黑果枸杞种子萌发及幼苗生长对盐胁迫的响应

研究不同浓度(0、1、2、3、6、9、14、18g.L-1)的盐溶液(NaCl、MgSO4、盐渍土壤)对河西走廊中部荒漠边缘的黑果枸杞种子吸胀、萌发和幼苗生长的影响,并观察胁迫解除后种子的反应。结果表明:黑果枸杞种子吸胀速率随NaCl、MgSO4和土壤溶液浓度的增大呈先升后降的趋势,吸水速度随胁迫时间的延长而减慢;种子萌发率随3种盐浓度的增大而降低,盐胁迫解除后种子仍具有较高的萌发率;发芽指数、活力指数、根长、下胚轴随3种盐浓度的增大而降低或先升后降,根轴比随盐胁迫的增强先升后降;随3种盐浓度的增大,种苗损害率增大,3种盐的胁迫效应依次NaCl>MgSO4>盐渍土壤溶液。黑果枸杞种子萌发和幼苗生长对NaCl胁迫较为敏感,其耐受的临界阈值是6g.L-1;种子萌发能耐受较高浓度的MgSO4的胁迫,幼苗生长对MgSO4胁迫较敏感,其耐受的临界阈值是9g.L-1;种子萌发和幼苗生长对生境盐渍土壤具有较强的耐受能力和适应性。     

Chilling Sensitivity of Photosynthetic Oil-Seedlings

Seed germination and seedling emergence are particularly sensitiveto low temperatures in oil-seed genera in which lipids are themain seed storage material, e g cotton, corn, cucumber, andwatermelon Growth of photosynthetic seedlings of oil-seed generais also significantly affected by suboptimal temperatures. Aphotosynthetic seedling growth system used to demonstrate suboptimaltemperature stress effects in cotton was modified to monitorthe effects of temperatures from 10 to 35 ? upon the roots andaerial portions of cucumber, cantaloupe, and watermelon seedlings.Non-destructive measurements of fresh weights and the relativewater contents of the roots and shoots of seedlings grown at30 ? and at non-optimal temperatures, as well as chilled seedlingsreturned to 30 ? for one day, indicated significant intra-genencdifferences in temperature sensitivity and relative root andshoot water status of both the chilled seedlings and those recoveringfrom thermal stress The capacity to return to normal water statusand resume growth differed between and within species and wascorrelated with recommendations for chilling tolerance Key words: Temperature, water stress, photosynthetic seedling     

Do mycorrhizal network benefits to survival and growth of interior Douglas-fir seedlings increase with soil moisture stress?

Facilitation of tree establishment by ectomycorrhizal (EM) networks (MNs) may become increasingly important as drought stress increases with climate change in some forested regions of North America. The objective of this study was to determine (1) whether temperature, CO(2) concentration ([CO(2)]), soil moisture, and MNs interact to affect plant establishment success, such that MNs facilitate establishment when plants are the most water stressed, and (2) whether transfer of C and water between plants through MNs plays a role in this. We established interior Douglas-fir (Pseudotsuga menziesiivar.glauca) seedlings in root boxes with and without the potential to form MNs with nearby conspecific seedlings that had consistent access to water via their taproots. We varied temperature, [CO(2)], and soil moisture in growth chambers. Douglas-fir seedling survival increased when the potential existed to form an MN. Growth increased with MN potential under the driest soil conditions, but decreased with temperature at 800 ppm [CO(2)]. Transfer of (13)C to receiver seedlings was unaffected by potential to form an MN with donor seedlings, but deuterated water (D(2)O) transfer increased with MN potential under ambient [CO(2)]. Chlorophyll fluorescence was reduced when seedlings had the potential to form an MN under high [CO(2)] and cool temperatures. We conclude that Douglas-fir seedling establishment in laboratory conditions is facilitated by MN potential where Douglas-fir seedlings have consistent access to water. Moreover, this facilitation appears to increase as water stress potential increases and water transfer via networks may play a role in this. These results suggest that conservation of MN potential may be important to forest regeneration where drought stress increases with climate change.     

