light response curves were measured during the early vegetative growth stage for cv Mariachi and Rapsodie and during the reproductive growth stage for all five cultivars. Leaf transpiration rate and leaf conductance were measured for all five cultivars in both stages. During the vegetative growth stage, high EC treatment of 8.4/14.3 dS·m⁻¹ inflow/efflux solution reduced leaf conductance and transpiration rate by 28% and 29%, respectively, compared with low EC treatment (2.3/5.9 dS·m⁻¹), regardless of cultivar. Effects of EC treatments on leaf photosynthetic light response curves were cultivar specific. For ‘Mariachi’, moderate EC (4.8/8.7 dS·m⁻¹) and high EC treatments in the vegetative growth stage reduced the maximum photosynthetic rate by 49% compared with the low EC treatment. However, for ‘Rapsodie’, the moderate EC treatment increased the maximum photosynthetic rate during the vegetative stage by 8% and 47% compared with low and high EC treatments, respectively. During reproductive growth stage, EC treatment did not significantly affect the transpiration rate, but high EC treatment reduced the leaf conductance by 15%, regardless of cultivar. Parameters of leaf photosynthetic response curves were affected by cultivar and EC treatment. Compared with the low EC treatment, the moderate EC treatment did not significantly affect the maximum photosynthetic rate of any cultivar except ‘Rapsodie’, which showed the greatest maximum photosynthetic rate in the moderate EC treatment. The results showed that the plant physiological response under elevated EC was cultivar and growth-stage specific, and increasing the inflow EC to the moderate level of around 4.8 dS·m⁻¹ during the reproductive growth stage would not negatively impact photosynthesis, transpiration, and leaf conductance of tomato plants, for all cultivars tested in the present experiment.

Plants produce various phytochemicals that are of nutritional and medicinal value to humans. Phytochemicals having antioxidant capacity are drawing increased interest from consumers. Population studies among Americans have consistently demonstrated inadequate consumption of fruit and vegetables. Improving intake of fruit and vegetables has been a major public health effort for many years with minimal success. Given this, it seems opportunistic to consider other approaches to enhance the nutritional quality of the American diet. One plausible approach is the development of fresh produce containing a greater concentration of phytochemicals known to improve health, thus while consuming fewer servings of produce, Americans would still have significant exposure to health-promoting food constituents. Controlled environments provide a unique opportunity to modify the concentrations of selected phytochemicals in fruit and vegetables, yet practical information is limited regarding methods effective in optimizing antioxidant capacity. Our research at the University of Arizona Controlled Environment Agriculture Program has shown that application of moderate salt stress to tomato plants can enhance lycopene and potentially other antioxidant concentrations in fruit. The increase in lycopene in response to salt stress in the tomato fruit was shown to be cultivar specific, varying from 34% to 85%. Although the specific biological mechanisms involved in increasing fruit lycopene deposition has not been clearly elucidated, evidence suggests that increasing antioxidant concentrations is a primary physiological response of the plant to the salt stress. Another experiment showed that low temperature during postharvest increased antioxidant capacity of tomato fruit while it maintained the lycopene concentration. More detailed study in this area is needed including accumulation of antioxidant phytochemicals as affected by environmental conditions during the cultivation and the postharvest.

Abstract

Suspension-cultured pear (Pyrus communis ‘Bartlett’) cells cold-acclimated during exposure to 2°C. Cold acclimation was accompanied by changes in soluble extracellular polysaccharides and in the deposition of callose in the cell wall. Release of a relatively small neutral polysaccharide into culture medium was increased at 2°. However, low temperature decreased the extracellular accumulation of a larger molecular weight (M _r) pectic polysaccharide. The reduced amount of pectic polysaccharide may have been the result of both a low-temperature-enhanced degradation of existing polysaccharide and an inhibition of new synthesis or secretion. The effect of low temperature on callose deposition was observed using an aniline blue fluorescent staining procedure. Pear cells held at 2° showed far more intense staining than those at 22°, indicating increased deposition of callose or other β-1,3-glucans at the cell surface during cold acclimation.

