Horticulturae, Volume 4, Issue 1 (March 2018) – 6 articles

Two greenhouse experiments were conducted to examine the growth and mineral nutrition of four leafy vegetables in a nutrient film technique (NFT) system with water with low to moderate salinity. In Expt. 1, a nutrient solution was prepared using reverse osmosis (RO) water and treatments consisted of supplementing with RO water, tap water, or nutrient solution. In Expt. 2, nutrient solution was prepared using three different water sources (treatments), namely, RO water, tap water, or tap water, plus sodium chloride (NaCl), and supplementing solution was prepared using the same three water sources at one third strength. For both of the experiments, seeds of pac choi ‘Tokyo Bekana’, ‘Mei Qing Choi’, and ‘Rosie’ (Brassica rapa var. chinensis) and leaf lettuce ‘Tropicana’ (Lactuca sativa) were sown and were grown in a growth chamber. Two weeks after sowing, seedlings were transplanted to the NFT systems. Expt. 1 was conducted from 19 April to 19 May 2016 and Expt. 2 from 6 September to 12 October 2016. In Expt. 1, nitrate (NO₃⁻) and phosphorus (P) levels in the tanks decreased, and potassium (K⁺) levels reached almost zero at the end of the experiment when supplemented with RO or tap water. However, calcium (Ca²⁺), magnesium (Mg²⁺), and sulfate (SO₄²⁻) either did not decrease or increased over time. Supplementing water type did not affect the growth of leaf lettuce and ‘Mei Qing Choi’ pac choi; however, fresh weight of ‘Rosie’ pac choi and both fresh and dry weight of ‘Tokyo Bekana’ pac choi were reduced when supplemented with RO water. Leaf sap NO₃⁻ was reduced in ‘Tokyo Bekana’ pac choi, but not in other varieties, when supplemented with RO or tap water. Leaf sap K⁺ decreased in ‘Tokyo Bekana’, but not in other varieties. The supplementing water type did not impact leaf sap Ca²⁺, regardless of vegetable varieties. In Expt. 2, NO₃⁻ in all of the treatments, P in RO water, and K⁺ in RO or tap water decreased in the last week of the experiment. Other macronutrients did not change substantially over time. The addition of NaCl significantly reduced the growth of all the vegetables. ‘Tropicana’ leaf lettuce was the least tolerant to NaCl, followed by ‘Rosie’ pac choi. Water source did not affect leaf Ca²⁺, K⁺, P, SO₄²⁻, and Mg²⁺ except for ‘Tokyo Bekana’ where NaCl addition decreased Ca²⁺ and Mg²⁺. Our results indicated that the tested leafy vegetables differed in response to various types of water used as supplementing or as source water. N, P, and especially K, should be supplemented in the late stage of the experiment, while replacing the whole tank nutrient solution is only necessary when Na⁺ and/Cl⁻ build up to harmful levels. Full article

Paclobutrazol (PBZ) has been associated with effects on the photosynthetic capacity of plants. PBZ affects the growth and development of plants in general. However, little is known about the effects of PBZ on photosynthetic performance and related anatomical features of herbaceous peony (Paeonia lactiflora Pall.) leaves. In the present study, PBZ application resulted in a significant reduction in peony plant height. Furthermore, PBZ application significantly increased photosynthetic rate (Pn), transpiration rate (Tr) and water use efficiency (WUE), but significantly decreased intercellular CO₂ concentration (Ci) at some stages from the bolting stage to the bud stage of the plants, compared to controls. Moreover, PBZ application increased the maximum quantum yield of PSII photochemistry (Fv/Fm), coefficient of photochemical quenching (qP) and intrinsic PSII efficiency (Φ_PSII), but decreased the coefficient of non-photochemical quenching (qN) and non-photochemical quenching (NPQ). Leaves treated with PBZ had a heavy aggregation of chloroplasts close to the cell wall, with distinct grana lamellae, more and bigger starch grains (on average for a chloroplast), and fewer plastoglobuli, as compared to the control. PBZ increased chlorophyll content (SPAD) and the number of chloroplasts in individual cells in the foliar ultrastructure. PBZ-treated leaves had a darker green color with decreased luminosity (L*) and increased hue angle (h°). The results indicated that plants treated with PBZ were superior in terms of increased photosynthetic characteristics when compared with untreated controls. The direct cause of the increase in Pn and leaf greenness of PBZ-treated P. lactiflora may be the increase in chlorophyll content. Full article

