1.
Roles of nitrogen and cytokinin signals in root and shoot communications in maximizing of plant productivity and their agronomic applications.
Gu, J, Li, Z, Mao, Y, Struik, PC, Zhang, H, Liu, L, Wang, Z, Yang, J
Plant science : an international journal of experimental plant biology. 2018;:320-331
Abstract
Nitrogen is an essential, often limiting, factor in plant growth and development. To regulate growth under limited nitrogen supply, plants sense the internal and external nitrogen status, and coordinate various metabolic processes and developmental programs accordingly. This coordination requires the transmission of various signaling molecules that move across the entire plant. Cytokinins, phytohormones derived from adenine and synthesized in various parts of the plant, are considered major local and long-distance messengers. Cytokinin metabolism and signaling are closely associated with nitrogen availability. They are systemically transported via the vasculature from plant roots to shoots, and vice versa, thereby coordinating shoot and root development. Tight linkage exists between the nitrogen signaling network and cytokinins during diverse developmental and physiological processes. However, the cytokinin-nitrogen interactions and the communication systems involved in sensing rhizospheric nitrogen status and in regulating canopy development remain obscure. We review current knowledge on cytokinin biosynthesis, transport and signaling, nitrogen acquisition, metabolism and signaling, and their interactive roles in regulating root-shoot morphological and physiological characteristics. We also discuss the role of spatio-temporal regulation of cytokinins in enhancing beneficial crop traits of yield and nitrogen use efficiency.
2.
Potential of vegetation indices combined with laser-induced fluorescence parameters for monitoring leaf nitrogen content in paddy rice.
Yang, J, Du, L, Gong, W, Shi, S, Sun, J, Chen, B
PloS one. 2018;(1):e0191068
Abstract
Nitrogen (N) is important for the growth of crops. Leaf nitrogen content (LNC) serves as a crucial indicator of the growth status of crops and can help determine the dose of N fertilizer. Laser-induced fluorescence (LIF) technology and the reflectance spectra of crops are widely used to detect the biochemical content of leaves. Many vegetation indices (VIs) and fluorescence parameters have been developed to estimate LNC. However, the comparison among VIs and between fluorescence parameters and VIs has been rarely studied in the estimation of LNC. In this study, the performances of several published empirical VIs and fluorescence parameters for the estimation of paddy rice LNC were analyzed using the support vector machine (SVM) algorithm. Then, the optimal VIs (TVI, MTVI1, MTVI2, and MSAVI) and fluorescence parameters (F735/F460 and F685/F460), which were suitable for LNC monitoring in this study, were chosen. In addition, the combination of the VIs and fluorescence parameters was proposed as the input variables in the SVM model and used to estimate the LNC. Experimental results exhibited the promising potential of the LIF technology combined with reflectance for the accurate estimation of LNC, which provided guidance for monitoring the LNC.