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1.
PEG胁迫对胡枝子幼苗叶片生理特性的影响 总被引：2，自引：0，他引：2
采用PEG处理人工模拟水分胁迫方法,研究了胡枝子属5种植物2 a生实生苗的抗旱性,并采用主成分分析法和隶属函数法对其抗旱性进行综合评价。结果表明,随着PEG处理浓度的增加,5种胡枝子叶片含水量、相对含水量、自由水和束缚水呈下降趋势;阴山胡枝子和截叶胡枝子的自然水分饱和亏随PEG浓度增加而增大,其余3种胡枝子自然水分饱和亏在PEG浓度为12%时达到最大;SOD、POD和CAT 3种酶活性随PEG浓度增大而逐渐升高,达到峰值后开始下降;MDA含量不断上升;可溶性蛋白质含量先增后降再增;叶片内游离脯氨酸含量持续增大;叶绿素a、b和总叶绿素含量先升后降;5种胡枝子相对电导率总体为持续增大。根据主成分分析对各胡枝子12个指标的隶属函数值进行计算,并求平均值,评价其抗旱顺序。抗旱性由强到弱的顺序为达乌里胡枝子、牛枝子、尖叶胡枝子、截叶胡枝子和阴山胡枝子。 相似文献
2.
There is a great deal of literature on the effects of sand burial upon the survival and growth of desert plants, but the physiological adaption mechanisms of desert plants to sand burial have as yet ra... 相似文献
3.
Effects of drought stress on antioxidant enzyme, photosynthetic
pigment and flavonoid pathway in two desert shrubs 总被引：1，自引：0，他引：1
Antioxidant enzyme activity, photosynthetic pigment content, and free malondialdehyde (MDA), as well as flavonoid content and
the key enzyme activity in the flavonoid pathway were determined in two desert shrubs, Caryopteris mongolica Bunge and
Reaumuria soongorica (Pall.) Maxim. under drought stress. The free MDA content was enhanced during the experimental period,
which may be an indicator of oxidative stress. Superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX)
activities in C. mongholica showed a significant increase during the experiment, but catalase (CAT) activity was slightly decreased.
On the other hand, POD and APX activities showed a significant increase and SOD and CAT activity data had no significant
changes in R. soongorica. APX, SOD, and CAT activities were higher in R. soongorica than in C. mongholica, but MDA content
was lower, indicating that the lower values of MDA were attributed to higher activities of antioxidant enzyme in R. soongorica.
Chlorophyll content decreased significantly in the two shrubs during the experiment, which indicated that there was a photoprotection
mechanism through reducing light absorbance by decreasing pigments content. Caretonoids content increased in C.
mongholica and decreased in R. soongorica. The ratio of Chla/Chlb decreased significantly but caretonoids/Chl revealed a significant
increase in the two shrubs, which could be explained as no decrease of peripheral light-harvesting complexes and a higher
tolerance to drought. Total flavonoid content and the activities of phenylalanine ammonialyase (PAL) and chalcone isomerase
(CHI) showed different changes between C. mongholica and R. soongorica after treatment. These values decreased in R.
soongorica and increased in C. mongholica except for PAL activity. However, anthocyanin content increased in the two shrubs,
indicating that there was a different regulation response in the flavonoid pathway in the two shrubs under drought stress, and anthocyanin
should be an important antioxidant both in the shrubs. Our results demonstrated the different responses of antioxidant
defense and drought tolerance ability between the two shrubs. 相似文献
4.