Commercial and landrace chile (Capsicum annuum) cultivars are cultivated under furrow irrigation systems in Northern New Mexico. Yield and physiological differences between commercial and landrace chile cultivars under furrow irrigation systems have not been evaluated. In 2011 and 2012 two commercial chiles, ‘Sandia’ and ‘NuMex Big Jim’, with one landrace chile, ‘Chimayo’, were evaluated under four irrigation schedules, with irrigation once every 7, 9, 11, and 13-days. These four schedules represent possible water availability for farmers in Northern New Mexico. In 2011 there were inconsistent yield patterns; fresh red chile yield of ‘Chimayo’ at the seven-day interval was 90% more than at the nine-day interval. ‘Sandia’ had 138% better yields at the seven- than at the nine-day interval. ‘Chimayo’ fresh green chile yields at the nine-day interval were 47% better than the seven-day interval. ‘NuMex Big Jim’ fresh green yields were 40% greater at the seven-day interval than the 13-day interval. In 2012 no yield components were statistically different for cultivars across irrigation intervals. This data shows commercial green and landrace chile cultivars can be furrow irrigated as water becomes available on 7, 9, 11, or 13-day intervals with no yield effect. Full article

A study was conducted in an environmentally controlled greenhouse to evaluate two green bean cultivars, ‘Bronco’ and ‘Paulista’, under three application volumes of irrigation water based on replacing 100, 80, and 60% of evapotranspiration (ET). The experiment was in a split-plot design with three replications, recording vegetative growth, yield, pod parameters, water use efficiency (WUE), and chemical content of pods. The results showed that there were no differences between 80% ET and 100% ET for most parameters. In addition, 80% of ET increased the pod yield and improved the pod parameters and chemical composition. Therefore, this irrigation treatment can increase green bean productivity and improve pod quality. Reducing water application from 100 to 60% of ET progressively increased WUE. The ‘Bronco’ cultivar had a higher plant height, pod yield, WUE, pod weight, pod diameter, and total fiber amount than ‘Paulista’, while the ‘Paulista’ cultivar was superior in total chlorophyll, number of pods per plant, pod length, P, Ca, Mg, Fe, Cu, protein, vitamin C, titratable acid, and soluble sugar. Full article

A greenhouse study was conducted to evaluate the growth and development of poinsettia ‘Prestige Red’ (Euphorbia pulcherrima) grown in a commercial peat-based potting mix (Sunshine Mix #1) amended with biochar at 0%, 20%, 40%, 60%, 80%, or 100% (by volume) at four different fertigation regimes: F1: 100 to 200 mg·L⁻¹ nitrogen (N), F2: 200 to 300 mg·L⁻¹ N (control), F3: 300 to 400 mg·L⁻¹ N, or F4: 400 to 500 mg·L⁻¹ N. The experiment was a two-factor factorial design with 10 replications for each combination of biochar by fertigation. As the percentage of biochar increased, root substrate pore space and bulk density increased, while container capacity decreased. Root rot and red bract necrosis only occurred in F4 combined with 100% biochar. Plants grown in 40% biochar had a similar growth and development to those in 0% biochar. Up to 80% biochar, plants exhibited no significant change, except in terms of dry weight, which decreased at higher biochar percentages (60% and 80%). In summary, at a fertigation rate of 100 mg·L⁻¹ N to 400 mg·L⁻¹ N, up to 80% biochar could be used as an amendment to peat-based root substrate with acceptable growth reduction and no changes in quality. Full article