Effect of Temperature on Phytochrome-mediated Responses in Seedlings of Mustard

Anthocyanin synthesis, hair formation, and the synthesis of ascorbic acid oxidase are all phytochrome-mediated reactions occurring in the hypocotyl of mustard (Sinapis alba L.). An investigation was conducted into the effects of temperature on the light promotion of these three photoresponses. When given prior to a light exposure there was either no difference between a 20 and 30 C temperature treatment, or the 30 C treatment resulted in a greater photoresponse. When given subsequent to a light exposure 20 C was far more effective in promoting the responses than was a 30 C treatment. These results are in accordance with the known effects of low temperature on delaying phytochrome-far red absorbing form (Pfr) destruction, thus resulting in more Pfr being available to promote the responses. The difference between temperature treatments was greatest following a short light exposure, and much smaller following a long light exposure. When light was given as intermittent illumination the difference between subsequent temperature treatments was much less than when the same amount of light was given as continuous illumination.     

Light-Dependence of Phospholipase D Activity in Oat Seedlings

The effect of light on the activity of phospholipase D (PLD) in oat (Avena sativa L.) seedlings and the dependence of this enzyme activity on the regime of their illumination were studied. The PLD activity in etiolated seedlings was 1.5–2.0-fold higher than in green plants. The illumination of etiolated seedlings with white light resulted in a decrease in PLD activity to its level in the seedlings grown under light. In contrast, the transfer of green seedlings to darkness enhanced the activity of the enzyme up to its level in etiolated seedlings. The illumination of etiolated seedlings with red light inhibited the PLD as well. It was shown that this photoeffect decreased with seedling aging and correlated with a phytochrome content in plants. Far-red light reversed the effect of red light. The involvement of phytochrome in the control of the PLD activity is discussed.     

Amyloplast Size and Number in Gravity-compensated Oat Seedlings

Gravity compensation by the horizontal clinostat increases the diameter of amyloplast starch grains of oat (Avena sativa cv. Victory) coleoptile parenchyma cells, as compared to vertically rotated and stationary controls. In dark-grown coleoptile tip parenchyma cells, measured starch grain sizes exhibit a wide distribution of diameters, from approximately 1.5 to approximately 8.0 mum, but fall into three prominent diameter classes. The compensated tissues from both the tip and the subapical region have more starch grains in the larger, and fewer in the smaller size classes, compared to controls. The total number of starch grains per cell, the total plastid number per cell, and cell volume are unaffected by gravity compensation. Amyloplasts with large starch grains are denser, as well as larger in diameter, than those with smaller starch grains. The amyloplast is considered as a geosensor with an active metabolic role in the geotropic transduction mechanism.     

Photoregulation of the Endogenous cGMP Content in Oat Seedlings

The concentration of cGMP in the tissues of oat (Avena sativaL.) seedlings was shown to depend on seedling age and the light regime of their growth. The level of cGMP in the etiolated seedlings was lower than in the green ones and declined with seedling age. Red and blue light recognized by phytochrome and cryptochrome, respectively, affected the cGMP content. The effectors of cGMP metabolism, guanylin, protoporphyrin IX, and zaprinast, elevated the cGMP content in tissue extracts from oat seedlings.     

Phytochrome-mediated Induction of Phenylalanine Ammonia-Lyase in Mustard Seedlings: A Contribution to Eliminate Some Misconceptions

The present report shows that the effect of red and far red light on the synthesis of phenylalanine ammonia-lyase can be ascribed to the action of phytochrome Pfr. This is true not only for short term irradiation but also for the action of continuous far red light. In the latter case, the model worked out by Hartmann implicating some excited species of phytochrome has to be taken into account.     

Density of Microbodies on Sucrose Gradients during Phytochrome-mediated Glyoxysome Peroxisome Transformation in Cotyledons of Mustard Seedlings

The microbodies extracted from the cotyledons of mustard seedlings (Sinapis alba L.) form two bands (at 1.18 kilograms per liter together with the mitochondria, and at 1.24 kilograms per liter) on conventional isopycnic sedimentation density gradients. The artifactual co-banding of part of the microbodies with the mitochondria can be prevented by using flotation gradients. Using this procedure, a systematic investigation revealed no effect of seedling age and irradiation (far red or white light) on the density of the microbody population (1.242 ± 0.002 kilograms per liter). Thus, although light, through phytochrome, induces conspicuous changes in their enzyme composition the microbodies appear as a homogeneous population of constant density on a sucrose gradient.     