Michael S. Peek Andrew J. McElrone Irwin N. Forseth 《Journal of Arid Environments》2004,58(4):439-449
Over the course of a day, aridland plants experience a range of incident photosynthetic photon flux (PPF) spanning three orders of magnitude. Rapid photosynthetic responses to changes in PPF have large effects on individual plant carbon gain and water use patterns, hence are important to plant distribution and success. We investigated the response over time of photosynthesis (A), stomatal conductance (g), and inter-cellular CO2 concentration (Ci) to step changes in PPF in a long-lived aridland perennial that typically occurs in two contrasting microhabitats, shade under shrubs of other species and unshaded inter-shrub spaces. An initial rapid response in A and Ci for plants in both microhabitats occurred after abrupt changes in PPF. This was followed by slower changes in these parameters during the rest of the light or dark period. Stomatal conductance responded more gradually to step changes in PPF. The initial increase in A after a dark cycle was significantly greater for plants under shrubs than for plants in inter-shrub spaces, but other changes in A, g and Ci did not differ. We attribute the similar responses in plants from different microhabitats to natural variations in solar radiation and limited selection for differentiation due to population gene pools dominated by plants in the open. Our results support the hypothesis that variable light regimes select for photosynthetic gas exchange processes that closely track changes in incident PPF. Our data also support the hypothesis that gas exchange responses to variable light regimes in aridland plants minimize trade-offs between carbon gain and water loss. 相似文献
5.
Drought is a major production constraint for major fruits and vegetable crops in the tropics.This study was conducted to investigate the effect of limited water supply at three growth stages (vegetative,flowering and fruiting) on the accumulation of proline and soluble sugars in three pepper species.Seeds of the three pepper species,Capsicum chinense Jacq.,C.annuum L.and C.frutescens L.were raised in a nursery and the seedlings were transplanted into seventy two plastic pots arranged in a randomized complete block design with three replicates,25 days after planting.Four water treatments,200 mL of water supplied twice daily (W1),once in every three days (W2),once in every five days (W3),and zero water supplied throughout growing period (W0) were imposed at three vegetative,flowering,and fruiting growth stages.Data were collected on relative water content,free proline and total soluble sugar.Data collected were subjected to analysis of variance and means were separated using Duncan''s multiple range test.Results show that the concentration of proline and soluble sugar in leaves of the three pepper species were found to be remarkable at the different stages of growth in the stressed plants. 相似文献
6.
The seedlings of Halocnermum strobilaceum were cultivated in 0.5% hoagland nutrient solution containing 0.0%, 0.9%, 2.7% and 5.4% of NaCl as well as composite salt (Na+, Ca2+, K+, Si4+) for 20 days; all the contents are in weight ratio. Succulent level, inorganic ions (Na+, K+), organics such as betaine, proline, malondialdehyde, and antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), betaine aldehyde dehydrogenase (BADH) were measured to reveal its salt tolerance mechanism. When the composite salt concentration reaches 5.4%, SOD activity level, and MDA content is five times the control group; when it reaches 2.7%, the succulent level of seedlings, and the content of K+ in roots is nearly two times the NaCl treatment; the dry weight is more than three times the control group; with the NaCl treatment, MDA is three times the contrast; when the salt concentration is 2.7%, POD reaches the maximum. Results indicate that Si4+, K+, and Ca2+ from composite salt in the roots of H. strobilaceum improved the water-holding capacity. The activities of antioxidant enzyme were raised by the accumulation of proline and betaine, which increased the salt tolerance. The absorption of K+ promoted the high ratio of K+/Na+ and alleviated the damage of cell membranes of H. strobilaceum, which is associated with osmotic contents such as betaine and proline. 相似文献
7.
