Height control is important to produce compact vegetable transplants that are suitable for shipping and transplanting. Although abscisic acid (ABA) inhibits stem elongation, it can also induce other growth modifications. To optimize its application timing for effective height control, we examined age-dependent sensitivity of various growth variables to ABA in diploid ‘Summer Flavor 800’ and triploid ‘Summer Sweet 5244’ watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai]. Seedlings were sprayed once with 1.9 mm ABA at 25, 18, or 11 days before transplanting (DBT) or twice with 0.95 mm ABA at 25 and 18 DBT. The application rate was 0.55 mg ABA per plant with a spray volume of 0.61 L·m−2 (1.1 mL/plant). Only the single-spray treatment at 25 DBT (cotyledon stage) suppressed plant height by inhibiting petiole elongation. This effect was similar in both cultivars with 13% to 14% reductions at the transplanting stage compared with the untreated control. Undesirable growth modifications were also induced by ABA. In both cultivars, all ABA treatments caused 16% to 23% shoot biomass reductions mainly by inhibiting leaf expansion. Additionally, ABA treatments reduced stem diameter and root biomass in ‘Summer Flavor 800’. The double-spray treatment had similar growth-modulating effects as the single-spray treatments, except that it induced cotyledon abscission in ‘Summer Flavor 800’. These results suggest that although ABA applied at the cotyledon stage can reduce watermelon transplant height, the benefit is limited because of overall growth reductions, which can occur regardless of application timing. On the other hand, in triploid ‘Summer Sweet 5244’, moderate shoot growth delay by ABA may be of value as a growth-holding strategy when transplanting is delayed because of inclement weather at the time of field establishment. Importantly, field evaluations demonstrated that the growth modulation by ABA is only transient with no negative impact on marketable yield and fruit quality.
Shinsuke Agehara and Daniel I. Leskovar
Daniel I. Leskovar and Daniel J. Cantliffe
Shoot and root growth changes in response to handling and storage time in `Sunny' tomato (Lycopersicon esculentum Mill.) transplants were investigated. Transplants, 45 days old, were stored either in trays (nonpulled) or packed in boxes (pulled) for 0, 2, 4, 6, or 8 days at 5 and 15C. Also, 35-day-old nonpulled and pulled transplants were kept in darkness at 20/28C for 0, 1, 2, or 3 days. At SC, pulled transplants had longer and heavier stems, a higher shoot: root ratio, higher ethylene evolution, and lower root dry weight than nonpulled transplants. At 15C, pulled transplants had more shoot growth than nonpulled transplants. Nonpulled, initially 35-day-old transplants had heavier shoots and roots and higher (7.0 t·ha-1) yields of extra-large fruit than pulled transplants (4.1 t·ha-1), but there were no differences in the total yields of marketable fruits.
Daniel I. Leskovar and Daniel J. Cantliffe
Transplants produced with overhead or subirrigation and plants from direct seeding using primed or nontreated `Jupiter' bell pepper (Capsicum annuum L.) seeds were evaluated for growth and yield in the field for 3 years. Early in development, overhead-irrigated (01) transplants had more basal root elongation than subirrigated (SI) transplants; however, root growth differences caused by irrigation systems in the greenhouse were minimized during late ontogeny in the field. Basal, lateral, and taproot dry weights accounted for 81%, 15%, and 4% of the total for transplants and 25%, 57%, and 18% of the total for direct-seeded plants. Direct-seeded plants maintained a more-balanced root, stem, leaf, and fruit dry matter partitioning than transplants, which allocated more dry weight (per unit of root growth) to stems, leaves, and fruits. Over all seasons, transplants exhibited significantly higher and earlier yields than direct-seeded pepper plants, and total yields were similar between SI and OI transplants and between primed and nontreated seeds.
