Effects of abscisic acid and its related compounds on rice seedling growth

Rice seedlings with the mesocotyl and coleoptile (the undeveloped leaves enclosed in the coleoptile) are here referred to as MC type seedlings and are considered to be suitable for deep sowing. We investigated the effects of abscisic acid (ABA) and several of its related compounds on the occurrence of MC type seedlings and on rice mesocotyl growth. Rice (Oryza sativa L. cv. JC 91) seedlings were grown on 0.8% agar medium in the presence or absence of various kinds of ABAs under aseptic conditions at 30 °C in the dark for 14 days. The activity of the R isomer of ABA (R-ABA) was slightly less than that of the naturally occurring S form (S-ABA) concerning the occurrence of MC type rice seedlings and the growth of the rice mesocotyl. In addition, the racemate of R-and S-ABA (RS-ABA) is less effective than R-ABA and S-ABA alone.Trans-ABA had no activity in relation to both percent occurrence of MC type seedlings and mesocotyl growth. The results of the present study suggest that the occurrence of MC type rice seedlings and the growth of rice mesocotyls were closely related to structure-activity relationships with analogs of ABA.     

Effect of NaCl and PEG 6000 on germination and seedling growth of rice (ryza sativa L.)

Germination and seedling growth of rice was studied in NaCl and PEG 6000 solutions having osmotic potentials −0.2, −0.4, −0.6 and −0.8 MPa. At isoosmotic concentrations, the NaCl proved more harmful to germination, seedling growth, per cent moisture content of seedling organs as well as mobilization of food matter from seed to the growing seedlings. This fact suggested that in rice, at least in the early stage, a specific ion effect rather than osmotic effect is the prime cause of salt injury. Compared to susceptible cultivar, the tolerant one was less inhibited by salinity.     

Effect of seedling treatment on growth and yield of sugar beet in the field

Sugar-beet seeds were germinated (1) in a growth cabinet at 20°C lit continuously by fluorescent tubes (L), (2) in a cabinet at 20°C lit by fluorescent tubes for 16 h/day (S), (3) in a cage with glass roof and open sides with natural illumination (N), or (4) in the open ground (D). The seedlings from the cabinets and cage were transplanted to the field when they had two true leaves. Samples were taken on six occasions during growth, and leaf areas and dry weights determined. There were no differences between treatments in total number of leaves produced or leaf area duration. Leaf area per plant increased fastest on L plants at first, but from mid-June until end of July drilled plants had the largest leaf surface. From August onwards S plants had the largest area. Although treatment had little effect on growth of the tops, roots grew fastest throughout the season on the plants raised in growth cabinets and the final mean root dry weight of L and S plants was 39% greater than of N and D plants. Throughout the season L and S plants had a larger root:top ratio than plants raised in the cage or drilled directly in the field. The larger roots of plants raised in the cabinets evidently provided a larger sink for carbohydrate and increased the mean photosynthetic efficiency of the leaves over the whole season by 11 % and increased yield of roots by 6 tons/acre.     

钾镉双重处理对籽粒苋幼苗生长及元素积累的影响

采用水培法对不同浓度K-Cd双重处理条件下籽粒苋(Amaranthus hypochondriacus Linn.)幼苗根、茎和叶干质量以及根和地上部分Cd、K、P、Ca、Zn、Fe、Mn和Cu含量的变化进行了分析.结果表明:在Cd浓度相同的条件下,随K浓度的提高(0.0、2.5和20.0 mmol·L-1),籽粒苋根、茎和叶的干质量均呈逐渐增加的趋势;各部位的Cd含量均呈现逐渐下降的趋势;根和地上部分的K和Zn含量增加、Ca含量无明显变化、Fe含量呈持续降低的趋势;根中Mn含量无明显变化规律、Cu含量逐渐降低,而地上部分Mn含量总体上增加、Cu含量则无明显的变化规律.在K浓度相同的条件下,随Cd浓度的提高(0、5、25和45 μmol·L-1),籽粒苋幼苗茎和叶的干质量逐渐降低、根的干质量在较高浓度Cd处理条件下也均降低;不同部位Cd含量均不断增加;根和地上部分的Ca、K、Zn和Mn含量基本呈逐渐降低的趋势、Fe含量呈先增加后降低的趋势;根中P和Cu含量大体呈持续降低的趋势、地上部分P和Cu含量则呈先增加后降低的趋势.在不同浓度K-Cd双重处理条件下籽粒苋的根冠比差异不显著,其中5μmol·L-1Cd处理组幼苗的根冠比均最大.总体上看,在K-Cd双重处理条件下籽粒苋幼苗根、茎和叶中Cd含量的增幅均小于Cd单一处理,Cd的迁移系数也有所降低.研究结果显示:较高浓度的Cd处理对籽粒苋幼苗的生长及体内营养元素积累均有一定的抑制作用,而添加K能够减弱籽粒苋对Cd的积累和迁移能力、减轻Cd胁迫的伤害程度.据此,建议在用籽粒苋进行Cd污染环境修复时施用适量的K肥.     