疏花水柏枝幼苗生物量与构件对模拟土壤地下水位变化的响应

通过模拟不同地下水位的方法,对疏花水柏枝（Myricaria laxiflora（Franch.）P.Y.Zhang et Y.J.Zhang）一年生幼苗在不同条件下地上与地下部生物量及构件的变化进行测定,分析幼苗生长对地下水位变化的响应。结果显示：随着地下水位的降低,疏花水柏枝幼苗的生长特征指标均呈先增加后减少的趋势,其中地上、地下部分生物量的最高值分别为0.0438、0.0100 g,最低值分别为0.0177、0.0026 g。幼苗地上部生物量在-10 cm处理水平最高;地下部生物量在-15 cm处理水平最高。幼苗直径、根表面积、株高、主根长度、根体积、一级枝数、二级枝数等指标也分别在-10 cm或-15 cm处理水平达到最高值。疏花水柏枝幼苗主要构件的生长与地下水位的变化存在显著相关性。主成分分析结果表明,幼苗的地下部分更容易受到土壤地下水位变化的影响,幼苗性状症候群随地下水位的变化而发生移动,说明该物种幼苗在不同地下水位时的生长投资策略具有较大差异。     

The Effect of Age, Pre-conditioning, and Water Stress on the Transpiration Rates of Douglas-Fir (Pseudotsuga menziesii) Seedlings of Several Ecotypes

Seedlings of Douglas-fir from seed of a number of mesic and xeric origins were grown in growth chambers and a nursery to various ages up to 16 weeks. Measurements were made to determine the effect of seedling age, growth chamber and nursery pre-conditioning, and seed source on transpiration rates under closely controlled laboratory conditions. Additional experiments were conducted on seedlings of two contrasting ecotypes to determine the effect of different pre-conditioning combinations of plant and soil water potential on seedling transpiration rates. Results show that well-watered seedlings of two mesic ecotypes show no decline in transpiration rates per unit leaf area up to 16 weeks of age while corresponding seedlings of three exeric ecotypes do decline. The growth chamber pre-conditioning results in lower seedling transpiration rates and more decline in seedling transpiration rates with increasing plant water stress than for nursery pre-conditioning. In a similar way, the xeric ecotype seedlings have more decline in transpiration rates with increasing plant water stress than do the mesic ecotype seedlings. Soil water potential influences transpiration rates through pre-conditioning effects. Seedlings which have experienced prior soil moisture stress decrease transpiration more in response to low plant water potentials than do plants which have experienced no soil moisture stress. These behavioral characteristics illustrate adaptive means by which seedlings conserve water through the interaction of genetic and preconditioning mechanisms.     

Cold tolerance in tomato. II. Early seedling growth of Lycopersicon spp.

Hypocotyl and root growth elongation of etiolated seedlings was measured non-destructively for the wild tomato accessions LA 460 ( Lycopersicon chilense Dun.), PI 126435, PI 127831 and PI 127832 ( L. peruvianum Mill.) and controls PI 120256 and T3 ( L. esculentum Mill.) on slant boards at 10, 15 and 20°C. Both hypocotyl and root elongation over time were fitted by a logistic growth function with three parameters estimated for each seedling by non-linear least squares regression. Analysis of variance of these equation parameters indicated linear decreases of both hypocotyl and root growth rate parameters with temperature. All four wild accessions maintained greater hypocotyl growth rate parameters at 10°C than the fast-germinating cultivated accession PI 120256, but not significantly greater than T3. Hypocotyl growth rates of the wild accessions were less inhibited at 10°C relative to 20°C than were either cultivated accession. These results suggest that these wild accessions have greater chilling tolerance than cultivated controls for early seedling growth, and may have potential use for genetically improving emergence times for tomatoes sown in cold soil.     