Daniel I. Leskovar and Daniel J. Cantliffe
ABA and drought stress were evaluated on growth morphology and dry weight of pepper (Capsicum annuum L.) seedlings subjected to continuous watering (CV) or alternate watering (AW) subflotation irrigation. When ABA (10-4 m) was sprayed on to leaves 28, 32, or 37 days after seeding (DAS), leaf growth was limited relative to the controls. Root dry weight, basal root count, and diameter decreased in AW compared with CW-treated seedlings. ABA did not influence root growth of the transplants or subsequent total fruit yield. When ABA was applied to leaves at 20,23, or 29 DAS, there was a transient inhibition of leaf weight increase, but root growth was unaffected. Exogenous ABA may have a practical application as a substitute for drought stress to control transplant growth in the nursery. Chemical name used: abscisic acid (ABA).
Brian A. Kahn* and Daniel I. Leskovar
Single- and double-row arrangements of a fixed population (one plant every 0.285 m2) were compared in factorial combination with two (2002) or five (2003) cultivars for effects on yield and fruit quality of bell pepper (Capsicum annuum L.). Arrangements for 2002 were: (1) 1.9 m between centers of double-row beds, rows on beds 30 cm apart, plants within rows 30 cm apart; (2) single rows 0.95 m apart, plants within rows 30 cm apart; (3) 1.52 m between centers of double-row beds, rows on beds 24 cm apart, plants within rows 37.5 cm apart; and (4) single rows 0.76 m apart, plants within rows 37.5 cm apart. Only arrangements (1) and (2) were used in 2003. Row arrangement did not affect marketable fruit production in Oklahoma in 2002, but single rows resulted in a greater weight of fruit with blossom-end rot than double rows. Arrangement (2) resulted in both a greater weight of U.S. No. 1 fruit and a greater weight of sunburned fruit than arrangement (1) in Texas in 2002. `King Arthur' produced more marketable fruit than `X3R Wizard' in Oklahoma in 2002, but the opposite occurred in Texas. Arrangement (2) resulted in a greater weight of U.S. No. 1 fruit than arrangement (1) in both locations in 2003. Arrangement (2) also resulted in greater weights of sunburned (Oklahoma) or total cull (Texas) fruit than arrangement (1) in 2003. `Lafayette' and `X3R Wizard' produced a greater weight of marketable fruit than `Boynton Bell', `Karma', and `King Arthur' in Texas in 2003, but not in Oklahoma. Plant arrangement × cultivar interactions were not evident in Oklahoma and minimal in Texas. Given the tested population, a single row arrangement is likely to result in higher U.S. No. 1 fruit yields than a double-row arrangement, despite an increased potential for cull fruit production with single rows.
Haejeen Bang*, Daniel I. Leskovar, and Kilsun Yoo
This experiment was conducted to determine the effects of deficit irrigation and growing season on fruit quality, carotenoid content and yield of red-, orange-, and yellow-fleshed diploid and triploid watermelon. Irrigation rates were 1.0 evapotranspiration (ET) and 0.5 ET. Diploid cultivars were Summer Flavor 710 (red), Tendersweet (orange), and Summer Gold (yellow). Triploid cultivars were Summer Sweet 5244 (red), Sunshine (orange), and Amarillo (yellow). Four-week old containerized transplants were planted in the field at TAES-Uvalde on 27 Mar. and 21 May 2003. Deficit irrigation imposed after plants were fully established reduced the individual fruit weight and size in the early planting. Soluble solids content (SSC) and firmness was not affected by irrigation rate in both plantings. SSC varied across cultivars and increased with maturity, particularly for the triploid cultivar Amarillo. In general, triploids were firmer than diploid cultivars. Total carotenoid content was not affected by irrigation during early planting. Diploid and triploid red-fleshed watermelon cultivars had significantly higher carotenoid content than orange- and yellow-fleshed cultivars. The major carotenoid was lycopene (more than 65%), followed by prolycopene (20%) and B-carotene (7%).