Effect of gibberellins on growth of pea seedling internode

Elongation of internode segments of dwarf pea seedlings excised 4 mm below the plumular hook was stimulated by GA₃ but not by GA₁ or GA₅. However, all three gibberellins induced cell elongation in the region from which this segment was isolated on application to intact seedlings. It is concluded that GA₁ and GA₅ are converted to a GA₃-like hormone. Measurement of epidermal cell elongation in the epicotyl further indicates that GA₃ or a GA₃-like hormone may be the functional form of the hormone required for cell elongation.     

Effect of organic amendments on seedling infection of rice caused byRhizoctonia solani

Summary Soils amended with organic amendments such as rice chaff, mustard cake, neem cake, saw dust and farm yard manure significantly reduced the seedling infection of rice owing toRhizoctonia solani. Significant increase in shoot growth was noticed in soils amended with organic amendments while reduction in root growth of rice seedlings was also observed owing to the addition of organic amendments such as sunflower cake, mustard cake, coconut cake and farmyard manure.     

Effect of temperature on seedling growth under impeding conditions

Studies were carried out under controlled laboratory conditions to evaluate the seedling growth capacities of chickpea (Cicer arietinum L.) varieties Pusa 209 and H208 at constant temperatures of 15, 20, 25 and 28°C (±0.5°C) and of pigeonpea (Cajanus cajan L.) variety Prabhat at 20 and 28°C (±0.5°C). Seedling growth at any given time was found to depend on ‘a’, the growth at no impedance, and ‘b’, the impedance growth factori.e., decrease in growth with increase in impedance, and on temperature. The optimum temperature for chickpea was found to be in the range of 20 to 24°C for better seedling growth characteristics, whereas for pigeonpea, 28°C was found to be more congenial than 20°C. Chickpea varieties differed in their response to temperature. Part of the M. Sc. thesis of first author submitted to the Indian Agricultural Research Institute, New Delhi-110012, India.     

Amelioration of lead and mercury effects on germination and rice seedling growth by antioxidants

Germination of two rice (Oryza sativa L.) cultivars (Ratna and IR 36) in the presence of 10 μM PbCl2 and 10 μM HgCl2 decreased germination percentage, germination index, shoot/root length, tolerance index and dry mass of shoots and roots. Mercury was more toxic than lead. Reduced glutathione (GSH), cysteine (Cys), ascorbic acid, and α-tocopherol alleviated the adverse effects of these metals on plants in the order GSH > Cys > ascorbic acid > α-tocopherol. The effects were more pronounced in tolerant cultivar IR 36 than in the relatively susceptible cultivar Ratna. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of temperature associated with levels of bulk density on rice seedling emergence

Summary A laboratory study was conducted to find out the effect of temperatures on rice seedling emergence under different levels of bulk density. The temperatures ranging from 10 to 40°C in increments of 5°C were maintained constant with ±1°C accuracy. The bulk density levels were 1.3, 1.5, 1.7, and 1.9 g cm⁻³. Aluminum cylinders with top open and bottom provided with a removable 20-mesh brass screen, were used as soil containers. The moisture content in soil was always above field capacity which could be accomplished by placing the cylinders in a tray in which water level was maintained constant to 5 cm depth. Seedling emergence counts were taken till the 10th day of seeding. At the end of the experiment, observations on root and shoot elongations were recorded. Emergence was maximum at 25 and 30°C under 1.3 and 1.5 g cm⁻³, and decreased at 35, 20, and 15°C. As compared to the lower bulk densities, the reduction in emergence under 1.7 g cm⁻³ was smaller at 25 and 30°C than at 35°C. This was ascribed to greater seedling vigour at 25 and 30°C, as could be inferred from larger root and shoot elongation. The reduction in emergence at lower temperatures (20 and 15°C) might be due to delay in time of germination as well as less seedling vigour. The soil under 1.9 g cm⁻³ was sufficiently dense that the seedlings could not emerge except a few ones at 25 and 30°C.     