Water stress induced by PEG decreases the maximum growth pressure of the roots of pea seedlings

Roots of plants growing in dry soil often experience large mechanical impedance because the decreased soil water content is associated with increased in soil strength. The combined effect of mechanical impedance and water stress hinders the establishment of seedlings in many soils, but little is known about the interaction between these two stresses. A method has been designed that, for the first time, measured the maximum axial force exerted by a root growing under controlled water stress. Using this technique the axial force exerted by a pea radicle was measured using a shear beam, while the seedling was suspended in an aerate solution of polyethylene glycol 20 000 at osmotic potentials between 0 and -0.45 MPa. The maximum growth force was then divided by the cross-sectional area of the root to give the maximum axial growth pressure. The value of maximum axial growth pressure decreased linearly from 0.66 and 0.35 MPa as the osmotic potentials of the solution of PEG decreased from 0 to -0.45 MPa. In dry soil, therefore, the maximum strength of soil that a root can penetrate is decreased because of the decrease in maximum growth pressure. The elongation rates of unimpeded roots were similar whether the roots were subject to either a matric potential in soil or to an osmotic potential in a solution of PEG.Key words: Pisum sativum L, pea, mechanical impedance, axial growth pressure, water stress, PEG 20 000.      

土壤湿度对香樟幼苗根系生长和构型的影响

以1年生香樟(Cinnamomum camphora)幼苗为试材,设置对照组(CK)、中度干旱处理(M)、重度干旱处理(S)三个处理,比较不同土壤湿度下香樟幼苗不同时期地上部分生长和根系构型,探究香樟幼苗根系对不同土壤湿度的适应性及其耐旱机制。结果表明,中度和重度干旱处理组的香樟根系及地上部分干物质积累、根系长度、根系表面积、根系直径和根尖数均显著小于对照组(P<0.05)。同时干旱显著增加香樟幼苗的根系拓扑指数,降低香樟根的分形维数和平均分枝角度(P<0.05)。可见土壤湿度程度及处理时间显著影响香樟根系的生长及在土壤中的布局。较低土壤湿度可显著抑制根长的延长、根表面积扩大和根的增殖,且随着土壤湿度的继续降低以及处理时间延长,香樟幼苗根系的生长受到水分亏缺的抑制作用加重,根系建成成本增高的同时,根系分枝的复杂性降低,根系必须通过朝着更陡、更深的方向生长伸长来提高水分吸收效率。建议在园林绿化工程养护过程中制定科学的水分管理策略,以满足香樟生长过程中对土壤水分的需要。     

Pre-treatment of seeds with static magnetic field ameliorates soil water stress in seedlings of maize (Zea mays L.)

The effect of magnetic field (MF) treatments of maize (Zea mays L.) var. Ganga Safed 2 seeds on the growth, leaf water status, photosynthesis and antioxidant enzyme system under soil water stress was investigated under greenhouse conditions. The seeds were exposed to static MFs of 100 and 200 mT for 2 and 1 h, respectively. The treated seeds were sown in sand beds for seven days and transplanted in pots that were maintained at -0.03, -0.2 and -0.4 MPa soil water potentials under greenhouse conditions. MF exposure of seeds significantly enhanced all growth parameters, compared to the control seedlings. The significant increase in root parameters in seedlings from magnetically-exposed seeds resulted in maintenance of better leaf water status in terms of increase in leaf water potential, turgor potential and relative water content. Photosynthesis, stomatal conductance and chlorophyll content increased in plants from treated seeds, compared to control under irrigated and mild stress condition. Leaves from plants of magnetically-treated seeds showed decreased levels of hydrogen peroxide and antioxidant defense system enzymes (peroxidases, catalase and superoxide dismutase) under moisture stress conditions, when compared with untreated controls. Mild stress of -0.2 MPa induced a stimulating effect on functional root parameters, especially in 200 mT treated seedlings which can be exploited profitably for rain fed conditions. Our results suggested that MF treatment (100 mT for 2 h and 200 for 1 h) of maize seeds enhanced the seedling growth, leaf water status, photosynthesis rate and lowered the antioxidant defense system of seedlings under soil water stress. Thus, pre sowing static magnetic field treatment of seeds can be effectively used for improving growth under water stress.     