Photoregulation of beta-Tubulin mRNA Abundance in Etiolated Oat and Barley Seedlings

The effect of light on the abundance of β-tubulin mRNA was measured in etiolated Avena sativa L. and Hordeum vulgare L. seedlings. Slot blot analysis employing an oat β-tubulin cDNA clone was used to measure β-tubulin mRNA levels. White light induced a 45% decrease in oat β-tubulin mRNA abundance by 2 hours after transfer. A saturating red light pulse induced 40 and 55% decreases in β-tubulin mRNA levels in oats and barley, respectively. Recovery of β-tubulin mRNA levels was observed after a red light pulse but not after transfer to continuous white light. The red light induced decrease in oat β-tubulin mRNA abundance was not reversible by a subsequent far-red light treatment. The mesocotyl portion of etiolated oat seedlings exhibited a more dramatic decrease in β-tubulin mRNA abundance in response to red light than did the coleoptile portion. The results indicate that the well-documented effects of red light on the growth of etiolated seedlings are accompanied by changes in the expression of the β-tubulin genes.     

Rapid Phytochrome-mediated Changes in Adenosine 5'-Triphosphate Content of Etiolated Bean Buds

This study was designed to determine the effects of red and far red irradiation on ATP metabolism in etiolated bean buds (Phaseolus vulgaris L. var. Red Kidney). Compared to dark controls, red irradiated buds show an initial decline in ATP content at 15 seconds following a 5-minute irradiation. ATP content then rapidly rises to a peak at 1 minute, and then slowly returns to the baseline. The 1-minute promotion of ATP content is red/far red reversible. Acetylcholine does not appear to mimic red light in this system; it causes a marked decrease in ATP content.     

The Dominant Influence of Nitrogen on Growth Correlation in Etiolated Oat Seedlings

A nutritive hypothesis is put forward to account for the inhibitoryeffect of carbon dioxide, and of sucrose, on the elongationof the coleoptile and leaves of etiolated oat seedlings. Growthdepends, it is assumed, on the availability of nitrogen, andthe way in which the supply is diminished by these treatmentshas been elucidated. Three factorially arranged experimentswere carried out to provide the necessary growth data and observationswere also made of the distribution throughout the seedlingsof dry-weight, of sugars and of nitrogen. Additionally, thequantity of reserves, and of nitrogen, flowing into the seedlingduring growth have been determined. The dependence of coleoptileand leaf growth on the supply of nitrogen has been demonstratedand also the dependence of the amount of nitrogen transferredon the total weight of translocate. The growth inhibition canthen be explained on the assumption that treatment with carbondioxide and sucrose decreases the weight of reserves translocatedfrom the endosperm and so reduces the amount of nitrogen passinginto the seedling. Consumption of nitrogen by the mesocotyland roots, however, is not correspondingly reduced; the coleoptilesand leaves, perforce, bear the entire shortage and their growthis checked. These results may also be utilized to explain the transientgrowth promotion of the coleoptile and leaves brought aboutby illumination and heating, so avoiding the need to postulatechanges in auxin metabolism. The importance of the nitrogen supply during germination isdiscussed.     

Regulation of Phospholipase D Activity by Light and Phytohormones in Oat Seedlings

The effect of synthetic analogs of phytohormones and red light absorbed by phytochrome on the phospholipase D activity (PLD) was studied in oat (Avena sativa L.) seedlings. ABA manifested a short-term stimulating effect on PLD activity in the green seedlings and inhibited phospholipase activity in the etiolated plants. Kinetin inhibited enzyme activity in the etiolated seedlings and did not affect its activity in light. GA did not markedly affect PLD activity in the etiolated plants and activated this enzyme in the green seedlings. Finally, IAA did not affect the enzyme activity. The relationship of the regulatory effects of phytohormones and light on PLD activity is discussed.     

Role of Membrane-bound, Fixed-charge Changes in Phytochrome-mediated Mung Bean Root Tip Adherence Phenomenon

The movement of cells and cell fragments in an electric field provided a means for determining the nature of cellular surface charges. We found that changes in ionic strength and particularly changes in Ca²⁺ and H⁺ in the bathing medium cause changes in the surface charges on the root cap cells in the absence of red light. Red light-induced charge changes are demonstrable only on root cap cells and are reversible with far red light. By osmotically separating the membrane from the wall, we demonstrated that both light-induced and ionically mediated charge changes are associated with the cell membrane and not the cell wall.     

A Study of the Growth and Photoperceptivity of Etiolated Oat Seedlings

The photoperceptivity of intact oat seedlings has been observedafter pretreating them for 3 days in darkness with a numberof substances—copper and manganese ions, EDTA, copper-glycine,glycine, nitrates, indoleacetic acid, ethanol, and carbon dioxide. None enhanced photosensitivity; carbon dioxide and ethanol reducedit. Copper-glycine in darkness promoted mesocoty1 growth and inducedroot formation. The effects of carbon dioxide and ethanol are shown to be identicaland to account for this a speculative proposal is made aboutmaturation. An alternative explanation of the growth of the mesocotyl thenarises. The relationship between maturation and the behaviour of theseedling upon illumination is discussed.     

