Rice cultivar evaluation for phosphorus use efficiency

Phosphorus deficiency is one of the most growth-limiting factors in acid soils in various parts of the world. The objective of this study was to screen 25 rice cultivars (Oryza sativa L.) at low, medium, and high levels of soil P. Number of tillers, root length, plant height, root dry weight and shoot dry weight were related to tissue P concentrations, P uptake and P-use efficiency. Shoot weight was found to be the plant parameter most sensitive to P deficiency. Significant cultivar differences in P use efficiency were found. Phosphorus use efficiency was higher in roots than shoots and decreased with increasing levels of soil P. Positive correlations were found among growth parameters such as plant height, tillers, root and shoot weight, and P content of roots and shoots. These results indicate selection of rice cultivars for satisfactory performance under low P availability can be carried out using shoot and root dry weight as criteria.     

Growth and development of maxipak wheat as affected by soil salinity and moisture levels

The effect of soil salinity and soil moisture on the growth and yield of maxipak wheat (Triticum aestivum L.) was studied in a lath-house experiment in whih, chloride-sulphate salt mixtures were used to artificially salinize a sandy loam soil from Al-Jadyriah Baghdad. Five soil salinity levels of ECe's equal to 1.7 (Control) 4.2, 5.8, 8.1, 9.4 and 11.0dSm^–1 were prepared and used at 3 levels of available soil moisture depletion, namely, 25, 50, and 75% as determined by weight. Both growth (vegetative) and yield components were studied throughout the growing season.Results showed that increasing the soil salinity from 1.7 to 11.0 dSm^–1, and decreasing the available soil water from 75 to 25% resulted in independent and significant decreases in Mazipak wheat growth and yield components at different stages of plant development. Root growth showed more sensitivity to both available soil water and soil salinity level than other components. It has been concluded that at soil salinity levels of more than 8.0 dSm^–1, available soil water became a limiting factor on wheat growth and the maintenance of 75% of available soil water during the growth period is recommended to obtain satisfactory grain yield.     

Effect of salinity on phosphate accumulation and injury in soybean

Many soybean [Glycine max (L.) Merr.] genotypes that are grown in solution cultures are highly sensitive to the combination of both salinity and inorganic phosphate (Pi) in the substrate. This effect has been observed on numerous occasions on plants grown in a saline medium that contained a substantial amount of Ca (i.e., CaCl₂/NaCl=0.5 on a molar basis). Because Ca is important in regulating ion transport and membrane permeability, solution culture experiments were designed to examine the effects of various concentrations of Pi and ratios of CaCl₂/NaCl (0 to 0.5 on a molar basis) at a constant osmotic potential (−0.34 MPa) on this adverse interaction. Four soybean cultivars (‘Lee’, ‘Lee 74’ ‘Clark’ and ‘Clark 63’) were tested. No adverse salinity x Pi interaction was found on Lee at any ratio and leaf P and Cl were maintained below 300 and 200 mmol kg⁻¹ dry wt, respectively. Clark, Clark 63 and Lee 74 soybean plants, on the other hand, were severely injured by solution salinity (−0.34 MPa osmotic potential) when substrate Pi was ≥0.12 mM. Reduced substrate Ca did not intensify the salinity x Pi interaction. On the contrary, the onset of injury was hastened and more severe with increased CaCl₂/NaCl ratios in isotonic solutions. Shoot and root growth rates decreased as injury increased. Leaf P concentrations from these cultivars grown in saline solutions with 0.12 mM Pi were excessive (>600 mmol kg⁻¹ dry wt) compared with concentrations commonly found in soybean leaf tissue yet they were independent of the severity of injury. Since leaf Cl increased wiht increased CaCl₂/NaCl ratio, we suspect that the severity of foliar injury was related to the combined effects of excessive P and Cl within the tissue. Lee 74, the only injured cultivar examined that excluded Cl from its leaves, was less sensitive than either Clark cultivar and its injury was characteristically different. Other ion interactions were reported that may have played a role in injury susceptibility.     

Transformations and fate of sheep urine-N applied to an upland U.K. pasture at different times during the growing season

The fate of sheep urine-N applied to an upland grass sward at four dates representing widely differing environmental conditions, was followed in soil (0–20 cm) and in herbage. Urine was poured onto 1-m² plots to simulate a single urination in August 1984 (warm and dry), May (cool), July and August 1985 (cool and wet) at rates equivalent to 40–52 g N m⁻². The transformation of urine-N (61–69% urea-N) in soil over a 6–7 week period followed the same general pattern when applied at different times during the season; rapid hydrolysis of urea, the appearance of large amounts of urine-N as ammonium in soil extracts, and the appearance of nitrate about 14 days after application. The magnitude of “apparent” nitrification however differed markedly with environmental conditions, being greatest in May 1985 when a maximum of 76% of the inorganic soil N was in the form of nitrate. At all other application dates nitrate levels were relatively low. With the August 1984 application soil inorganic N returned to control levels (given water only) after 31 days but considerable amounts remained in soil for 60–90 days with the other applications. Weekly cuts to 3-cm indicated that increases in herbage dry matter and N yields in response to urine application were greatest in absolute terms after the May 1985 application and continued for at least 70 days with all applications. Relative to control plots the May application resulted in a 3-fold increase in herbage DM compared with corresponding values of 6-, 5-, and 7-fold increases with the August 1984, July and August 1985 applications. Recovery of urine-N in herbage was poor averaging only 17% of that applied at different dates, while recovery in soil extracts was incomplete. The exact routes of loss (volatilisation, leaching, denitrification or immobilisation) were not quantified but it is evident that substantial amounts of urine-N can be lost from the soil-plant system under upland conditions.     

