ASHS 2024 Conference

Crop seed germination is a critical factor in food production. Germination traits vary between different vegetables and between cultivars of the same vegetable. Traits such as germination proportion and the rate and uniformity of germination also contribute to the success of vegetable cultivars to regional temperature averages and regimes. Temperature is a major abiotic factor in seed germination, and selection of seed varieties suited for local temperatures is important to successful crop establishment. Here we aim to model the germination traits of several Korean and North American vegetable cultivars in relationship to temperature. We hypothesize that a model based on time and temperature will represent germination traits across multiple cultivars and species of vegetable. Additionally, we hypothesize that predicted germination traits will be similar within species but will vary between cultivars of the same species based on the regional temperature norms. Eleven vegetable cultivars including two corn, four radish, two pepper, and three onion, were germinated in growth chambers set at 5°C intervals between 5 and 40°C with a 12 hour photoperiod. Germination, defined by radicle emergence equal to the length of the seed, was monitored and recorded daily. Two modeling approaches were used. 1) A time to event model using the drcSeedGerm package in R was used to determine maximum germination proportion (Pmax), germination rate at 50% germination (GR50), and uniformity. 2) A 12-parameter compartmental temperature and time model was implemented, parameterized, and validated in the Cropbox modeling framework. Results show differing temperature responses in germination traits. Additionally, high uniformity was observed in most varieties within the optimal temperature range. The optimal temperature for germination was broad for the vegetable cultivars tested here, with a rapid decrease in Pmax at high and low temperature extremes, except in onions, which showed high Pmax even at 5°C, and a gradual decline above 25°C. All cultivars showed decreased Pmax at 40°C. A time to event model was able to predict germination traits in several crop species. The compartmental model was better equipped to handle heat induced seed degradation but was less parsimonious for determining germination probability and germination rate related parameters. Modeling crop germination traits can provide important context for selecting appropriate cultivars for local climates. A thermal time to event model and a compartmental model both provide potential frameworks for modeling germination traits of diverse vegetable species.

Pawpaw (Asimina Triloba) is a temperate species of tropical Annonaceae plant family native to the United States. They are small to medium-sized deciduous trees that bear unique and flavorful fruit. Pawpaw fruits are used in various culinary products such as jam, bread, ice cream, cookies, and even to produce brandy. Additionally, they contain antioxidants and acetogenins, which are currently being researched for their potential in cancer treatment. Fruit sets may be limited in some cultivars due to pawpaw flowers being protogynous and self-incompatible, blooming at various stages of development from late March to April. Consequently, the role of insects in pollination is crucial for increasing fruit production. To address this gap in research, this study aims to identify the different insect orders that visit both flowering and non-flowering branches of two distinct pawpaw cultivars (Sunflower and Susquehanna), along with their respective abundances. Ten trees from each pawpaw cultivar were selected to investigate the various pollinator types. In a completely randomized design, 40 wire cage traps with tangle trap adhesive were placed on both the flowering and non-flowering branches of each chosen cultivar. After 18 days of the flowering period, the traps were collected, and the insects captured were identified by order and counted. The data were analyzed using R software (R 4.3.2) and subjected to a one-way ANOVA with flower and non-flower of each cultivar, a two-way ANOVA, Least Significant Difference (LSD) means separation, with flowers and cultivars as the treatments. In 2023, ‘Sunflower’ had significantly more Dipterans and total insects (p-value: 0.3373 NS and 0.3740 NS). In comparison, ‘Susquehanna’ had significantly more Coleopterans (p-value: 0.40525 NS), and in ‘Susquehanna’, coleopterans had significantly more in the flower-branch (p-value: 0.0255*) for 2023. Additionally, data for 2024 will also be reported and will include additional data on insects observed inside the female receptive and matured male flowers from each cultivar.

The morphological characteristics of the xylem elements influence water ascent in the plants. Few models determine the physical process of water movement in the vascular system of plants based on the hydraulic architecture. This study aims to determine the anatomical characteristics of the xylem and potential hydraulic conductivity at different positions along of tomatoes (Solanum lycopersicum; Solanaceae). The xylem vessels characteristics were examined in four internodes using three segments in each internode. The analogy between Ohm’s law and Hagen-Poiseuille was used to determine the hydraulic conductivities. A successive decrease in the mean vessel diameters from the bottom to the top stem was observed, with a significant difference between successive decrease in the mean vessel diameters from the bottom to the top stem was observed, with a significant between different percentages of height. The variation of the hydraulic conductivity along the useful length of tomato allowed a better application of the Hagen-Poiseuille equation.