Abstract
Maintaining carbohydrate biosynthesis and C assimilation is critical under phosphorus (P) deficiency as inorganic P (Pi) is essential for ATP synthesis. Low available P in agricultural soils occurs worldwide and fertilizer P sources are being depleted. Thus, identifying biosynthetic traits that are favorable for P use efficiency (PUE) in crops is crucial. This study characterized agronomic traits, gas exchange, and chlorophyll traits of two wheat genotypes that differ in PUE. RAC875 was a P efficient genotype and Wyalkatchem was a P inefficient genotype. The plants were grown in pots under growth room conditions at two P levels; 10 mg P kg–1 soil (low P) and 30 mg P kg–1 soil (adequate P) and gas exchange and chlorophyll fluorescence were measured at the vegetative and booting stages using a portable photosynthesis system (LI-6800, LI-COR, United States). Results showed significant differences in some agronomic traits between the two wheat genotypes, i.e., greater leaf size and area, and a higher ratio of productive tillers to total tillers in RC875 when compared with Wyalkatchem. The CO2 response curve showed Wyalkatchem was more severely affected by low P than RAC875 at the booting stage. The relative ratio of the photosynthetic rate at low P to adequate P was also higher in RAC875 at the booting stage. Photochemical quenching (qP) in RAC875 was significantly higher when compared with Wyalkatchem at the booting stage. Maintaining CO2 fixation capacity under low P and higher qP would be associated with P efficiency in RAC875 and measuring qP could be a potential method to screen for P efficient wheat.
Highlights
Phosphorus (P) is an essential macronutrient for higher plants and an important fertilizer for crops, but P fertilizer sources are being depleted (Vance et al, 2003)
This study found that a P efficient wheat genotype (RAC875) had agronomic traits that may explain its ability to
This study showed a significant reduction in photosynthetic rate in both wheat genotypes under low P (Tables 4, 5 and Figures 4A,B)
Summary
Phosphorus (P) is an essential macronutrient for higher plants and an important fertilizer for crops, but P fertilizer sources are being depleted (Vance et al, 2003). The absorbed light has three potential fates: (1) it is used to drive photosynthesis, (2) released as heat, and (3) reemitted as fluorescence (Maxwell and Johnson, 2000) These are competition processes and how they compete with one another will affect the crop yield and biomass. The quantum efficiency of photosystem II (PSII; PSII), photochemical quenching (qP), and electron transport rate (ETR) are indicators for the efficiency of photosynthesis, while non-photochemical quenching (NPQ) is an indicator of dissipated heat (Murchie and Lawson, 2013) Gas exchange such as photosynthetic rate can be used to evaluate the photosynthetic potential of plants (Johnson and Murchie, 2011). A similar result in wheat grown under well-watered conditions was reported by Wasaya et al (2021)
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