Water Deficit and Abscisic Acid Cause Differential Inhibition of Shoot versus Root Growth in Soybean Seedlings : Analysis of Growth, Sugar Accumulation, and Gene Expression

Roots often continue to elongate while shoot growth is inhibited in plants subjected to low-water potentials. The cause of this differential response to water deficit was investigated. We examined hypocotyl and root growth, polysome status and mRNA populations, and abscisic acid (ABA) content in etiolated soybean (Glycine max [L.] Merr. cv Williams) seedlings whose growth was inhibited by transfer to low-water potential vermiculite or exogenous ABA. Both treatments affected growth and dry weight in a similar fashion. Maximum inhibition of hypocotyl growth occurred when internal ABA levels (modulated by ABA application) reached the endogenous level found in the elongating zone of seedlings grown in water-deficient vermiculite. Conversely, root growth was affected to only a slight extent in low-water potential seedlings and by most ABA treatments (in some, growth was promoted). In every seedling section examined, transfer of seedlings into low-water potential vermiculite caused ABA levels to increase approximately 5- to 10-fold over that found in well-watered seedlings. Changes in soluble sugar content, polysome status, and polysome mRNA translation products seen in low-water potential seedlings did not occur with ABA treatments sufficient to cause significant inhibition of hypocotyl elongation. These data suggest that both variation in endogenous ABA levels, and differing sensitivity to ABA in hypocotyls and roots can modulate root/shoot growth ratios. However, exogenous ABA did not induce changes in sugar accumulation, polysome status, and mRNA populations seen after transfer into low-water potential vermiculite.     

Root Regeneration and Plant Water Status of Pinus radiata D. Don Seedlings Transplanted to Different Soil Temperatures

The regeneration and configuration of new roots on transplanted8 month old Pinus radiata D. Don seedlings were measured inrelation to soil temperature and time after transplanting. Theeffects of root wrenching and nutrition on root regenerationwere compared. Low soil temperature adversely affected the initiationand elongation of new roots. The branching and morphology ofthe new roots were also influenced by soil temperature. Theprocesses of initiation and elongation are greatly retardedbelow a critical root temperature between 11 and 14 ?C. Wrenchingand fertilization stimulated new root growth at low temperatures.There is a close interrelationship between the constituent partsof the network which forms the new root system. The first-orderlaterals on transplants are critical as a basic framework forextension and production of second-order laterals which formthe major part of the regenerating root system. Needle water potential was closely related to the new root growth.The water stress experienced by the transplants for severalweeks after planting was due primarily to the suppressive effectof low soil temperature on root regeneration. Wrenched plantswere less water-stressed than unwrenched plants. Field measurements confirmed the finding from controlled experimentsthat, in southern Australia, the low soil temperature in theplanting season imposes a major restriction on early root regenerationwhich in turn inflicts water stress in transplants. This needsto be considered during the planning of planting and fertilization.     

