Abstract
Lodging is a phenomenon that affects most of the cereal crops including rice, Oryza sativa. This is due to the fragile nature of herbaceous plants whose stems are non-woody, thus affecting its ability to grow upright. Silicon (Si), a beneficial nutrient is often used to toughen and protect plants from biotic and abiotic stresses. Deposition of Si in plant tissues enhances the rigidity and stiffness of the plant as a whole. Silicified cells provide the much needed strength to the culm to resist breaking. Lignin plays important roles in cell wall structural integrity, stem strength, transport, mechanical support, and plant pathogen defense. The aim of this study is to resolve effects of Si on formation of microstructure and regulation of cinnamyl alcohol dehydrogenase (CAD), a key gene responsible for lignin biosynthesis. Besides evaluating silicon, paclobutrazol (PBZ) a plant growth retartdant that reduces internode elongation is also incorporated in this study. Hardness, brittleness and stiffness were improved in presence of silicon thus reducing lodging. Scanning electron micrographs with the aid of energy dispersive x-ray (EDX) was used to map silicon distribution. Presence of trichomes, silica cells, and silica bodies were detected in silicon treated plants. Transcripts of CAD gene was also upregulated in these plants. Besides, phloroglucinol staining showed presence of lignified vascular bundles and sclerenchyma band. In conclusion, silicon treated rice plants showed an increase in lignin content, silicon content, and formation of silicified microstructures.
Highlights
Rice, the main source of carbohydrate for about half the human race is cultivated globally from tropical and temperate Asia, Europe, Africa, North and South America to Australia in a variety of climatic conditions ranging from wettest area to the driest deserts
The lowland rice agriculture is the primary way of cultivation as it is responsible for 86% of the total world rice crop and the SEM-energy dispersive x-ray (EDX) cinnamyl alcohol dehydrogenase (CAD) Lignin Lodging Oryza sativa yields are typically in the range of 2.0–3.5 t ha−1 (Ladha et al, 1997)
The experiment was conducted to evaluate effect of Si and PBZ on yield and growth components with six treatments which are as follows: Control (C) Si applied at 4 g (4) Si applied at 6 g (6) Si applied at 4 g in combination of 400 mg/l PBZ (4T) Si applied at 6 g in combination of 400 mg/l of PBZ (6T) PBZ applied at 400 mg/l only (PBZ) Silicon (SiO2 = 66%) in the form of fine powder and PBZ was applied at 57 days after sowing (DAS) as topdressing on soil surface and foliar spray, respectively
Summary
The main source of carbohydrate for about half the human race is cultivated globally from tropical and temperate Asia, Europe, Africa, North and South America to Australia in a variety of climatic conditions ranging from wettest area to the driest deserts It can be grown in rainfed lowlands, rainfed uplands, mangroves, and even in deepwater areas such as Irrawaddy Delta in Thailand and Mekong in Vietnam and Cambodia. The second type of lodging occurs as a result of excessive bending pressure at the higher internodes, and is determined primarily by the morphology and quality of the culm (Islam et al, 2007). The latter ensues in response to loose and shallow roots with poor anchorage
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