钠盐对冬小麦抗旱性增效作用调控机理的生理生态学分析 总被引：2，自引：0，他引：2
以冬小麦（烟台-2070）为实验材料,苗期对冬小麦进行不同浓度钠盐(NaCl、Na2CO3、Na2SO4)处理,在随后进行的干旱胁迫和复水过程中进行叶片抗逆生理指标变化对比分析,以期探究盐处理在提高小麦抗旱性中的作用和生理调节机理,为未来干旱区农业实施盐水灌溉提供理论依据。实验采用盆栽法,将冬小麦种子盆栽,待长到第7天进行不同浓度钠盐(70 mM, 135 mM, 200 mM, 270 mM)预处理8 d, 然后进行干旱胁迫12 d和复水5 d。分别在盐处理的第4天,第8天,干旱胁迫的第4天,第8天,第12天,以及复水第5天,从不同盐处理中采集冬小麦叶片,分析叶片相对含水量、丙二醛（MDA）、脯氨酸含量及抗氧化酶活力[超氧化物岐化酶（SOD）、过氧化氢（CAT）、过氧化物酶(POD)]的动态变化,同时测定土壤含水量。结果表明,在干旱胁迫过程中,未经盐处理的对照组和低浓度(70 mM)NaCl、Na2CO3、Na2SO4溶液处理的土壤,土壤含水量急剧下降,同时冬小麦叶片相对含水量也相应的急剧下降;而用较高盐浓度处理的土壤和冬小麦叶片含水量降低较慢。在干旱胁迫过程中,对照组冬小麦在短时间（6 d）内干旱叶片便出现萎蔫,并伴随着丙二醛、脯氨酸含量、SOD等抗氧化酶活力急剧增加并一直高于盐处理的冬小麦。相反高浓度盐处理的冬小麦在干旱处理12 d时叶片直立生长良好,叶片MDA、抗氧化酶活力均增加,但增加幅度均低于对照。脯氨酸含量随干旱胁迫增加,但随盐处理浓度增加而上升幅度减小。在复水处理5 d后,叶片含水量均增加,MDA和脯氨酸含量下降,但抗氧化酶活力仍增高。荒漠环境土壤中盐离子一方面可提高土壤和植物的保水率,提高水分利用率,另一方面激活体内的抗氧化酶系统使植物较早获得抗逆能力,这可能是荒漠植物多抗逆性形成的部分生理生化原因。 相似文献
8.
Comparative Study of the Impact of Drought Stress on P.centrasiaticum at the Seedling Stage in Tibet
Pennisetum centrasiaticum is widely distributed in arid and semi-arid areas of Tibet. Its rhizome system is developed and has strong resistance to adversity. In this study, the physiological characteristics and drought resistance of P.centrasiaticum seedlings from 12 drought-stressed sites in Tibet were examined at the Lhasa Plateau Ecosystem Research Station of the Chinese Academy of Sciences. PEG-6000 solution with five levels of water potential (0, -0.7, -1.4, -2.1, and -2.8 MPa) was used to simulate drought stress, and malondialdehyde (MDA), proline (Pro) and chlorophyll contents were determined. The balance between production and elimination of reactive oxygen species in P.centrasiaticum was destroyed, leading to membrane lipid peroxidation and the production of MDA, and accelerating the decomposition of chlorophyll. P.centrasiaticum absorbed water from the outside to resist drought by secreting proline and other osmotic regulating substances. The Pro and chlorophyll contents in P.centrasiaticum showed a temporary rising trend, and then decreased with the decrease in water potential. MDA content increased with the decrease in water potential. By using the membership function method, the drought resistance of P.centrasiaticum seedlings from the 12 areas was evaluated, and the results showed that the drought resistance at the sites went from strong to weak in this order: Xietongmen > Linzhou > Sog > Damxung > Tingri > Namling > Gyirong > Linzhi > Purang > Dingjie > Longzi > Sa’gya. The drought resistance of P.centrasiaticum was strong in Xietongmen, Linzhou and Sog. Whether P.centrasiaticum from these three areas is suitable for cultivation in arid and semi-arid areas of Tibet needs further study. 相似文献
9.