Temporary immersion culture vessels were modified to culture Protea cynaroides L. microshoots on semisolid growth medium. The effects of different ventilation treatments and sucrose concentrations on the vegetative growth and physiological characteristics of P. cynaroides L. microshoots were investigated. Three ventilation treatments were used: microshoots were either ventilated naturally or forced ventilated for 2 minutes/2 hours or 2 minutes/4 hours. In addition, two sucrose concentrations were used in the growth medium: 30 and 10 g·L⁻¹. Significant interaction effects were found between ventilation and sucrose in the number of shoots formed. When cultured on growth medium with 10 g·L⁻¹ sucrose, microshoots force-ventilated for 2 minutes/2 hours produced significantly higher number of shoots than those naturally ventilated or force-ventilated for 2 minutes/4 hours. In the 30 g·L⁻¹ sucrose treatment, no significant differences in shoot numbers were observed among all ventilation treatments. The highest leaf areas were found in microshoots cultured in the 2 minutes/4 hours forced ventilation treatment, which were significantly higher than microshoots in the other ventilation treatments, irrespective of the sucrose concentration. Chlorophyll content was significantly higher in leaves of microshoots that were cultured in 30 g·L⁻¹ sucrose compared with those grown in 10 g·L⁻¹ sucrose in all ventilation treatments. Analysis of chlorophyll fluorescence of the leaves revealed that the F _v/F _m value of microshoots grown on 30 g·L⁻¹ sucrose and force-ventilated for 2 minutes/4 hours was significantly higher than those naturally ventilated in the same sucrose treatment. Overall, the use of 30 g·L⁻¹ sucrose in combination with 2 minutes/4 hours ventilation provided the best conditions for culturing P. cynaroides microshoots. This study demonstrated that these modified temporary immersion culture vessels can be used as a forced ventilation system to culture P. cynaroides microshoots and promote vegetative growth as well as improve their photosynthetic characteristics. The system described here introduces a simple and novel method of converting commercially available temporary immersion systems into force ventilation systems.

The development of calyxes in ‘Korla’ fragrant pear is influenced by hormones. This study was conducted to investigate the effects of different plant growth regulators on the endogenous hormone content of young ‘Korla’ fragrant pear fruit. The hormone contents [indoleacetic acid (IAA), gibberellin acid (GA₃), and abscisic acid (ABA)] of young ‘Korla’ pear fruits treated with water, IAA, and triiodobenzoic acid (TIBA) were determined by high-performance liquid chromatography, and the relationship between the content and ratio of endogenous hormones and calyx abscission in ‘Korla’ fragrant pear was explored. The results showed that the rate of calyx abscission in the ‘Korla’ pear fruits treated with TIBA was significantly higher than that of fruits treated with water and IAA, and that of fruits treated with water was significantly higher than that of fruits treated with IAA. The GA₃ content was higher than the IAA and ABA contents during each period. The IAA content of the stalk was higher than that of the calyx tube and flesh. The GA₃ and ABA contents of the calyx tube were higher than those of the stalk and flesh. The IAA and GA₃ contents of the first order were higher than those of the fourth order. The ABA content of the fourth-order fruit was higher than that of the first order. The (IAA+GA₃)/ABA in the calyx tube was significantly higher than that in the flesh and fruit stalk. After IAA treatment, the IAA, GA₃, and ABA contents of the first-order calyx tube increased by 47.7%, 17%, and 31.6%, respectively, whereas those of the fourth-order calyx tube increased by 65.3%, 39.9%, and 33.2%, respectively. After TIBA treatment, the IAA, GA₃, and ABA contents of the first-order calyx tube increased by 46.1%, 36.5%, and 50.0%, respectively, the IAA content of the fourth-order tube decreased by 25.5%, and the GA₃ and ABA contents increased by 22.0% and 12.2%, respectively. The IAA, GA₃, and ABA contents of the flesh and fruit stalk did not significantly differ from those in the calyx tube. The results indicated that spraying IAA during flowering promoted calyx persistence, whereas spraying TIBA promoted calyx abscission. These findings provide certain theoretical references and practical criteria for improving the quality of ‘Korla’ fragrant pear.