云南干热河谷水库气候效应对车桑子幼苗生长发育的影响及其作用机制

干热河谷地区水电站建设对当地植被的潜在影响是一个值得关注的生态学问题。车桑子是当地植被灌木层的主要成分,开展水库气候效应对车桑子生长、发育影响的研究具有现实价值。以车桑子的实生幼苗为材料,将土壤含水量控制为13%、7%和1.5%,空气湿度控制为50%、65%和75%,从幼苗生长、构件发育、根系发育、生物量分配等方面研究了降水减少和大气湿度增加的气候效应对车桑子的影响,通过叶绿素含量、Fv/Fm、丙二醛(MDA)含量和叶片可溶性糖含量等指标,从光合系统特性、膜质过氧化和渗透调节3个方面研究了车桑子的受损与适应机制。结果表明,土壤干旱能够抑制车桑子幼苗高生长和根系发育的各项指标,并促进生物量向根系分配;当大气湿度增加时,幼苗高生长和根长虽呈增加趋势,但生物量积累、根系发育指标及RMR却具有单峰效应,显示空气湿度过高时对其生长发育具有抑制作用。综合而言,由于大气湿度增加能够部分补偿土壤的干旱效应,干热河谷区水库建设的气候效应不会对车桑子幼苗的生长和发育产生重要影响。结果还表明,土壤干旱和大气湿度变化对叶绿素含量无影响,土壤水分胁迫和空气湿度下降导致Fv/Fm显著下降,说明光合电子传递链受损是车桑子光合抑制的主要原因;土壤水分胁迫导致MDA含量升高,说明细胞膜质过氧化是车桑子幼苗受损的重要机制;而土壤干旱导致叶片可溶性糖含量升高,说明车桑子幼苗具有较好的渗透调节机制。研究结果对评估干热河谷区水电站建设对植被的影响具有参考价值。     

Soil temperature and flooding effects on two species of citrus

Summary Rough lemon (Citrus jambhiri Lush.) and sour orange (C. aurantium L.) seedlings were grown at constant soil temperatures of 16, 24, and 33 C for 3 months. Shoot and root growth of rough lemon was greatest at 33 C while growth of sour orange was greatest at 24 C. There were no significant effects of soil temperature on shoot: root ratio, leaf water potential or stomatal conductance. The hydraulic conductivity of intact root systems of both species was highest when seedlings were grown at 16 C. Thus, acclimation through greater root conductivity at low soil temperature may have compensated for decreased root growth at 16 C and negated effects of soil temperature on plant water relations. Half the plants growing at each soil temperature were subsequently flooded. Within 1 week, the soil redox potential (Eh) dropped below zero mV, reaching a minimum Eh of –250mV after 3 weeks of flooded conditions. Flooded plants exhibited lower root conductivity, a cessation of shoot growth, lower leaf water potentials, lower stomatal conductances, and visual sloughing of fibrous roots. Decreases in root conductivity in response to flooding were large enough to account for the observed decreases in stomatal conductance.Florida Agricultural Experiment Stations Journal Series No. 4080.     

Hypocotyl of seedlings of the large-seeded species Araucaria angustifolia: an important underground sink of the seed reserves

Araucaria angustifolia exhibits cryptogeal germination, where the root–hypocotyl axis emerges first and penetrates into the soil. In Araucaria bidwillii, the whole process of transferring reserves from the seed to the seedling takes place before shoot emergence, and there is a major storage of these reserves in the underground hypocotyl, which assumes a tuberous form. In A. angustifolia, the shoot emerges before seed reserves are depleted. Though it does not grow like a tuber, the hypocotyl of A. angustifolia grows thicker than the adjacent taproot during initial growth, and we hypothesize that it may act as a major sink for seed reserves during this stage. The study tests this hypothesis by evaluating changes in the mass of different plant parts during initial growth. Four harvests were conducted during a ~6-month period to compare the dry mass of different fractions (attached seed, seedling, its shoot and root and the hypocotyl) of seedlings growing under darkness and high light. While seed reserves were still being depleted, the hypocotyl mass showed an initial increase and then a reduction. This was more abrupt when light was available. After seed mass had stabilized, the mass of the hypocotyl continued to decrease in the dark-grown seedlings, but showed a second increase in the light-grown ones. Results confirm the hypothesis that the hypocotyl represents a major sink for the seed reserves of A. angustifolia, acting as an underground storage structure for the growing seedling. Its reserves seem to be important for sustaining initial shoot growth and might also act as a storage sink for photosynthates.     

