Genotypic Differences in the Temperature Responses of Tropical Crops: II. SEEDLING EMERGENCE AND LEAF GROWTH OF GROUNDNUT (ARACHIS HYPOGAEA L.) AND PEARL MILLET (PENNISETUM TYPHOIDES S. & H.)

Mohamed, H. A., Clark, J. A. and Ong, C. K. 1988. Genotypicdifferences in the temperature responses of tropical crops.II. Seedling emergence and leaf growth of groundnut (Arachishypogaea L.) and pearl millet (Pennisetum typhoides S. &H.).—J. exp. Bot. 39: 1129-1135. Measurements of seedling emergence and leaf growth of five milletand seven groundnut genotypes were made at soil temperaturesranging from 7 to 27?C. The rate of seedling emergence (R_e)varied greatly between millet genotypes but R_e was remarkablysimilar in groundnut genotypes. In pearl millet there is a strongcorrelation between the rate of germination and the rate ofleaf production, hourly leaf extension and seedling emergence.The results are discussed in terms of the thermal time requirementsof various processes. Key words: Temperature, emergence, groundnut, millet     

Genotypic Differences in the Temperature Responses of Tropical Crops: III. LIGHT INTERCEPTION AND DRY MATTER PRODUCTION OF PEARL MILLET (PENNISETUM TYPHOIDES S. & H.)

Mohamed, H. A., Clark, J. A. and Ong, C. K. 1988. Genotypicdifferences in the temperature responses of tropical crops.III. Light interception and dry matter production of pearl millet(Pennisetum typhoides S. & H.).—J. exp. Bot. 39: 1137–1143. Leaf area development, light interception and dry matter productionof four contrasting pearl millet cultivars were investigatedat mean air temperatures of 19.5, 21, 26 and 31?C. Growth wasslowest as 19.5?C and fastest at 31?C. The canopies of the cultivarsvaried considerably with regard to their light transmissioncoefficients (K₁), from 0.47 for Sanio to 0.23 for Oasis andin their mean efficiency of energy conversion (e), from 1.0to 2.7 g MJ^–1. The ranking of the cultivars in these respectsis consistent with those for germination and early establishmentand early establishment reported in the preceding papers. Key words: Light, dry matter production, millet     

甲基茉莉酸酯对花生种子萌发和贮藏物质降解的影响

甲基茉莉酸酯（Me-Ja）对花生种子萌发基本没有影响,但对下胚轴和根的生长有抑制作用,且与浓度正相关．低浓度Meja促进子叶淀粉酶活性和淀粉降解,高浓度作用相反。Me-Ja部分抑制脂肪降解、贮藏蛋白降解和内肽酶活性,明显抑制脂肪酶活性．文中还讨论了Me-a抑制种子萌发与ABA作用的异同。     

脱落酸和抑制剂对萌发花生子叶肽链内切酶和花生球蛋白降解的影响

脱落酸（Ａｂｓｃｉｓｉｃａｃｉｄ,ＡＢＡ）抑制花生种子萌发的作用与核酸和蛋白质合成抑制剂的作用不同．ＡＢＡ（１００μｍｏｌ／Ｌ）在萌发零时施用,明显抑制肽链内切酶活性和同工酶表现以及花生球蛋白降解,萌发４８ｈ施用ＡＢＡ（１００μｍｏｌ／Ｌ）只降低肽链内切酶活性．ＡＢＡ的抑制作用不依赖于核酸和蛋白质合成．核酸合成抑制剂（３＇－脱氧腺苷,放线菌素Ｄ,５－氟尿嘧啶）和蛋白质合成抑制剂（亚胺环己酮）只能部分降低肽链内切酶活性,对肽链内切酶同工酶表现和花生球蛋白降解无明显影响．实验结果表明花生子叶肽链内酶不是在种子萌发过程中重新（ｄｅｎｏｖｏ）合成,文中讨论了肽链内切酶活性调节和花生贮藏蛋白降解的起始模式．     

PEARL MILLET (PENNISETUM AMERICANUM (L.) LEEKE) AND GRAIN SORGHUM (SORGHUM BICOLOR (L.) MOENCH) ULTRASTRUCTURE

Ultrastructural features of pearl millet (Pennisetum americanum (L.) Leeke) and grain sorghum (Sorghum bicolor (L.) Moench) caryospses were investigated with thin sections of the dry, mature grain in the transmission electron microscope, and fractured kernels in the scanning electron microscope. The pericarp of those grains is comprised of three distinct layers: epicarp, mesocarp of parenchyma cells, and endocarp of compressed cross and tube cells. Mesocarp cells of grain sorghum contain starch granules embedded in a cytoplasmic matrix. The major constituent of sorghum and millet aleurone cells are aleurone grains (protein bodies) and lipid bodies. Subaleurone cells contain a much higher proportion of protein bodies than starch granules, and the protein bodies are structurally distinct from those in the aleurone. The germ scutellar ultrastructures of the two grains were similar; protein bodies, lipid bodies, epidermal cells and parenchyma cells of the germ are described.     

