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Boris Timofeevich Matienko (1929–2004) was a respected plant anatomist and physiologist in Soviet Moldova. Matienko’s research was primarily on the growth, development, and senescence of cucurbits, as well as apples, plums, and other vegetable crops. His studies provided a wealth of information to those interested in the anatomic structure of pumpkins, squash, gourds, watermelon, and minor Cucurbitaceae. Using insightful and detailed descriptions, he depicted cellular changes of the fruit during development, aging, and senescence. Practical experiments on storage corroborated his detailed microscope studies. Matienko worked during a time when the problems of the agriculture sector in Moldova were immense and varied, and he faced structural and societal challenges that underscore his scientific accomplishments. The quality of cucurbits grown in Moldova and the region improved as a result of this research. He was widely respected by colleagues and the scientific community, and his work continues to provide insight to researchers of these important crops.

Open Access

Cannabis (Cannabis sativa) grown for flowers containing cannabinoids requires all female plants, which are susceptible to seed set from exposure to pollen. Created triploids demonstrated reduced seed production compared with diploids in field and greenhouse studies in which plants were challenged with pollen from males. In the field, seed production as a percent of floral biomass ranged from 6.7% to 18.0% for triploids and from 52.6% to 57.1% for diploids. The photoperiod-insensitive triploid genotype ‘Purple Star’ × ‘Wilhelmina’ had 98.5% fewer filled (containing a developed embryo) seeds than the photoperiod-insensitive diploid genotype ‘Tsunami’ × ‘Wilhelmina’. In the greenhouse, triploid ‘Wife’ had 99.5% fewer filled seeds than diploid ‘Wife’. Plant growth and flower production were similar with eight triploid and seven diploid genotypes evaluated over three greenhouse studies. There were a few superior triploid and diploid genotypes; however, their performance was more likely attributable to the parental cultivar combination than ploidy level. The optimal cross direction for producing triploid seed in large quantities is tetraploid × diploid because the diploid × tetraploid cross exhibits triploid block caused by endosperm paternal excess. Colchicine-induced tetraploid parent plants should be tested over a prolonged period to eliminate cryptic chimeral mixoploids or tetraploid plants should be derived from seed produced by crossing two colchicine-induced putative tetraploid plants to ensure that seeds from tetraploid × diploid crosses will be triploid. The latter approach is necessary for photoperiod-insensitive cultivars because a prolonged period of ploidy testing is not possible for these plants. These findings indicate that triploid plants have significantly reduced fertility and are a suitable alternative to diploids in situations in which pollen exposure is possible.

Open Access

Oncidesa Gower Ramsey ‘Honey Angel’ is a cut flower crop of high economic value worldwide. The regulation of flowering is important for cut flower production scheduling. However, its flowering transition mechanism is still unclear. Oncidesa usually flowers at the end of the growth cycle for each pseudobulb; this timing is probably related to carbohydrate accumulation. During this study, we investigated the carbohydrates in the pseudobulbs from juvenile plants to adult plants and compared the carbohydrates in flowering and nonflowering adult plants. The current pseudobulb and back pseudobulbs of the plants at 0, 0.5, 1.0, 1.5, and 2.0 years after having been moved out of the tissue culture flask were collected. The first pseudobulb formed at 0.5 years, and plants had fulfilled four growth cycles and flowered at 2.0 years. Each successive current shoot grew larger and the back shoot number progressively increased after each new growth cycle. The concentration of total soluble sugars in the current shoot increased from 5.5% of dry weight at 0.5 years to 20.2% of dry weight at 1.5 years. Conversely, the starch concentration decreased in the current pseudobulb as the plants matured. The starch concentration in the back pseudobulbs did not change when the plant grew a new shoot. The starch concentrations in the back pseudobulbs ranged from 33.2% to 57.5% of dry weight, but the combined content of starch in all of the back pseudobulbs increased significantly from 168 mg at 0.5 years to 4608 mg at 2.0 years because of the increasing number of back shoots. The starch in the first back pseudobulb of the nonflowering adult plants accounted for 18.0% of dry weight, which was lower than that of the flowering plants (48.3%). There was no significant difference in total soluble sugars in the current pseudobulb of the nonflowering and flowering plants. Overall, we revealed that the increase in the back shoot number increased the total amount of reserve carbohydrates as the plant reached reproductive maturity. A low starch level was observed in nonflowering adult plants. In both cases, flowering plants had higher starch storage in the back pseudobulbs, suggesting that carbohydrates might regulate the flowering of Oncidesa Gower Ramsey ‘Honey Angel’.