Competitive suppression of Quercus douglasii (Fagaceae) seedling emergence and growth

Reduced recruitment of blue oak (Quercus douglasii) seedlings in California grasslands and woodlands may result from shifts in seasonal soil water availability coincident with replacement of the native perennial herbaceous community by Mediterranean annuals. We used a combination of container and field experiments to examine the interrelationships between soil water potential, herbaceous neighborhood composition, and blue oak seedling shoot emergence and growth. Neighborhoods of exotic annuals depleted soil moisture more rapidly than neighborhoods of a perennial grass or "no-neighbor" controls. Although effects of neighborhood composition on oak seedling root elongation were not statistically significant, seedling shoot emergence was significantly inhibited in the annual neighborhoods where soil water was rapidly depleted. Seedling water status directly reflected soil water potential, which also determined the extent and duration of oak seedling growth during the first year. End-of-season seedling height significantly influenced survival and growth in subsequent years. While growth and survival of blue oak seedlings may be initially constrained by competition with herbaceous species, subsequent competition with adult blue oak trees may further contribute to reduced sapling recruitment.     

Rapid root extension during water pulses enhances establishment of shrub seedlings in the Atacama Desert

Questions: (1) What is the water threshold for shrub seedling establishment in arid scrubland? (2) How do seedling root growth morphological traits affect the water threshold required for seedling establishment? Location: Arid scrubland, Atacama Desert, north‐central Chile. Methods: We conducted a field experiment with nine native shrub species under a gradient of simulated rainfall to test if species with deep root architecture have higher seedling survival rates and establish more successfully during water pulses. Results: Seedling survival rate was very low; only 2% of the 12 150 planted seedlings survived the first summer drought. Seedling survival required at least 206 mm of water, which is twice the average rainfall and roughly equivalent to the precipitation during an ENSO (El Niño Southern Oscillation) event in this region. Seedling survival at the onset of the summer drought was best explained by leaf habit, root length and initial seedling size. However, only Senna cumingii seedlings survived through the first year. S. cumingii seedlings had distinctively longer roots than the other shrub species, enabling them to reach moister soil layers. Conclusions: Water conditions resembling rainy years enhance shrub seedling establishment in the Atacama Desert, but the effects of higher water availability are strongly dependent on the shrub species. Rapid and deep rooting appears to be a very important functional trait for successful first‐year survival in this arid system where water availability is highly episodic.     

岷江干旱河谷土壤水、氮和磷对小马鞍羊蹄甲幼苗生长的影响

资源阈值对植物的影响是恢复生态学的重要议题.通过近似模拟岷江干旱河谷自然干旱条件下水、氮和磷的阈值,设计析因实验,研究了一个生长季节内小马鞍羊蹄甲幼苗生长、生物生产量、资源利用效率和存活率的变化.结果表明：高水（40%田间持水量）、高磷（24 mg P·kg^-1）和低氮（100 mg N·kg^-1）处理分别促进了幼苗生长,增加了生物生产量,提高了存活率和水分利用效率,氮磷交互作用显著,水分和养分交互作用不明显.高氮（240 mg N·kg^-1）有强烈的负效应,高磷可以增大根面积、根长和根生物量,提高对氮和磷的吸收,缓解高氮的抑制作用.养分利用效率和幼苗根茎比呈显著正相关,并保持相对稳定.高水、高磷和低氮耦合有效地促进了幼苗的生长,而低水、低磷和高氮耦合则明显抑制了幼苗生长.     