研究了土壤含水量和磷肥对马铃薯生长发育及抗旱生理的影响,结果显示：（1）土壤含水量的下降导致马铃薯幼苗叶片含水量和叶绿素含量降低,可溶性糖、脯氨酸、丙二醛（MDA）含量、相对电导率（REC）及超氧阴离子（O2-·）产生速率升高,抗氧化酶活性增强,株高、茎粗、根长、匍匐茎数、地上部分干重降低,马铃薯块茎重量及块茎淀粉、蛋白质、Vc含量下降;（2）不同水分条件下增施适量磷肥,显著提高了马铃薯叶片含水量、叶绿素含量,相对增强了抗氧化酶活性,降低了相对电导率、MDA含量和活性氧水平,且马铃薯块茎重量及块茎淀粉、蛋白质和Vc含量显著增加。（3）比较包括对照在内的6种磷肥增施量,增施15.3 g·m-2磷肥对马铃薯幼苗抗旱性及生长发育的促进效果最佳。综上所述,干旱胁迫显著抑制了马铃薯幼苗生长发育,而增施适量磷肥可通过提高渗透调节物质含量和抗氧化酶活性,有效缓解干旱胁迫下马铃薯幼苗叶片的脂质过氧化程度及细胞膜损伤,减轻干旱对生长发育的抑制,增强植株整体抗旱性。 相似文献
10.
Shunguo Yan Changgui Wan Ronald E. Sosebee David B. Wester Ernest B. Fish Richard E. Zartman 《Journal of Arid Environments》2000,46(4):397
Responses of photosynthesis (Pn), stomatal conductance (gs), pre-dawn leaf water potential (Ψlp) and leaf water content (ωl) of creosote bush to 10 rainfall events in the Chihuahuan Desert were investigated. Infiltration of rainwater was manipulated by applying municipal biosolids. The responses of Pnand water relation parameters to rainfall (>10 mm) were mainly dependent upon drought severity: (1) following a moderate drought, Pn, gs, Ψlpand ωlrecovered to corresponding values of irrigated plants within 2 days after a 23-mm rainfall; (2) Ψlpand gsresponded to a 15-mm rainfall within 2 days, following a 25-day drought, whereas responses of Pnand ωlwere delayed for several days; (3) responses of Pn, gs, Ψlpand ωlto a 14·7-mm rainfall were all delayed for several weeks following a 110-day drought, but the delay was longer in Pn, gsand ωlthan in Ψlp. Creosote bush responded to small rainfall events (approximately 6 to 8 mm) with an increase in Ψlp, but without noticeable changes in gsand Pn, suggesting a strong stomatal control of water loss even though xylem embolism was reduced. Biosolids applied at high rates (3·4 and 9 kgm−2) decreased the soil water by 2 to 4 mm following rainfall events, and this in turn delayed and decreased the responses of Pnand water relation parameters to rainfall.Pnand gswere linearly related to ωland exponentially related to Ψlp. With the generally coincidental responses of Pnor gsand ωlto rainfall, we concluded that the responses of Pnand gsto rainfall were dependent on leaf rehydration which resulted from restored hydraulic conductance following drought. 相似文献
11.
新疆古尔班通古特沙漠地表具有发育完好的生物土壤结皮,本文以参与组成生物土壤结皮的优势藓类———齿肋赤藓(Syntrichia caninervis)为研究对象,在实验室内对其进行模拟降雨处理,降雨量分别为0mm(对照)、2mm、6mm、10mm和15mm,研究模拟降雨影响下齿肋赤藓植株含水量、光合色素含量及可溶性糖、游离脯氨酸、可溶性蛋白、抗氧化酶(SOD、CAT和POD)、丙二醛含量的变化,以探讨其对降雨的生理生化响应。结果表明:随降雨量的增加,齿肋赤藓植株含水量显著增加;随齿肋赤藓植株含水量的增加,其光合色素含量和可溶性蛋白含量显著增加;随降雨量增加,抗氧化酶(SOD、CAT和POD)活性和可溶性糖含量呈大致递减的趋势,游离脯氨酸和丙二醛含量呈先下降后上升的变化趋势。在干燥状态下齿肋赤藓通过提高体内保护酶(SOD、CAT和POD)活性,增加可溶性糖和游离脯氨酸含量来抵御外界干旱胁迫的环境;而降雨能够增加齿肋赤藓植株含水量,激活其光合生理活性,显著提高光合色素含量,但是降雨量过大又将加剧齿肋赤藓膜脂过氧化的程度。 相似文献
12.