We investigated the effects of different planting seasons and gibberellic acid treatments on the growth and development of Gypsophila paniculata to explore new approaches to controlling the flowering period. Four different cultivars were selected and continually planted in July, September, and November in the low-latitude and high-altitude region of Kunming, China (25° N, 102° E). Results showed that the vegetative growth and flowering time of Gypsophila paniculata were prolonged and postponed when the planting time was delayed. Specifically, ‘My Pink’ showed 20% and 80% rosette rates when grown in autumn and winter, respectively, thus indicating that Gypsophila paniculata is sensitive to planting time. Moreover, GA₃ treatment not only can significantly promote vegetative growth but also can stimulate early flowering and suppress the occurrence of rosettes during winter. This is more specific to ‘My Pink’, which showed 40% and 80% reductions in rosette rates with four and eight GA₃ treatment applications, respectively. Our study showed that seasonal variations in the growth and development of Gypsophila paniculata and GA₃ treatment can effectively stimulate early flowering and suppress rosettes during winter.

This study investigated the effects of different sucrose, ventilation, and paclobutrazol (PBZ) treatments on the growth of potato plantlets cultured in modified temporary immersion culture vessels. Temporary immersion culture vessels were modified to enable the plantlets to be cultured on semi-solid growth medium and provided with forced ventilation. The plantlet responses to two sucrose concentrations (15 g⋅L⁻¹ and 30 g⋅L⁻¹) in combination with two forced ventilation treatments (5 min/2 h and no ventilation) and three PBZ concentrations (0, 0.2, and 0.4 mg⋅L⁻¹) were studied. Shoot growth was severely inhibited by PBZ in the growth media, whereas leaf formation was promoted by ventilation irrespective of the PBZ concentration. In nonventilated vessels, it is noteworthy that PBZ was able to increase the number of leaves formed in plantlets grown on medium supplemented with 30 g⋅L⁻¹ sucrose, but not on medium with 15 g⋅L⁻¹ sucrose. In growth media without PBZ, a high percentage of potato plantlets was able to produce secondary axillary shoots when provided with 30 g⋅L⁻¹ sucrose. However, their ability to produce secondary shoots was reduced when PBZ was included in the growth medium, particularly those with 15 g⋅L⁻¹ sucrose. Plantlets grown in ventilated culture vessels combined with 30 g⋅L⁻¹ sucrose in the growth medium produced more than three times more shoots than the other treatments. Under ex vitro conditions, plantlets that had been grown in ventilated vessels had fewer leaf deaths, and the inclusion of PBZ in the growth media further reduced the number of dead leaves. Findings of this study showed that PBZ had a key role in the responses of potato plantlets to ventilation and sucrose treatments, as well as their tolerance to ex vitro conditions. The modified temporary immersion system can be used for the in vitro culture of potato plantlets on semi-solid medium and provide forced ventilation to improve their growth.

Simple sequence repeat (SSR) markers are valuable for genetic and breeding applications, but SSR resources for the ornamental genus chrysanthemum (Chrysanthemum ×morifolium Ramat.) are still limited. Expressed sequence tags (ESTs) are sources of SSRs that represent an opportunity to develop SSRs to accelerate molecular breeding in chrysanthemum. In total, 4661 SSR loci were identified from 3823 SSR-containing unigenes in the chrysanthemum transcriptome with an average of one SSR per 6.98 kb. Of these SSR sequences, trinucleotide repeats (30.0%) predominated, followed by dinucleotide repeats (17.9%). In total, 1584 primer pairs were subsequently synthesized. By screening the parents and six individuals of the F₁ progeny, 831 (52.5%) valid EST-SSR markers were identified, of which 361 (43.4%) were polymorphic. The annotation of unigenes containing polymorphic SSRs indicated that 330 (93.5%) demonstrated significant homology to other plant protein sequences. Twenty-five polymorphic EST-SSR markers were further selected for transferability analysis and exhibited 93% amplification in six Ajania species and six other Chrysanthemum species. Based on genotyping of the 59 samples, neighbor-joining analysis revealed six phylogenetic groupings, which was confirmed by population structure analysis and principal component analysis (PCA). Phylogenetic relationships among the 59 samples revealed by SSRs were highly consistent with the traditional taxonomic classification of Chrysanthemum and Ajania. The polymorphism information content (PIC) values ranged from 0.29 to 0.86, with a mean of 0.67, indicating high levels of informativeness. This research reveals the SSR distribution characteristics of chrysanthemum and provides a large number of new EST-SSR markers for further genetic diversity studies, genetic mapping, and molecular marker-assisted selection breeding for chrysanthemum.