Natural regeneration of Pinus resinosa on burned and unburned sites in Newfoundland

Abstract. Natural regeneration of Pinus resinosa (red pine) seedlings around mature trees was studied in burned and unburned stands. Growth inhibitory effects of the forest organic matter on red pine seedlings was tested by a stair-step experiment using leachate of forest soil monoliths and also by a seed germination bio-assay using forest floor substrates. To test if higher burning temperatures can remove the allelopathic effects of red pine-Kalmia organic matter, a laboratory bio-assay was conducted by germinating red pine seeds on the organic matter burned at 200, 400, 600 and 800°C. Deposition of dry needles and a thick duff layer under red pine stands affected seedling establishment. Red pine seedling establishment increased with the decreasing thickness of duff layer away from the stump of the seed-bearing trees. Wildfire helped in removing the duff layer and increased seedling establishment. A high fuel load within a 0 - 1 m radius around the tree stump caused a deep burn of the organic matter including part of the soil seed reserve. On a burned-over surface, more seedlings established in a band between 1 and 2 m around the stump than inside and outside the band. Primary root growth of red pine was severely inhibited when the seedlings were grown in unburned forest floor organic matter where Kalmia was the principal understory species. Water leachate of a Pinus resinosa-Kalmia soil monolith was inhibitory to red pine seedling growth. In greenhouse conditions, the seedlings grew well in burned-over soil from a Pinus resinosa stand. Burned organic matter from a red pine forest showed an increase in pH with a burning temperature of 600°C. Primary root growth of red pine seedlings was similarly increased with increasing temperature up to 600°C; at higher temperatures the root length of seedlings did not increase any further.     

水分胁迫对春播玉米苗期生长及其生理生化特性的影响

采用盆栽试验,以‘蠡玉18'玉米单交种为供试材料,设置充分供水(CK)、轻度水分胁迫(LS)、中度水分胁迫(MS)和重度水分胁迫(SS)4个水分处理水平,研究了水分胁迫对春播玉米苗期保护酶活性和生长的影响,以探讨土壤水分胁迫对玉米苗期生长发育及其生理过程的影响机制.结果表明:(1)随着水分胁迫程度的加剧,玉米幼苗的生物量显著下降,根冠比、根系活力和脯氨酸含量增加,且水分胁迫对玉米幼苗地上部生物量的抑制作用更大;可溶性蛋白含量差异不明显,MDA含量波动变化.(2)随着水分胁迫时间的延长,根冠比、根系活力和植株脯氨酸含量先升高后降低,可溶性蛋白含量呈先下降后升高的趋势;玉米幼苗叶片和根系MDA积累波动变化,而叶片MDA含量始终高于根系.(3)在水分胁迫初期,玉米叶片中CAT活性较SOD、POD响应更敏感;玉米苗期根系在中度水分胁迫下主要依赖CAT来降低氧化危害,而在重度水分胁迫下前期主要依赖CAT、后期通过CAT和POD的共同作用来降低氧化伤害;水分胁迫条件下,叶片和根系POD同步降低氧化伤害,而SOD和CAT在叶片和根系间存在互补作用.研究表明,在不同程度的水分胁迫条件下,玉米幼苗的生长受到一定程度的抑制,但其能够通过调节自身的保护酶活性和渗透调节物质含量来减轻干旱伤害,维持植株的正常生理代谢功能.     

Regional growth patterns in the hypocotyls of etiolated and green cress seedlings in light and darkness

Abstract. A system is described whereby seedling development can be analysed in terms of growth rates of specific 1 mm regions of the hypocotyl. The technique involves time-lapse photography of marked hypocotyls in a specially designed chamber which accommodates seedlings in various orientations with respect to gravity, and under irradiation regimes differing in light quality, quantity and direction. The results of a preliminary study of the upward growth of etiolated or green cress seedlings in darkness or overhead while light are reported. Highest growth rates in etiolated seedlings were observed in zones in the upper one-third of ihe hypocotyl. In green seedlings, growth was more prominent within the subapical zones. Light further restricted growth of the median and basal zones in both types of seedling. However, in their immediate responses to the onset of irradiation, green and etiolated seedlings differed markedly. In etiolated seedlings, recovery of growth at the apex was accompanied by the development of inhibition in the median-basal regions; green seedlings showed a transient inhibition of growth in the apical zone together with a strong immediate inhibition in the median-basal regions.