以3个地理种源(武威、张掖、酒泉)蒙古沙拐枣(Calligomum mongolicum)两年生苗木为试材,研究干旱胁迫对其光合及荧光参数的影响,并采用投影寻踪法对其进行了抗旱性评价。结果表明:干旱胁迫导致3个地理种源蒙古沙拐枣光合作用均有所下降,但下降幅度不同,尤其在张掖和酒泉种源间差异显著(p0.05)。在重度干旱时,3个种源的光合速率(Pn)酒泉武威张掖,蒸腾速率(Tr)张掖武威酒泉,气孔导度(Gs)酒泉武威张掖。干旱胁迫下,3个地理种源蒙古沙拐枣的荧光特性表现为初始荧光(Fo)和非光化学淬灭系数(qN)升高,最大光学效率(Fv/Fm)、实际光能转化效率(ФPSⅡ)和光化学淬灭系数(qP)降低。在重度胁迫下,3个种源的Fo和qP大小排序分别为张掖武威酒泉,Fv/Fm、ФPSⅡ和qN为酒泉武威张掖。以投影寻踪法对3个地理种源蒙古沙拐枣的抗旱性排序结果为酒泉武威张掖。 相似文献
13.
The desert plant Hedysarum scoparium uses leaflets and rachises as its photosynthetic organs. The abundance of leaflets was lower under unfavorable environmental conditions and higher with improved water conditions. To examine the characteristics associated with the adaptation of H. scoparium to its environment, we selected plants with both compound leaves and rachis without leaflets to study the anatomical structures and gas exchange characteristics of the two organs. The results show that the water storage tissues in rachises were more developed compared with the leaflets. The diurnal courses of the net photosynthetic rate for the rachis and the leaflet were both in a bimodal pattern. Meanwhile, both two peak values of the rachis were significantly higher than those of the leaflet. The daily average transpiration rate was significantly higher in the rachis than in the leaflet in order to lower the temperature of the rachises. It was concluded that under desert drought conditions, the leaflets of H. scoparium were partially or completely degraded to reduce the transpiration area as an adaptive response to water deficit, and only the rachises were retained as photosynthetic organ. The rachises were found to be better suited to a desert habitat than the leaflets. 相似文献
14.
通过对抗逆性不同的6个烟台冬小麦品种在盐处理和干旱胁迫交互作用进程中叶片相对含水量（RWC）,膜脂过氧化产物（MDA）和抗氧化酶活力（SOD,POD,CAT）及渗透调节物含量（脯氨酸,可溶性蛋白）的分析,以了解不同冬小麦品种对盐处理和干旱胁迫交互作用响应的生理调节差异。研究表明,在水分供应充足条件下盐处理10 d,6个品种冬小麦生长良好并和对照没有差异,但在干旱胁迫中盐处理组较对照MDA含量低,RWC和抗氧化酶活力和渗透调节物含量均高,且叶片萎蔫较对照出现晚。但经盐处理的6个冬小麦品种对干旱胁迫响应有差异。在长期干旱(12 d),抗旱性强的品种RWC（81%）明显高于抗旱性弱的（62%）,前者叶片MDA含量较后者低30%,抗旱性强的品种抗氧化酶活力和渗透调节物含量略低于抗旱性弱的品种,但是差异不明显。在盐处理和干旱胁迫交互作用下,盐离子自身可作为渗透调节物既增加了土壤的持水力又提高了细胞保水力而使冬小麦耐旱性增强。抗旱性强的冬小麦品种对盐处理反应敏感且保水性强,细胞膜脂过氧化程度较低,故耐旱力高,抗旱性弱的品种则相反。研究进一步表明,在未来干旱地区实施适度的盐水灌溉可提高冬小麦的耐旱力,但选择抗旱力强的冬小麦品种是实施这一农业耕作措施的关键。 相似文献
15.