Daniel I. Leskovar and Charles S. Vavrina
The effect of cell volume and age of `Texas Grano 1015Y' onion transplants on survival, growth, and yield were evaluated. Transplant ages and cell volume were 5, 7, 9, and 11 weeks (W) and 6.5 cm3 and 20.0 cm3 in Florida; and 6, 8, 10, and 12W, and 4.0 and 7.1 cm3 in Texas. In Florida, total yields were unaffected by transplant age and cell volume, but jumbo size bulbs increased with increasing age from 5 to 9W in 6.5 cm3 cells. Bulb size increased significantly for 11W transplants only in 20.0 cm3 cells. In Texas, survival was reduced for 6W compared to ≥8W transplants. At planting, root count increased linearly with age. Cell volume did not affect root count, plant height, or leaf number, but shoot dry weight was greater in 7.1 cm3 compared to 4.0 cm3. Total jumbo and large size yields were highest for ≥10W in 7. 1 cm3 and ≥8W in 4.0 cm3 cells. Total yields were unaffected by cell size but seedlings in 4.0 cm3 had a 16% decrease of jumbo size compared to 7.1 cm3. The use of 10 and 12W transplants produced in small cell sizes may be viable for onion establishment.
Daniel I. Leskovar and Mark C. Black
Effects of spinach crop management strategies on white rust (Albugo occidentalis), leaf chlorosis, root growth and yield were evaluated in winter 1991/92. Irrigation main plots were low (I-low), medium (I-med) and high (I-high). Fungicide split-plots were none (F0), metalaxyl at planting (F1), and metalaxyl at planting plus experimental CGA 2014 foliar (F2). Genotype split-split-plots were ACX 5044 and ARK 88-354. The Gompertz model best described the white rust disease progress. At all irrigation levels, ACX 5044 had the higher rate of disease increase (rG) and earlier disease onset than ARK 88-354. Metalaxyl delayed disease onset and rG in ACX 5044 only at I-low and I-med, but not at I-high. ARK 88-354 was the least sensitive to fungicides. Yellowness and chlorosis, estimated by spectrophotometric measurements, were higher at I-med and I-high, and with F0, while ARK 88-354 had less chlorosis than ACX 5044. Root diameter was increased with F1 compared to F0. Lateral and tap root fresh and dry weights were higher for ARK 88-354. Yields for ARK 88-354 were significantly higher than ACX 5044. No treatments influenced the number of live or aphids parasitized by Pandora neoaphidis.
Jose Reynaldo A. Santos and Daniel I. Leskovar
Broccoli, cabbage, and cauliflower were grown in the greenhouse on fallowed soil (FS) or on soil previously cropped with broccoli CBS) for three years. Fertilization levels (kg/ha) were none, 67N-22P, and 135N-44P. Inhibition of root and shoot growth components, and leaf color was evaluated at 30, 44, 58, and 72 days after seeding. Shoot and root growth of cauliflower, grown on BS, progressively declined over time, while that of broccoli and cabbage either increased or remained unaffected. Application of fertilizer (67N-22P) improved the shoot growth of cabbage but did not alleviate the symptoms associated with allelopathy, i.e., stunted growth, leaf chlorosis, reduced leaf area, observed in cauliflower. Whole plant extract of broccoli decreased percent germination of cauliflower, and reduced the speed of germination of all three test crops in the order of cauliflower>broccoli>cabbage.
Daniel I. Leskovar and Ronald R. Heineman
Two studies were conducted to determine how greenhouse irrigation systems alter root elongation, root morphology, shoot growth, and water status of `TAM-Mild Jalapeño-1' pepper (Capsicum annuum L.) seedlings. Transplants were grown in containerized trays for 48 days in a greenhouse. Irrigation systems were 1) flotation (FI), 2) 28 days FI plus 14 days overhead (OI; FI + OI), 3) alternate OI and FI (OI–FI), and 4) OI. FI and OI–FI transplants maintained a uniform lateral root length increase between 20 and 41 days after seeding (DAS). In FI + OI and OI transplants, lateral root elongation tended to plateau at ≈31 DAS; however, by increasing the number and length (33%) of basal roots, OI transplants had a total root growth compensation during the remaining growth period. At 41 DAS, OI transplants had a higher shoot: root ratio (S: R = 5) and maintained a higher shoot water potential (Ψstem = –0.58) than FI transplants (S: R = 3; Ψstem= –0.69 MPa, respectively). In the second study, OI transplants maintained higher Ψstem than FI transplants. The latter had a lower stomatal conductance and photosynthesis rate than OI and FI + OI transplants. FI may be used to lower the S: R ratio and promote hardiness in jalapeño transplants.