Open Access

The production of melons (Cucumis melo L.) in greenhouses relies on pollination. Extreme temperature and insufficient light reduce not only flower visitation by pollinators but also pollen viability, resulting in inefficient pollination. In this study, we investigated the effects of forchlorfenuron [(N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU)] on the fruit setting and growth of oriental melons (C. melo L. var. makuwa Makino). The primary objective was to devise a new strategy for the management of oriental melons. Treatment with 5 mg·L−1 CPPU a day before flowering (T1), on the day of flowering (T2), and a day after flowering (T3) increased the fruit setting rate (by 20.1% to 30%) in melons subjected to artificial pollination (AP) or no pollination (NP) compared with the rate in those subjected to only artificial pollination without CPPU (CK). CPPU treatment induced unfertilized seeds; in addition, a tendency toward parthenocarpy was noted. The highest fruit setting rate (∼95%) was noted in plants subjected to the following treatments: AP+T1 and NP+T3. The rates of abnormal fruit formation decreased from 45.2% of CK group to 9.4% in plants subjected to AP+T1 and to 19.4% in those subjected to NP+T3. Elevated exogenous concentrations of CPPU markedly increased fruit weight. Plants subjected to NP+10 mg·L−1 CPPU bore the heaviest fruits (541.0 g), which were heavier than those borne by plants subjected to AP+10 mg·L−1 CPPU. CPPU treatment reduced the fruit cavity ratio in a concentration-dependent manner from 47.3% to 33.6% and increased the pulp thickness from 1.5 to 2.5 cm. Notably, supplementary CPPU treatment exerted no significant effects on fruit traits. Regarding taste, inconsistent results were obtained for sugar accumulation. Although the content of cucurbitacin B increased immediately after the initial CPPU treatment, it markedly decreased after 15 days of CPPU treatment. Therefore, mature melons did not have a bitter taste.

Open Access

In the absence of controlled sufficiency studies, foliar interpretations for many horticultural crops are based on survey concentrations from small data sets. In addition, both survey and sufficiency ranges provide little interpretation regarding zones that are above or below the concentration range deemed “sufficient.” While providing a critical initial set of ranges, it was based on a limited set of data and therefore improvements in interpretation of data are needed. This study presents a novel method based on 1950 data points to create data-driven nutrient interpretation ranges by fitting models to provide more refined ranges of deficient (lowest 2.5%), low (2.5% to 25%), sufficient (25% to 75%), high (75% to 97.5%), and excessive (highest 2.5%). Data were analyzed by fitting Normal, Gamma, and Weibull distributions. Corresponding P values were calculated based on the Shapiro-Wilk test for normality for the Normal and Gamma distributions, and the Kolmogorov-Smirnov test was used for the Weibull distribution. The optimal distribution was selected based on the lowest Bayesian Information Criterion (BIC) value and visual fitness. The Weibull distribution best represented nitrogen, phosphorus, potassium, calcium, manganese, zinc, and copper, and the Gamma distribution best represented magnesium, sulfur, iron, and boron. Using the selected distributions, we propose a refined set of nutrient evaluation ranges for greenhouse-grown lettuce. These refined standards will aid growers and technical specialists in more accurately interpreting leaf tissue sample data.

Open Access

Hydroponic growing systems are advantageous for nutrient studies in which root data are important because they alleviate the laborious and time-consuming task of washing roots to remove soilless substrate particulates from them. However, the growing system should be optimized for the crop of interest. Our overall objective was to develop a protocol for hydroponic strawberry (Fragaria ×ananassa) production that provided growth equal to or better than soilless substrate. Plants were initially grown in perlite, sand, deep water culture (DWC), or a peat-based soilless substrate. Aboveground plant growth in DWC was similar to that of plants grown in the peat-based substrate and required minimal effort to harvest the entire root system. However, the pH of the DWC nutrient solution decreased to 4.0 ± 0.1 (mean ± SE) when plants were provided a modified strawberry (Yamazaki) nutrient solution with a ratio of nitrate (NO3 ) to ammonium (NH4 +) of 80:20. As a result, a subsequent trial was conducted to evaluate the buffering capacity of nutrient solutions with NO3 to NH4 + ratios of 0:100, 20:80, 50:50, 60:40, 80:20, or 100:0, with the addition of potassium bicarbonate (KHCO3). Up to 2.6 mM KHCO3 did not provide adequate buffering in nutrient solutions containing NH4 + (0:100 to 80:20 treatments), and nutrient solution pH decreased by ∼1.5 units every 2 to 3 days. The 100% NO3 nutrient solution, however, maintained a stable pH of 5.9 ± 0.1 when buffered with 0.8 mM KHCO3. Finally, 2(N-Morpholino)ethanesulfonic acid (MES) was evaluated as a potential buffering agent for DWC strawberry production. Plants were grown in a nutrient solution with a 60:40 ratio of NO3 :NH4 +. The buffering capacity of the nutrient solution increased as the MES concentration supplied increased from 1 to 5 mM, and the 5 mM MES treatment maintained a pH of 5.6 ± 0.2. In summary, strawberry plants can successfully be grown hydroponically in DWC, provided that nutrient solution pH is adequately managed. The addition of MES buffer provided better pH stability than KHCO3.

Open Access