萌发花生种子子叶肽链内切酶的纯化和性质

萌发花生种子子叶的肽链内切酶经硫酸铵沉淀,ＳｅｐｈａｄｅｘＧ－１００凝胶层析,ＤＥＡＥ－纤维素２３阴离子交换层析和ＤＥＡＥ－ＳｅｐｈａｄｅｘＡ５０层析,得到纯化的酶,该酶有两条同工酶,分子量分别为５８和５５ＫＤ,Ｋｍ为９．９μｍｏｌ／Ｌ,是半胱氨型肽链内切酶（ＥＣ３．４．２２）,对未萌发花生种子的贮藏蛋白没有明显降解作用．     

不同活力花生种子子叶内肽酶活性及花生球蛋白的降解

花生种子人工劣变后活力下降,子叶内肽酶活性降低,花生球蛋白降解速率减慢。内肽酶同工酶也发生变化,种子在劣变过程中可能诱导新内肽酶产生。     

TDZ诱导花生幼叶的不定芽和体细胞胚发生的组织学观察

花生实生苗幼叶接种于MS TDZ 0.2mg/L NAA0.4mg/L诱导培养基上经诱导培养,继而转移到无激素培养基MS可获得不定芽和体细胞胚。组织学观察表明,花生不定芽和体细胞胚均起源于愈伤组织表层,不定芽为多细胞起源,而体细胞胚起源于单个胚性原始细胞。体细胞胚的发育经历多细胞原胚、球形胚、心形胚、鱼雷胚和子叶胚等时期发育成小植株。     

GERMINATION AND ATTACHMENT OF ZYGOTES OF HIMANTHALIA ELONGATA (L.) S. F. GRAY1

Germinating zygotes of Himanthalia elongata (L.) S. F. Gray have a prolonged stage free from rhizoids. The spherical zygote flattens when settling on a substratum and a rim-like structure develops at the periphery of the flattened base. Numerous rhizoids appear simultaneously 5–7 days after fertilization. The possible significance of the germling's shape and structure in relation to attachment is discussed.     

The Metabolism of Proline in Higher Plants: II. L-PROLINE DEHYDROGENASE FROM COTYLEDONS OF GERMINATING PEANUT (ARACHIS HYPOGAEA L.) SEEDLINGS

The L-proline-dependent reduction of NAD⁺ has been obtainedwith a soluble enzyme extracted from acetone powders of thecotyledons of 3- to 5-day-old germinating peanut seedlings.The enzyme has been purified approximately 20-fold. NAD⁺ ismuch more effective as an electron acceptor than NADP⁺, thereaction rate with the latter being only 15 per cent that withthe former. The K_m for L-proline at pH 10.3, with NAD⁺ saturating,is 0.30 mM, and that for NAD⁺, with L-proline saturating, is0.25 mM. NADP⁺ is an excellent competitive inhibitor for NAD⁺with a K₁ of 6.2 µM. L-proline, L-proline methyl ester, and 3,4-dehydro-DL-prolineare equally effective as substrates. Thiazolidine-4-carboxylatecatalyses the reduction of NAD⁺ at 63 per cent the rate withL-proline. D-proline is not a substrate nor an inhibitor. L-prolineamide has 11 per cent the activity of L-proline and N-methyl-L-prolinehas a very slight activity. Other proline derivatives or thelower and higher homologues are completely inactive. Incubation with L-proline-¹⁴C in the presence of NAD⁺ yieldsone product which has a higher Rf than proline using butanol-aceticacid-water as the solvent in paper chromatography. Elution ofthis product and treatment with hydrogen peroxide gives severalproducts of high Rf with the same solvent mixture. None of theproducts is -aminobutyrate or glutamic acid. This eliminateseither P2C or P5C as the reaction product.     

Time, Temperature and Germination of Pearl Millet (Pennisetum typhoides S. & H.): III. INHIBITION OF GERMINATION BY SHORT EXPOSURE TO HIGH TEMPERATURE

Seeds of pearl millet were germinated on wet filter paper attemperatures up to 50 ?C. In one experiment, the temperaturewas held at 50 ?C during imbibition and was then lowered to32 ?C or 25 ?C. Germination rate and the maximum fraction ofseeds germinating (G_m) both decreased as the time of exposureto 50 ?C increased. In contrast, exposure to 50 ?C after imbibitionfor 8 h slowed germination but did not significantly reduceG_m. When the ‘high’ temperature imposed after imbibitionwas reduced from 50 ?C to 45 ?C, there was a small reductionin the rate of germination but not in G_m. The responses haveimplications for the optimum time of sowing in the tropics whenmaximum daytime soil temperature at the depth of sowing is inthe range of 45–50 ?C. Key words: Pennisetum typhoides, Temperature, Germination     