Glutathione reduces the inhibition of rice seedling root growth caused by cadmium

We investigated the effects of agents known to affect cellular glutathione (reduced form, GSH) levels on the growth of rice seedlings treated with Cd. CdCl₂ was more effective than CdSO₄ in inhibiting root growth. However, CdCl₂ had no effect on shoot growth. GSH, a substrate for phytochelatin synthesis, was effective in counteracting growth inhibition of roots by CdCl₂. Root growth in the CdCl₂ medium was found also to be enhanced by the addition of L-glutamic acid and L-cysteine, both of which are substrates for GSH formation. Buthionine sulfoximine, an inhibitor of GSH synthesis, rendered the roots susceptible to growth inhibition by Cd. Our results suggest that GSH level may play a role in regulating Cd-inhibited growth of rice roots.Abbreviations BSO buthionine sulfoximine - GSH reduced form glutathione     

Effect of brassinosteroids on salinity stress induced inhibition of seed germination and seedling growth of rice (Oryza sativa L.)

The effect of 24-epibrassinolide and 28-homobrassinolide on the inhibitionof germination and seedling growth of rice (Oryza sativa) induced bysalinity stress was studied. Brassinosteroids were found to reverse theinhibitory effect on germination and seedling growth. The activation ofseedling growth by brassinosteroids under salinity stress was associatedwith enhanced levels of nucleic acids and soluble proteins.     

Effect of light on seed germination and seedling growth ofMerremia species

The seeds ofMerremia aegyptia are indifferent to light conditions for germination, which becomes 100% in the first 24 hrs. On the contrary, inM. dissecta the highest percentage was found in red light within the first 24 hrs. This difference was lost later on except in far-red. The seedling growth of the two species was least in blue and red lights, respectively. However, the growth of hypocotyl in the former species was faster than the latter.     

镧浸种对水稻种子萌发及幼苗生长的影响

以水稻种子为材料,研究了稀土元素镧对水稻种子活力和幼苗生长的影响。结果表明,1~20mg.L-1La3+处理能提高水稻种子的活力,提高蛋白酶、淀粉酶和脂肪酶的活性,并能促进水稻茎、叶和根系的生长,其中10mg.L-1La3+处理效果最佳。当浓度超过30mg.L-1时,水稻种子萌发和幼苗生长受到抑制。此外,镧对水稻植株地下部分(根系)生长的影响比地上部分(茎叶)生长的影响要明显。镧对水稻种子萌发期间3种酶活性的影响程度表现为蛋白酶>脂肪酶>淀粉酶。     

Evaluation of bacteria isolated from rice for plant growth promotion and biological control of seedling disease of rice.

Of 102 rhizoplane and endophytic bacteria isolated from rice roots and stems in California, 37% significantly (P < or = 0.05) inhibited the growth in vitro of two pathogens, Achlya klebsiana and Pythium spinosum, causing seedling disease of rice. Four endophytic strains were highly effective against seedling disease in growth pouch assays, and these were identified as Pseudomonas fluorescens (S3), Pseudomonas tolaasii (S20), Pseudomonas veronii (S21), and Sphingomonas trueperi (S12) by sequencing of amplified 16S rRNA genes. Strains S12, S20, and S21 contained the nitrogen fixation gene, nifD, but only S12 was able to reduce acetylene in pure culture. The four strains significantly enhanced plant growth in the absence of pathogens, as evidenced by increases in plant height and dry weight of inoculated rice seedlings relative to noninoculated rice. Three bacterial strains (S3, S20, and S21) were evaluated in pot bioassays and reduced disease incidence by 50%-73%. Strain S3 was as effective at suppressing disease at the lowest inoculum density (106 CFU/mL) as at higher density (10(8) CFU/mL or undiluted suspension). This study indicates that selected endophytic bacterial strains have potential for control of seedling disease of rice and for plant growth promotion.     

