Yoshida - 1981 - Fundamentals of Rice Crop Science

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NUTRITIONAL DISORDERS 181 Iron. Entire leaves become chlorotic and then whitish. If the iron supply is cut suddenly, newly emerging leaves become chlorotic. Manganese. Plants are stunted but have a normal number of tillers. Interveinal chlorotic streaks spread downward from the tip to the base of the leaves, which later become dark brown and necrotic. The newly emerging leaves become short, narrow, and light green. Zinc. The midribs of the younger leaves, especially at the base, become chlorotic. Brown blotches and streaks appear on the lower leaves, followed by stunted growth. Tillering may continue. The size of the leaf blade is reduced, but that of the leaf sheath is little affected. In the field, uneven growth and delayed maturity are characteristics of zinc deficiency. Boron. Plant height is reduced. The tips of emerging leaves become white and rolled as in the case of calcium deficiency. The growing point may die in a severe case, but new tillers continue to be produced. Copper. The leaves appear bluish green, and then become chlorotic near the tips. The chlorosis develops downward along both sides of the midrib; it is followed by dark-brown necrosis of the tips. The new, emerging leaves fail to unroll and appear needle-like for the entire leaf or, occasionally, for half the leaf, with the basal end developing normally. Low silicon content. Leaves become soft and droopy. d. Toxicity symptoms Iron. Tiny brown spots appear on the lower leaves, starting from the tips and spreading toward the bases. These spots combine on interveins. Leaves usually remain green. In a severe case, the entire leaf looks purplish brown. Manganese. The plant is stunted and tillering is often limited. Brown spots develop on the veins of the leaf blade and leaf sheath, especially on lower leaves. Boron. Chlorosis occurs at the tips of the older leaves, especially along the margins. Large, dark-brown elliptical spots then appear. The leaves ultimately turn brown and dry up. Aluminum. The interveinal chlorosis is orangish yellow. In severe cases, the chlorotic portions may become necrotic. High salt injury. Growth is stunted and tillering reduced. Leaf tips become whitish and, frequently, some parts of the leaves become chlorotic. Iodine. Small brown spots appear on the tips of lower leaves. These spots spread over the entire leaf, resulting in yellowish-brown or brown discoloration. The affected leaves eventually die. 4.3.2. Plant tissue analysis The term plant tissue analysis usually refers to the inorganic analysis of plant tissues. However, analysis for some organic constituents and assay for enzyme activity have been proposed for the diagnosis of the nutrient status in plant tissues. The iodine test for starch in rice leaf sheaths and a simplified paper chromatography for asparagine in leaf blades are effective in determining a crop’s need for nitrogen topdressing at panicle initiation (Kiuchi 1968, Ozaki 1955). An assay for
182 FUNDAMENTALS OF RICE CROP SCIENCE ribonuclease is useful for diagnosing zinc deficiency in orchard trees (Kessler 1961). a. Units and expressions used for analytical results. In inorganic analysis, two units are commonly used on a dry weight basis: Thus, Percentage (%): grams nutrient per 100 gram plant material Parts per million (ppm): milligrams nutrient per kilogram plant material 1% = 10 4 ppm The expression of chemical form for analytical results varies among reports. In the old literature, analytical results are normally given in the form of oxides such as P 2 O 5 and K 2 O. In recent years, the trend is to use the elemental forms such as P and K. Under most conditions, convenience dictates which form to use. In greenhouse and laboratory studies, the elemental forms are preferred because they are simpler. Some scientists use milligram atom or microgram atom percent. These expressions may be useful in basic studies where, for example, the element content is related to an enzyme activity. However, they should be avoided in plant tissue analysis for diagnostic purposes and related greenhouse studies. b. Sampling procedure. In sampling plant materials, problems are often encountered in determining which plant parts to sample, when to sample, and how to replicate the sampling. The whole shoot, the leaf blades, or the Y -leaf (the most recently matured leaf blade) are normally used for tissue analysis in rice (Yoshida et al 1976). In most cases, deficiency or toxicity symptoms appear when plants are young and small; hence, the whole plants (excluding roots) may be sampled for chemical analysis. The grain is generally not suitable for diagnosis because its chemical composition is least affected by the nutrient supply. The rice leaf sheath functions as a storage organ for potassium, and the potassium content of the leaf blade tends to be maintained at the expense of the leaf sheath. When the plant becomes deficient in potassium, a larger decrease occurs in Table 4.2. Potassium content in different parts of the rice plant at panicle initiation. a K content (%) in Plant Position Normal K-deficient part plants plants Leaf blade Upper 2.90 1.51 Lower 2.88 1.21 Leaf sheath Upper 3.36 0.90 Lower 3.68 0.52 a Matsuzaka et al (1962).
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FOREWORD Rice is vital to more than
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CONTENTS Foreword Preface GROWTH AN
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3.2. Adaptation to Submerged Soils
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4.5. Corrective Measures for Nutrit
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1 .1. OUTLINE OF THE LIFE HISTORY T
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GROWTH AND DEVELOPMENT OF THE RICE
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Table 7.6. An example of high yield
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REFERENCES AGRICULTURAL POLICY STUD
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Yoshida - 1981 - Fundamentals of Rice Crop Science

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