Luis López-Pérez

Effects of Nitrogen Source on Growth and Development of Strawberry Plants

ABSTRACT An experiment was conducted to study the effects of nitrate (NO3 −) and ammonium (NH4 +) ratios in nutrient solutions on the growth and production of fruits, runners, and daughter plants of strawberry Fragaria x ananassa Duch., grown in a hydroponic system. Five treatments were applied, consisting of different proportions of NH4 + and NO3 − in the nutrient solution. The NH4 +:NO3 − ratios were: T0 = 0:4, T1 = 1:3, T2 = 2:2, T3 = 3:1, and T4 = 4:0, at a constant nitrogen (N) concentration of 4 mol m−3. Growth and morphogenesis were characterized by monitoring leaf-area increase, number of flowers and fruits per plant, and number of daughter plants of first and second generations. Nitrogen and carbon (C) content were measured at the end of the experiment in the organs of both mother and daughter plants. None of the variables related to the growth of the mother plant was affected by the treatments. However, the number of fruits increased with the proportion of NH4 + in the nutrient solution. The number of daughter plants produced was affected only at high NH4 + proportions, and their size (dry matter per daughter plant) and fertility (number of second-generation plants per first-generation plants) were reduced. The N or C content of the plants was not significantly affected by the treatments, but the C/N ratio in the crowns of mother plants was higher in treatments with 25% and 50% NH4 + in the nutrient solution.

Estimating the Nitrogen Concentration of Strawberry Plants from Its Spectral Response

Abstract Estimating the nitrogen (N) status of plants as a function of their spectral response is a promising technique to diagnose and optimize N fertilization. An experiment was conducted in Jiquilpan (Michoacán, México) in which three N levels (0.3, 3, and 20 mM of NO3 − in the irrigation water) were applied to strawberry (Fragaria vesca) in a randomized complete block design with three replicates. The spectral response of strawberry was measured at both the canopy and leaf level using individual wavebands as well as vegetation indices. Individual leaves were separated into three strata (young, mature, and old) and leaf dry matter, leaf area, and N content (% dry matter) were measured in each stratum. Leaf area, biomass, and N content differed significantly between strata. Leaf area, biomass, and N content in all strata were affected by N fertilization. At the canopy level, N content was highly correlated with green reflectance (R550) (r2=0.50) and red reflectance (R680) (r2=0.60) as well as the vegetation indices simple ratio (SR) (r2=0.56), normalized difference vegetation index (NDVI) (r2=0.56), and hyperspectral NDVI (HNDVI) (r2=0.56). For individual leaves, significant differences between strata were found with normalized total pigment to chlorophyll a ratio index (NPCI) and MERIS terrestrial chlorophyll index (MTCI) (p<0.001) as well as R550, photochemical reflectance index (PRI), red edge position (REP), and REP calculated using the MERIS satelite wavelengths (p<0.01). Relationships between spectral indices and N content at the leaf level were found with the youngest leaves only, with NPCI (p<0.01) and MTCI (p<0.05), whereas only R550 responded to N fertilization (p<0.05).

Effectiveness of native arbuscular mycorrhizal consortia on the growth of Agave inaequidens

The aim of this study was to evaluate the effect of eight native consortia of arbuscular mycorrhizal fungi (AMF), a commercial strain and a control without AMF on the growth of Agave inaequidens. Agave seedlings were inoculated and kept under greenhouse conditions for 300 days. At 90, 180 and 270 days after inoculation, the number of leaves and plant height were recorded; at the end of the experiment, fresh and dry weight, head (also known as heart or piña) diameter, leaf area and root length and volume were recorded. The percentage of mycorrhizal colonization, the relative mycorrhizal dependency index and the Dickson index were also calculated. Results showed a growth-promoting effect on agave plants when inoculated with native consortia, namely Barranca de las nueces, El Limón, Agua Dulce and Huizachal, compared to the control. Colonization values were high (45%) and similar to those reported in other studies with agaves. Plants inoculated with the Huichazal consortium obtained the highest Dickson index (9.6). It can be concluded that native consortia are a feasible alternative for use as growth promoters in Agave inaequidens and that they can be a good option as biofertilizer sunder nursery conditions.

Growth dynamics of papaya due to mycorrhizal inoculation and phosphorous fertilization

Papaya is a major fruit export for Mexico; however, the international market is increasingly demanding bio quality, representing a significant production challenge due to the need for bio-ecological and sustainable technologies. Arbuscular mycorrhizal fungi (AMF) can contribute significantly to plant nutrition, particularly in phosphorous (P) uptake. The use of AMF in papaya is yielding encouraging results, but there is a need to define certain aspects regarding agronomic management of AMF-based products. The aim of this study was to evaluate the effect of AMF Glomus sp. Zac-2 and P fertilization on the growth of Cera var. papaya during the nursery stage. For this, a 2 x 3 x 4 tri-factorial experiment (AMF inoculation, P source and P dose) was conducted in a completely randomized design. The variables plant height (PH) and stem diameter (SD) were evaluated every 15 days; dry biomass (DB) and spore density (SD) were assessed at the end of the experiment (90 days). From the DB of plants with and without mycorrhizal inoculation, the relative mycorrhizal dependency index (RMDI) was calculated. Data analysis showed significant differences (P ≤ 0.05) between papaya plants with and without AMF for PH, SD and DB, regardless of the P dose and source. At 75 days, growth increases of more than 500 % were recorded in plants with AMF compared to the non-inoculated plants; the RMDI was 99 %. These results suggest that AMF inoculation in papaya during the nursery phase can benefit further growth in the field. ADDITIONAL

Micorrización de Agave cupreata: Biocontrol de Fusarium oxysporum y promoción del crecimiento vegetal

The effect of mycorrhizal of Agave cupreata in the biocontrol of Fusarium oxysporum and promoting plant growth was evaluated. In greenhouse, seeds of A. cupreata were inoculated with four consortia of arbuscular mycorrhizal fungi (AMF) native: The Huizachal (EH), Agua Dulce (AD), Paso Ancho (PA) and Cerro del Metate (CM), a commercial inoculum mycorrhizal INIFAP® (MI) and a control without AMF. Seven months after inoculating of the AMF, in a group of plants with and without mycorrhizal was evaluated the promoting plant growth and another similar group of plants were inoculated with or without Fusarium oxysporum FPC (Fox) to evaluate the potential biocontrol effect of AMF. The results showed that mycorrhizal plants increased significantly (Tukey, p≤0.05) dry biomass total, in a range between 148 and 239 % more than the control without AMF. At 240 days after inoculation of Fox; the treatments PA+Fox and MI+Fox showed

Nitrate Influx in Rose Plants during Day-Night Cycle

ABSTRACT In herbaceous plants grown in controlled environmental conditions nitrate (NO3−) uptake increases during the day and decreases in the night. The aim of this work was to measure NO3− uptake rates along the day-night cycle, in rose (Rosa hybrida L.) plants grown under controlled environmental conditions. Two independent experiments were conducted inside a growth chamber at 20 ºC and 25 ºC, using rose mini-plants cv. Texas, grown in a hydroponic nutrient film technique (NFT) set-up with at 3.0 mol m−3 NO3− concentration. Dry matter and nitrogen (N) accumulation were registered during growth and NO3− uptake rates were measured during a day-night cycle, using 15N as 15NO3−. In both experiments the hourly estimated N-NO3− accumulation rates are near to the measured uptake rates of 15NO3− and nitrate uptake decrease during the day and increase in the night, in contrast with the herbaceous plants. Results are discussed on the basis of N plant demand and carbohydrates availability.