水杨酸对干旱下烤烟幼苗膜质和叶绿素荧光特性的影响 总被引：1，自引：0，他引：1
以烤烟品种龙江911为材料,研究了叶面喷施水杨酸（SA）对干旱胁迫下烤烟幼苗叶绿素含量、叶绿素荧光特性和细胞膜伤害程度的影响。结果表明,干旱胁迫下烤烟幼苗叶片的膜系统受到了伤害,光合作用的原初反应和光能在两个光系统之间的分配发生了改变。叶面喷施0.5 mmol·L-1和1.0 mmol·L-1SA减轻了干旱引起的细胞膜丙二醛的增加,有效地保护了烤烟幼苗叶片的膜系统。同时,0.5 mmol·L-1和1.0 mmol·L-1SA减轻了干旱胁迫下叶绿素的分解,有效缓解干旱对类囊体膜和PSⅡ反应中心的伤害,增强了烤烟幼苗对干旱胁迫的适应能力,其最适宜的浓度为0.5～1.0 mmol·L-1。2.0 mmol·L-1SA对烤烟幼苗有一定的毒害作用。 相似文献
16.
Lablab purpureus(50 cultivars throughout the world) is a drought-tolerant legume widely grown as a high-protein grain food and forage legume within a wide range of neotropical regions with extensive production in India and similar climatic areas of Asia, Africa, Central and South America. The objective of this work was to study the nitrogen-fixing potentialities of L. purpureus under the effects of the extreme environmental conditions prevailing in the southern part of Egypt aiming at the recommendation of its propagation in areas of the National giant projects.L. purpureusinoculated with Rhizobium sp. Strain I4 (21 days after planting) grown on Nile valley and Wadi Allaqi soils was relatively tolerant to mild levels of salinity, but the nodule number was reduced to about 35% of the control plants when subjected to a high salt level (120mM NaCl). Lablab plants were similarly affected by different rates of water deficits. This legume was tolerant to moderate levels of drought. The nodule number and weight at 50% of field capacity was about 70% of the control. These values were reduced to 45–55% at a field capacity of 16·5%.Absolute nitrogenase activity, leghaemoglobin content of nodules and protein content of bacteroids and cytosol were moderately affected by mild levels of NaCl and drought but significantly reduced to about 25–35% of the control treatments.The results also indicate that plants grown on the soil of Nile Valley exhibited slightly higher values (nitrogenase, protein, etc.) than those grown on Wadi Allaqi soil. This would encourage the possibility of propagating L. purpureus in the newly reclaimed areas of southern Egypt. 相似文献
17.
Vegetation, microclimate, seedling frequency, freezing tolerance, and cold acclimation were compared for seedlings of Artemisia tridentata collected from 1775, 2175, and 2575 m elevation in the eastern Sierra Nevada, California. Data were used to test the hypothesis that ecotypic differences in stress physiology are important for seedling survival along gradients from desert to montane ecosystems. The vegetation canopy cover and A. tridentata seedling frequency were greatest at 2575 m, compared to 1775 and 2175 m. Snow cover ameliorated temperatures near the soil surface for part of the winter and depth varied across elevations. Freezing tolerance was compared for seedlings maintained in growth chambers at day/night air temperatures of 25°C/15°C. The temperature at which electrolyte leakage and Photosystem II function (FV/FM) from leaves were half-maximum was approximately −13·5°C for leaves of seedlings from all three elevations. Shifting day/night air temperatures from 25°C/15°C to 15°C/5°C initiated about 1·5° of acclimation by plants from all three altitudes, with seedlings from the highest elevation exhibiting the greatest acclimation change. Measurements of ambient air and canopy temperatures at the three elevations indicated that wintertime average low temperatures were consistent with the measured degree of freezing tolerance. At small spatial scales used in this study, pollen and seed dispersal between study sites may have precluded resolution of ecotypic differences. Patterns of freezing tolerance and cold acclimation may depend on a combination of mesoclimate and microclimate temperatures, canopy cover, snow depth, and snow melt patterns. 相似文献
18.