Persistent effects of seedling treatment on growth of sugar beet in pots

Further evidence is provided that the environment of sugar-beet seedlings, or growth substances applied to seedlings, continues to influence growth when the plants are later in other environments. Sugar-beet seeds were germinated at 20 °C in 8, 16 or 24 h photoperiods of constant light intensity, i.e. with different amounts of total radiation. When the seedlings had two leaves (15–18 days old) they were transferred to large pots in the glasshouse. Some seedlings were treated with (2-chloroethyltrimethylammonium chloride) either sprayed on the leaves or applied to the soil, at different times. The treatments affected areas of individual leaves throughout the growing period; plants raised in 24 h photoperiod had the largest leaves, and those in 8 h photoperiod the smallest. Consequently, 24 h plants had most dry matter and 8 h plants least. Plants given most radiation produced leaves fastest and CCC applied early increased the rate, but as the leaves were smaller, except late in 1967, and died sooner, the leaf area duration was less and so yields were less. CCC applied later did not affect leaf production. There was no interaction between amount of radiation and CCC treatment. Twenty-four hour plants had the greatest net assimilation rate (E) early. CCC decreased E early, but increased it later and more when sprayed on the leaves than when applied to the soil. Some factor, possibly pot size, eventually restricted growth and probably diminished the effect of the treatments applied to the seedlings.     

油菜素内酯对毛豆幼苗生长及其抗渍性的影响

试验采用不同浓度油菜素内酯对毛豆幼苗进行叶面喷施处理,测定其在渍水胁迫下对毛豆营养生长和生理特性的影响。结果表明:采用一定浓度的油菜素内酯处理可以促进苗生长、提高根系活力、叶绿素含量、脯氨酸含量和抑制丙二醛增生、降低细胞膜透性,增强了毛豆幼苗对渍水环境的抵抗能力。从叶面喷施后对毛豆的营养指标和生理指标进行综合判断可知:在试验的范围内,以1mL/L油菜素内酯的处理效果为最佳。     

A comparative study of the effects of abscisic acid and methyl jasmonate on seedling growth of rice

The effects of abscisic acid (ABA) and methyl jasmonate (MJ) on growth of rice seedlings were compared. The lowest tested concentration of ABA and MJ that inhibited seedling growth was found to be 4.5 and 0.9 µM, respectively. Growth inhibition by ABA is reversible, whereas that by MJ is irreversible. GA₃ was found to be more effective in reversing inhibition of shoot growth by ABA than by MJ. KCl partially relieved MJ-inhibited, but not ABA-inhibited, growth of rice seedlings. The beneficial effect of K⁺ on growth of rice seedlings in MJ medium could not be replaced by Li⁺, Na⁺ or Cs⁺. MJ treatment caused a marked release of K⁺ into the medium. In order to understand whether cell wall-bound peroxidase activity was inversely related to rice seedling growth, effects of ABA and MJ on cell wall-bound peroxidase activity were also examined. Results indicated that both ABA and MJ increased cell wall-bound peroxidase activity in roots and shoots of rice seedlings. Although MJ (4.5 µM) was less effective in inhibiting root growth than ABA (9 µM), MJ was found to increase more cell wall-bound peroxidase activity in roots than ABA.     

Nondwarf rice seedling bioassay for gibberellins

The use of nondwarf rice (Oryza sativa L.) cultivars treated with uniconazole as test plants for gibberellin (GA) bioassay instead of Tan-ginbozu dwarf rice variant was investigated. The sensitivity of six nondwarf rice cultivars to GAs was increased substantially by treatment of the seeds with uniconazole. The minimum detectable dose of a GA in the nondwarf cultivars treated with uniconazole was 1- to 1/10-fold of that in the nontreated Tanginbozu and 3- to 10-fold of that in uniconazole-treated Tanginbozu. The relative activity of several GAs on treated nondwarf rice cultivars was not largely different from that to Tan-ginbozu. Considering that seeds of nondwarf rice are available commercially, the nondwarf rice seedling assay would be useful as a simple assay for systematic analysis of GAs, and also as a routine teaching tool in high schools and universities.