Response to Temperature in a Stand of Pearl Millet (Pennisetum typhoides S. & H.): V. DEVELOPMENT AND FATE OF TILLERS

The development of individual tillers in stands of pearl milletwas investigated in a suite of temperature-controlled glasshousesmaintained at mean air temperatures of 19, 22, 25, 28 and 31?C. The rate of leaf appearance of individual tillers was similarto that on the main culm but later tillers produced fewer leaves.Apical dissection revealed that 2–5 leaf primordia failedto emerge from some tillers and the cessation of developmentpreceded any external signs of premature senescence by 3–4weeks. The concept of thermal time is used to determine when leaf appearanceceased on individual tillers. Tiller development stopped synchronouslyat about 430 ?Cd in all treatments, indicating that it was relatedto a common physiological or environmental condition. This periodcorresponded to the start of stem elongation and closure ofcrop canopy but because temperature has a major influence onboth it was impossible to reach a firm conclusion about themechanisms responsible for the cessation of tiller development.The yield and fate of individual tillers are also presented. Key words: Tiller development, Millet, Temperature     

Time, Temperature and Germination of Pearl Millet (Pennisetum typhoides S. & H.): I. CONSTANT TEMPERATURE

The germination of pearl millet (Pennisetum typhoides S. &H.) seeds was investigated at constant temperatures between12 ?C and 47 ?C on a thermal gradient plate. The rate of germination increased linearly with temperaturefrom a base T_b to a sharply defined optimum T_o beyond whichthe rate decreased linearly with temperature, reaching zeroat T_m. The linearity of the response both above and below T_oallowed time and temperature to be combined in a thermal timeat which a specified fraction of the seeds germinated. Withinthe population T_b and T_m were constant.     

Response to Temperature in a Stand of Pearl Millet (Pennisetum typhoides S. & H.): VII. FINAL NUMBER OF SPIKELETS AND GRAINS

An index which incorporates rates of plant growth and of development—athermal interception rate (TIR)/is used to analyse final spikeletand grain number in pearl millet. Growth rate was assumed proportionalto solar radiation intercepted (MJ per plant per day) and developmentalrate to the accumulation of degree days above a previously determinedbase of 10 °C. Measurements were assembled from experimentsin glasshouses with precise temperature control and from a fieldstudy in the tropics. The final number of spikelets was less sensitive to TIR thanthe final number of grains per plant. The critical period forthe determination of grain number is from floral initiationto anthesis (GS2 period). Key words: Temperature, Spikelets, Grains, Pearl millet     

THE ROLE OF MUCILAGE IN THE GERMINATION OF CUIPO,CAVANILLESIA PLATANIFOLIA (H. & B.) H. B. K. (BOMBACACEAE), A TROPICAL TREE

The mucilage in the fruits of cuipo, Cavanillesia platanifolia, is an adaptation to the unpredictable rainfall at the beginning of the rainy season in the tropical moist forests of central Panama. It allows cuipo to germinate rapidly following rains in the early rainy season, before other potential competitors. Mucilage comprises ~27% of the mass of the large (~3.5 g) wind-dispersed fruits of cuipo. Water uptake capacity of cuipo fruits (7 g water/g fruit in 10 min) was greater than that of the diaspores of five wind-dispersed species sympatric with cuipo. Diaspores of these five species lost all their absorbed water within 2 days but cuipo retained it for 2 wk. Experiments using two mucilage treatments (seeds within fruit and seeds alone) and three watering treatments (daily, weekly, and biweekly) indicated that 1) neither mucilage nor watering treatments altered percent germination; 2) the presence of mucilage-rich fruits lessened the effects of drought on seedling development and decreased the degree of wilting; and 3) both treatments interacted in their effects on percent and cause of mortality.     

SEEDS OF KOSTELETZKYA VIRGINICA (MALVACEAE): THEIR STRUCTURE,GERMINATION, AND SALT TOLERANCE. I. SEED STRUCTURE AND GERMINATION

Dormancy of Kosteletzkya virginica (L.) Presl. seeds is primarily due to the impermeability of the seed coat to water. The impermeable structure is assumed to be, in other Malvaceae, the palisade layer of the seed coat. The percentage of seeds capable of imbibition and germination increased with increasing time of storage at low temperatures, but the release from dormancy was not accompanied by decreased seed coat resistance to pressure. Under natural conditions, mechanical damage to the seed coat due to changes in temperature and/or abrasion may render the seeds water permeable. It is not clear what causes water permeability during storage under laboratory conditions. During seed maturation and drying, the inner epidermis of the tegmen partly separates from the rest of the seed coat and an air space, which makes the seed buoyant, is formed around the region of the chalazal cleft. The optimal temperature for germination of K. virginica seeds is between 28 and 30 C in light or darkness.