Abstract
In the present agricultural scenario, the major thrust is to increase crop productivity so as to ensure sustainability. In an earlier study, foliar application of thiourea (TU; a non physiological thiol based ROS scavenger) has been demonstrated to enhance the stress tolerance and yield of different crops under field condition. Towards this endeavor, present work deals with the effect of TU on photosynthetic efficiency and source-to-sink relationship of Indian mustard (Brassica juncea) for understanding its mode of action. The application of TU increased the efficiency of both PSI and PSII photosystems and vegetative growth of plant. The comparative analysis of sucrose to starch ratio and expression level of sugar transporters confirmed the higher source and sink strength in response to TU treatment. The biochemical evidence in support of this was derived from higher activities of sucrose phosphate synthase and fructose-1,6-bis-phosphatase at source; and sucrose synthase and different classes of invertases at both source and sink. This indicated an overall increase in photoassimilate level at sink. An additional contribution through pod photosynthesis was confirmed through the analysis of phosphoenol pyruvate carboxylase enzyme activity and level of organic acids. The increased photoassimilate level was also co-ordinated with acetyl coA carboxylase mediated oil biosynthesis. All these changes were ultimately reflected in the form of 10 and 20% increase in total yield and oil content, respectively under TU treatment as compared to control. Additionally, no change was observed in oil composition of seeds derived from TU treated plants. The study thus signifies the co-ordinated regulation of key steps of photosynthesis and source-to-sink relationship through the external application of TU resulting in increased crop yield and oil content.
Highlights
The continuous increase in global population along with the growing urbanization and impending climate change imposes significant pressure for increasing agricultural crop productivity
The data obtained from two subsequent years confirmed 10% increase in crop yield under TU treatment as compared to control (Table-2)
The present study was undertaken to demonstrate the positive role of TU for enhancing the yield under natural field condition and to understand the underlying mechanism in Indian mustard (Brassica juncea L)
Summary
The continuous increase in global population along with the growing urbanization and impending climate change imposes significant pressure for increasing agricultural crop productivity. There exists a continuous equilibrium between sucrose synthesis and its sequestration inside vacuole and/or transportation towards sink. Any disruption in this equilibrium leads to a higher accumulation of sucrose that mediates feedback inhibition of its synthesis. This ensures the activation of starch biosynthesis process and beyond certain threshold; leaf no longer behaves as source. The higher conversion rate of sucrose into either starch or oil increases the sink strength that supports the accumulation of more photoassimilates required for its growth. Enhanced source and sink strength is a desirable trait that most of the plant biologists wish to achieve so as to enhance plant’s harvest index and crop yield [5,7]
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