Effects of environmentally hazardous chemicals on the emergence and early growth of selected Australian plants

The effect of soil-incorporated copper, tri-allate, and anthracene on the emergence and early growth of three Australian native species (Banksia ericifolia, Casuarina distyla andEucalyptus eximia) and three crop species (Avena sativa, Cucumis sativus andGlycine max), was assessed using OECD Test Guideline 208. The crop species are sensitive species used in overseas phytotoxicity testing, and their responses were compared with those of the native species. Seeds were grown in pots in a glasshouse in a sandy loam soil at the chemical concentrations of 0, 10, 100, 1000 and 2000 mg kg^–1. LC50 and EC50 values were determined for each species. The most sensitive species was the monocotyledonA. sativa, while among the five dicotyledonsC. distyla was most sensitive. All three chemicals delayed emergence and affected seedling growth. The results indicate that the conditions of the OECD Test Guideline can be met under Australian conditions, but that the Guideline requires modification for use with Australian native species.     

Modifications to the photosynthetic apparatus of higher plants in response to changes in the light environment

A brief review of the photosynthetic apparatus of higher plants is given, followed by a consideration of the modifications induced in this apparatus by changes in light intensity and light quality. Possible strategies by which plants may optimize photosynthetic activity by both long- and short-term modifications of their photosynthetic apparatus in response to changing light regimes are discussed.     

Glycine decarboxylase is confined to the bundle-sheath cells of leaves of C3−C4 intermediate species

Immunogold labelling has been used to determine the cellular distribution of glycine decarboxylase in leaves of C₃, C₃–C₄ intermediate and C₄ species in the genera Moricandia, Panicum, Flaveria and Mollugo. In the C₃ species Moricandia foleyi and Panicum laxum, glycine decarboxylase was present in the mitochondria of both mesophyll and bundle-sheath cells. However, in all the C₃–C₄ intermediate (M. arvensis var. garamatum, M. nitens, M. sinaica, M. spinosa, M. suffruticosa, P. milioides, Flaveria floridana, F. linearis, Mollugo verticillata) and C₄ (P. prionitis, F. trinervia) species studied glycine decarboxylase was present in the mitochondria of only the bundle-sheath cells. The bundle-sheath cells of all the C₃–C₄ intermediate species have on their centripetal faces numerous mitochondria which are larger in profile area than those in mesophyll cells and are in close association with chloroplasts and peroxisomes. Confinement of glycine decarboxylase to the bundle-sheath cells is likely to improve the potential for recapture of photorespired CO₂ via the Calvin cycle and could account for the low rate of photorespiration in all C₃–C₄ intermediate species.Abbreviation and symbol kDa kilodaltons - CO₂ compensation point     

Behavior of chloroplasts and chloroplast nuclei during spermatogenesis in the fern,Pteris vittata L.

Summary The fate of the chloroplasts and chloroplast nuclei (cp-nuclei) was followed during spermatogenesis in the fernPteris vittata L. by epifluorescence microscopy after staining with 4-6-diamidino-2-phenylindole (DAPI) and by quantitation of chloroplast DNA (cp-DNA) by fluorimetry using a video intensified microscope photon counting system (VIMPICS). The spores were grown on solid medium that contained antheridiogen (An_ptd), and formed an antheridium initial on the protonema cell. The antheridium initial divided and produced 16 spermatocytes and 3 surrounding cells. The chloroplasts in the spermatocytes decreased in volume as cell division was repeated, until finally the volume of each chloroplast was 1/15 of that of the primary chloroplasts. The DNA content of the chloroplasts was also reduced to 1/5 of the original value and when the sperm matured, the fluorescence of cp-DNA disappeared. In the 16-cell spermatocyte, the recognition of the fluorescence of chlorophyll in the chloroplasts with a green excitation filter became difficult. But, the plastids could be observed until the final stage of the sperm. From these observations, it appears that there are two steps in the metamorphosis of chloroplasts during spermatogenesis in the fern. The first step involves the decrease in the volume of chloroplasts, accompanied by reduction of the DNA content, and the second step involves the change of the physical state of chloroplasts to amyloplasts and the disappearance of the cp-DNA from the amyloplasts.     

水稻原生质体产生细胞团的冰冻保存和冻后再生植株形成

水稻(Oryza sativa L.)原生质体产生的细胞团加上10-20％的二甲亚枫(DMSO)和10-20％的蔗糖,置于液氮中保存。冻后细胞生存率达到对照的40-50％。存活的细胞在附加2×10~(-5)mol/l 2,4-D 的Linsmier-Skoog(Ls)固体培养基上再生长,然后将形成的愈伤组织块转到附加10~(-6)mol/l NAA,4×10~(-6)mol/l 激动素和10~(-6)mol/l 2 IP 及8％的蔗糖的 LS培养基上分化出芽并形成植株。     

甜椒花药绒毡层的二型性及其组织化学研究

在甜椒（Capsicum annuum L.)中,靠近花粉中部的绒毡层自药隔产生,由较大的细胞组成,而花药外部区域的其余的绒毡层细胞较小,来自于初生壁层,前者的细胞具有大液泡和较大的细胞核,甲基绿－派罗宁和汞－溴酚蓝染色反应较后者弱,在造孢组织时期,二者液泡内都含有较大的球形的酸性磷酸酶颗粒,在以后的发育中,这种颗粒消失,在减数分裂时期,两种绒毡层的DNA,RNA和蛋白质合成活动增强,来自药隔的绒毡层积累了更多的DNA,绒毡层在解体时酸性磷本酶活性很高,两种不同的绒毡层退化过程相似,在全部发育过程中绒毡层内无淀粉粒。