Early Nitrogen Deficit Stress Detection in Maize (<i>Zea mays</i>) Seedlings Using Chlorophyll Fluorescence Technology

Detecting N-deficiency early in a plant’s development before visual symptoms become pronounced and irreparable damage is done is crucial to maintaining optimum grain yield and biomass production. Chlorophyll fluorescence technology (CFT) is a quick, non-invasive, non-destructive, and informative technique that is used to study the physiological status of plants at any given stage of development. The objective of the study was to determine the photosynthetic and growth responses of N-deficient maize seedlings. Two N treatments, 10 t/ha N and 50 t/ha N, were evaluated in a greenhouse in a completely randomized design with 12 replications. The results showed a significantly (p 2 assimilation rate, maximum quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, and chlorophyll concentration in plants that received 50 t/ha N compared to plants on 10 t/ha N at 3 and 4 weeks after fertilizer application (WAFA). In contrast, plants on 10 t/ha showed a higher level of non-photochemical stress due to up-regulation of nitric oxide production in PSII [Y(NO)] than plants on 50 t/ha. Non-photochemical quenching due to down-regulation of nitric oxide production in PSII [Y(NPQ)] was comparable (p > 0.05) in both treatments. There was no significant difference in plant height, although wider stem girth was recorded in plants on 50 t/ha. The significantly higher levels of Y(NO) in plants on 10 t/ha N suggest an alteration in nitrogen metabolism and increased production of reactive nitrogen species which may potentially cause cellular damage if not diagnosed early and managed adequately

Effect of organic photovoltaic and red-foil transmittance on yield, growth and photosynthesis of two spinach genoty

The galloping rise in global population in recent years and the accompanying increase in food and energy demands has created land use crisis between food and energy production, and eventual loss of agricultural lands to the more lucrative photovoltaics (PV) energy production. This experiment was carried out to investigate the effect of organic photovoltaics (OPV) and red-foil (RF) transmittance on growth, yield, photosynthesis and SPAD value of spinach under greenhouse and field conditions. Three OPV levels (P0: control; P1: transmittance peak of 0.11 in blue light (BL) and 0.64 in red light (RL); P2: transmittance peak of 0.09 in BL and 0.11 in RL) and two spinach genotypes (bufflehead, eland) were combined in a 3 × 2 factorial arrangement in a completely randomized design with 4 replications in the greenhouse, while two RF levels (RF0: control; RF1: transmittance peak of 0.01 in BL and 0.89 in RL) and two spinach genotypes were combined in a 2 × 2 factorial in randomized complete block design with four replications in the field. Data were collected on growth, yield, photosynthesis and chlorophyll content. Analysis of variance (ANOVA) showed significant reduction in shoot weight and total biomass of spinach grown under very low light intensities as a function of the transmittance properties of the OPV cell used (P2). P1 competed comparably (p > 0.05) with control in most growth and yield traits measured. In addition, shoot to root distribution was higher in P1 than control. RF reduced shoot and total biomass production of spinach in the field due to its inability to transmit other spectra of light. OPV-RF transmittance did not affect plant height (PH), leaf number (LN), and SPAD value but leaf area (LA) was highest in P2. Photochemical energy conversion was higher in P1, P2 and RF1 in contrast to control due to lower levels of non-photochemical energy losses through the Y(NO) and Y(NPQ) pathways. Photo-irradiance curves showed that plants grown under reduced light (P2) did not efficiently manage excess light when exposed to high light intensities. Bufflehead genotype showed superior growth and yield traits than eland across OPV and RF levels. It is therefore recommended that OPV cells with transmittance properties greater than or equal to 11% in BL and 64% in RL be used in APV systems for improved photochemical and land use efficiency