In the present study, growth and water relation parameters were analysed in drought-stressed Coriaria nepalensis Wall. seedlings. C. nepalensis seedlings were subjected to four drought cycles of 7, 14, 21, and 28-days, and to one control level (watered on alternate days) in a glasshouse. The seedlings failed to survive a 28-days drought during summer. Osmotic adjustment (defined as the decrease in osmotic potential at zero or full turgor in response to water deficit) was measured as the difference between the osmotic potential of seedlings watered on alternate days (control) and those subjected to 21-days drought cycle. Seedlings subjected to 21-days drought had a predawn water potential of −2.60 MPa, and showed an osmotic adjustment of −1.95 MPa at full turgor and −2.17 MPa at zero turgor. The growth of seedlings was positively related to moisture and with water potential. With decline in soil moisture the root:shoot ratio increased while leaf weight ratio decreased. Leaf characteristics, such as leaf number, leaf area, leaf area ratio, specific leaf area and leaf drop, were also affected by moisture stress. This study has indicated that osmotic adjustment is a major adaptive mechanism of C. nepalensis that aids successful regeneration of seedlings in degraded sites with inhospitable soil conditions. 相似文献
19.
Burial of different growth stages of plants （e.g., adult plants, seedlings and seeds） is frequent in dune ecosystems. The soil micro-environment, which differs from surface conditions, influences the survival and growth of dune plants. To sum up knowledge about the survival mechanisms of plants under sand burial and to promote practical rehabilitation of dune vegetation, we reviewed relevant published literature and concluded that： （1） Focus in recent years has been on impacts of sand burial on seed germination and seedling emergence. Generally, shallow burial increased seed germination and seedling emergence, but deeper burial was negative. Buried at the same depth, large seeds showed higher germination and seedling emergence rates, attributed to larger energy reserves. （2） Survival, growth and reproduction rates of dune plants show plasticity in response to sand burial. Long-term deep burial is fatal because it creates a physical barrier which overcomes the vertical growth of plants, reduces photosynthetic leaf area, and limits oxygen availability to roots. Modest burial, on the other hand, is advantageous for growth and reproduction of many dune plants, due to protection from excessive temperature and drought. （3） There are few reports concerning effects of sand burial on plant physiology, but a limited number of studies indicate that partial burial increases water use efficiency, chlorophyll content, transpiration rate and net photosynthetic rates. The antioxidant protective enzyme system and osmolyte balance were reported to be involved in the mechanisms of dune plant resistance to burial. 相似文献
20.
In the field of phylogenetic analyses, the rbcL gene encoded large subunit Ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco, EC4.1.1.39), which plays a crucial role in the process of photosynthesis for most terrestrial plants, has been considered to be conserved; however, recent controversy regarding rbcL conservation has appeared since it was proposed to be under natural selection within all principal lineages of land plants. In this study, by examining the variation of DNA and protein sequences among 17 species in the family Tamaricaceae, three nonsynonymous mutations were identified to be under positive selection. The favored sites were located in the alph-helix domains of Rubisco, with decreased hydrophobicity and increased entropy, which could facilitate CO2 penetration into the active site of Rubisco. We also found that the expression level of rbcL in different genotypes of Reaumuria soongarica shifted in response to various stresses such as drought, temperature, salt, and light. This study not only sheds light on the functional/structural features of Rubisco in the evolution scenarios from C3-like into C4 in Tamaricaceae but also provides useful information on directing genetic performance to enhance photosynthesis efficiency of desert plants for sustaining fragile desert ecosystems; furthermore, it promotes the ability to cope with desert aridification and global warming. 相似文献