Manganese Supply in Relation to the Growth and Photosensitivity of Etiolated Oat Seedlings

Evidence has been sought for an interaction between native auxinand manganese in vivo by observing the effect of an excess ofmanganese on the growth and photosensitivity of etiolated oatseedlings. Intact plants were supplied with manganese via theirroots in conjunction with other growth-modifying treatments,glycine, ethanol, carbon dioxide, and nitrates. The data showthat neither growth nor photosensitivity was changed by theadditional manganese; consequently no evidence for the occurrenceof such an interaction was obtained.     

燕麦幼苗单胺氧化酶的热稳定性及催化特性研究

含黄素单胺氧化酶(MAO)在生物体内通过对单胺类物质的氧化脱氨作用生成相应的醛、氨气和过氧化氢。MAO在植物中的研究较少,通过对燕麦幼苗MAO的研究发现,暗条件下生长的燕麦幼苗匀浆内所含MAO活性均高于光照条件,且发芽三天左右的幼苗体内MAO的活性达到峰值(2.5pKat/mg),同时测定不同组织中MAO的活性为:幼芽>幼根>种子。对纯化后的燕麦MAO的热稳定性和催化特性研究表明:燕麦MAO的热稳定性较差,常温下易失活,37℃和50℃下水浴90min后,活性损失分别为50%和75%;燕麦MAO对底物的选择性较强,只对低浓度的苄胺和苯乙胺的氧化具有催化效果,Km分别为265μmol/L和705μmol/L;在对底物的特异性方面与人类MAO B有一定的相似性,但体外催化效率低于黑曲霉MAO和人类MAO B。     

Rapid Hormone-induced Hyperpolarization of the Oat Coleoptile Transmembrane Potential

The effects of the plant growth substances indoleacetic acid (IAA) and fusicoccin on the transmembrane potential of Avena coleoptile cells (at 27-29 C) were studied. Fusicoccin caused hyperpolarization of the membrane potential which started after a lag of less than 20 seconds, and which on average reached -49 mv at an external K(+) concentration of 1 mm and -75 mv at 0.1 mm K(+). IAA caused a hyperpolarization of -25 mv starting after a lag of 7 to 8 minutes. These results suggest that fusicoccin and IAA both activate electrogenic H(+) extrusion.     

Canola and Oat Forage Potential Evaluation in Four Early Planting Dates

Canola and oat forage potential may be affected by climatic conditionswhen sown early. The objective of this study was to evaluate the forage canola andoat potential in four early sowing dates (September 11 and 25; October 9 and 23)during the 2012-2013 and 2013-2014 cycles in Matamoros, Coahuila, Mexico.Growth cycle duration, chemical composition, dry matter (DM), crude protein (CP),and net energy for lactation (NE_L) yields were determined. High temperatures andlong photoperiods affected crops seeded on September 11, accelerating growth andreducing canola (26.6%-31.7%) and oat (15.8%) DM yields. As of September 25,canola cv IMC 205 reached DM yields (7746 kg ha^-1-9276 kg ha^-1) similar to thoseobtained by oat (8115 kg ha^-1-9507 kg ha^-1), while canola cv Hyola 401 obtainedsuch yields only until October 23. Canola chemical composition was better thanthat found in oat, with higher CP, but lower acid detergent fiber (ADF) and neutraldetergent fiber (NDF) contents. Canola equaled oat CP yields (972 kg ha^-1-1215 kgha^-1) in the first sowing date, while in the other three other canola sowings reachedhigher yields (1193 kg ha^-1-1889 kg ha^-1). As for NEL yields, no difference wasobserved between both species. The best sowing date for canola is from September25 on, with CP production advantages over oat.     

燕麦发芽过程中三大营养素的变化

为了丰富燕麦相关产品、充分利用中国现有稀缺的燕麦资源以及最大限度的挖掘裸燕麦的可利用性,对来自陕西的一个裸燕麦品种进行发芽六天的试验,并分析燕麦籽粒在发芽过程中三大营养素和β-葡聚糖含量的变化得出以下结果:在裸燕麦发芽过程中总氮含量和脂肪含量变化不明显,分别下降了0.2%和0.1%,发芽六天后淀粉含量从原种子的63.04%降至52.8%。但是游离氨基酸、可溶性糖和还原糖含量则增加很明显,β-葡聚糖含量相对于原燕麦种子本身含量来说在发芽过后下降幅度也较大,下降了约3%。这一结果说明燕麦发芽后其营养价值增加,但是基于β-葡聚糖功能特性的利用会有所降低。