Premise Phosphorus (P) is an essential macronutrient that is often limited in agricultural systems. Determining inorganic phosphate (Pi) contents of plant tissues is crucial for evaluating plant P status. Here, we present a simple, high‐throughput colorimetric microplate technique to measure Pi contents in rice ( Oryza sativa ) leaf tissues, based on the molybdenum blue reaction. Methods and Results We used a hole puncher to sample small equal areas of leaf tissue for Pi extraction. We removed the leaf grinding and weighing steps, which are time‐consuming and normally required to release Pi from the tissues and to measure the biomass for data normalization, respectively. We showed that the punching method yielded comparable results to the conventional grinding method for two rice cultivars grown under various levels of P supply. Conclusions Compared with existing techniques, this protocol is more suited to an initial screening, enabling one researcher to determine the Pi contents of thousands of rice leaf samples within a few hours.

Nitrogen (N) and phosphorus (P) are essential macronutrients required for plant growth and development. Under N and inorganic phosphate (Pi) deficiencies, plants undergo adaptation at physiological, morphological, and transcriptional levels via modulation of endogenous signals, such as phytohormones, in an attempt to increase nutrient acquisition from the environment. Biosynthesis of brassinosteroid (BR), a class of plant hormones, has been shown to be crucial in nutrient deficiency responses in the plant model Arabidopsis. In this study, the responses of rice (Oryza sativa L.) to N and Pi deficiencies were investigated using rice seedlings grown in the presence and absence of a BR biosynthesis inhibitor, propiconazole (PPZ). Transcript levels of BR biosynthesis genes were induced by N and Pi deficiencies. PPZ-treated plants showed retarded growth in both sufficient and deficient conditions. Besides, gene expression of N-and Pi-deficiency-responsive genes was also attenuated by PPZ treatments. These results suggest that inhibition of BR biosynthesis by PPZ could restrain plant growth and adaptation in response to both N and Pi deficiencies.

Phosphorus (P) is an essential mineral nutrient and one of the key factors determining crop productivity. P-deficient plants exhibit visual leaf symptoms, including chlorosis, and alter spectral reflectance properties. In this study, we evaluated leaf inorganic phosphate (Pi) contents, plant growth and reflectance spectra (420–790 nm) of 172 Thai rice landrace varieties grown hydroponically under three different P supplies (overly sufficient, mildly deficient and severely deficient conditions). We reported correlations between Pi contents and reflectance ratios computed from two wavebands in the range of near infrared (720–790 nm) and visible energy (green-yellow and red edge) (r > 0.69) in Pi-deficient leaves. Artificial neural network models were also developed which could classify P deficiency levels with 85.60% accuracy and predict Pi content with R2 of 0.53, as well as highlight important waveband sections. Using 217 reflectance ratio indices to perform genome-wide association study (GWAS) with 113,114 SNPs, we identified 11 loci associated with the spectral reflectance traits, some of which were also associated with the leaf Pi content trait. Hyperspectral measurement offers a promising non-destructive approach to predict plant P status and screen large germplasm for varieties with high P use efficiency.