Effects of water stress on berberine, jatrorrhizine and palmatine contents in amur corktree seedlings

Amur corktree (Phellodendron amurense) is one of the important associated species in broadleaved-Korean pine forests, and in the pharmaceutical resource plants of famous Chinese traditional medicine, named cortex phellodendri. Berberine, jatrorrhizine and palmatine are the main alkaloids to which high attention is paid by the researchers. In the present study, water stress treatments with four conditions, that is, mild drought, severe drought, waterlogging, and control (soil water potentials were controlled in the ranges of-40—-20 KPa,-80—-60 KPa, <-80 KPa and-20—0 KPa), were performed using the technique of root-sphere osmotic irrigation in a soil pond. The changes in the main medicinal compositions of berberine, jatrorrhizine and palmatine contents under different water conditions were discussed. As for the annual growing of amur corktree seedlings, mild drought was generally beneficial to the synthesis and accumulation of the three above-mentioned alkaloid contents. The three alkaloid contents did not show great changes under severe drought whereas those contents had significantly reduced under waterlogging compared with controls. Meanwhile, the growth of amur corktree seedlings was inhibited by the treatments of drought and waterlogging. The height, diameter and biomass of amur corktree seedlings were significantly lower than those of the control seedlings, which meant that the three alkaloid contents in a single seedling still kept the highest in control seedlings. Stem cortex was the medical part in Chinese traditional medicine and also kept the most abundant of the three alkaloid contents in amur corktree. Results indicated that short periods of mild drought could improve the berberine contents in the stem cortex, which might have reference value for the cultivation of amur corktree seedlings to obtain alkaloids.     

Fluctuation of Vegetative Storage Proteins in the Seedlings of Swietenia macrophylla, Analogous to the Seasonal Changes of Those in the Shoot of the Adult Tree

In order to Identify appropriate plant materials for studying the gene expression and biological function of vegetative storage proteins （VSPs） in woody plants, the VSPs in the seedlings of Swietenla rnacrophylla King were investigated by using light microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis （SDS-PAGE） and Western.blotting. The seed of S. macrophylla was rich in storage proteins that accumulated In the vacuoles of cotyledon parenchyma cells in appearance of compact spherical grains. The growth and development of S. macrophylla seedlings were characterized by an obvious growth rhythm. The storage proteins In seeds disappeared during seedling growth while VSPs appeared in the stem 2 weeks after seedling leaves matured. Thereafter, the VSPs In the seedling stem almost exhausted during new shoot growth, and when the leaves of new shoot Just matured, both the stem beneath the new shoot of seedlings and the stem of new shoot started to accumulate VSPs. Nitrogen application dramatically Increased the level of VSPs, but had little influence on the dynamics of VSP consumption and accumulation in seedling stem. Together with these data, the fluctuation of VSPs in seedlings was very similar to that in the branches of the adult trees. In addition, seedlings are easy to be treated due to their small size. Our results suggested that S. rnacrophylla seedlings were suitable for Investigating the biological roles of VSPs and the mechanism of nitrogen storage in trees.     

EFFECTS OF SOIL MOISTURE CONTENT ON DRY NURSERY SEEDLING QUALITY OF LATE DOUBLE CROPPING RICE IN SOUTH CHINA

In the present paper, an experiment was conducted to study the effects of soil moisture content on dry nursery seedling quality in Guangzhou in 1995. Through comparing the difference of dry nursery seedlings and wet nursery seedlings, we found a close relationship between soil moisture content and seedling growth. The seedling emergence of dry nursery seedling was more even, tidy and faster, and the survival rate was higher than that of wet nursery seedling. Dry nursery seedlings had small plant stature, slow leaf stretching speed and low individual seedling dry weight, but had high dry/fresh weight ratio. This was abeneficial factor for seedlings to recover from transplanting shock more quickly. As com-pared with the wet nursery seedlings, dry nursery seedlings had poor rooting ability,but had more vigorous white roots and fewer rust roots. It was the possibly important reasonfor dry nursery seedlings to form strong“explosive force”.     

Response of transgenic potato seedlings to allelopathic pressure and the effect of nutrients in the culture medium

Chinese farmers frequently use a wheat–potato cropping system. The land area planted to transgenic potatoes is increasing because transgenic potatoes have greater resistance to pests and diseases. However, little is known about the bio-compatibility of transgenic potatoes with wheat straw. The objective of this tissue culture study was to determine the allelopathic effects of wheat straw on transgenic potato seedlings. Seedlings were cultured on normal MS medium (normal treatment) and nutrient-deficient MS medium (acclimated treatment) and then transferred to MS medium, which contained wheat straw powder. Wheat straw powder inhibited potato seedling growth in both treatments. Among the parameters analyzed in this study, inhibition was greatest for plant fresh weight and least for plant height. The inhibitive effects of wheat straw were greater for seedling roots compared to shoots. Resistance to allelopathic pressure from wheat straw was greater in acclimated seedlings compared to normal seedlings. This suggested that previous pressure may have induced tolerance in the transgenic potato seedlings. Furthermore, growth inhibition of potato seedlings from the normal treatment increased as the amount of wheat straw powder in the culture medium increased. Calculations indicated that the presence of wheat straw would lead to a 55% reduction in the total biomass of normal potato seedlings compared to a 39% reduction for acclimated seedlings. Parameters such as net photosynthesis rate (Pn) and quantum yield (Y(II)) changed as the nutrient content of the culture medium increased or decreased, but the changes in the parameters were smaller for acclimated seedlings compared to normal seedlings. This suggests that nutrient status during the culture period could help transgenic potato seedlings adapt and compensate for energy loss from seedlings in defending against allelopathic pressure. In summary, the results show that previous exposure to pressures such as nutrient deficiency may increase the allelopathic pressure resistance of transgenic potato seedlings.     

Response of transgenic potato seedlings to allelopathic pressure and the effect of nutrients in the culture medium

Chinese farmers frequently use a wheat–potato cropping system. The land area planted to transgenic potatoes is increasing because transgenic potatoes have greater resistance to pests and diseases. However, little is known about the bio-compatibility of transgenic potatoes with wheat straw. The objective of this tissue culture study was to determine the allelopathic effects of wheat straw on transgenic potato seedlings. Seedlings were cultured on normal MS medium (normal treatment) and nutrient-deficient MS medium (acclimated treatment) and then transferred to MS medium, which contained wheat straw powder. Wheat straw powder inhibited potato seedling growth in both treatments. Among the parameters analyzed in this study, inhibition was greatest for plant fresh weight and least for plant height. The inhibitive effects of wheat straw were greater for seedling roots compared to shoots. Resistance to allelopathic pressure from wheat straw was greater in acclimated seedlings compared to normal seedlings. This suggested that previous pressure may have induced tolerance in the transgenic potato seedlings. Furthermore, growth inhibition of potato seedlings from the normal treatment increased as the amount of wheat straw powder in the culture medium increased. Calculations indicated that the presence of wheat straw would lead to a 55% reduction in the total biomass of normal potato seedlings compared to a 39% reduction for acclimated seedlings. Parameters such as net photosynthesis rate (Pn) and quantum yield (Y(II)) changed as the nutrient content of the culture medium increased or decreased, but the changes in the parameters were smaller for acclimated seedlings compared to normal seedlings. This suggests that nutrient status during the culture period could help transgenic potato seedlings adapt and compensate for energy loss from seedlings in defending against allelopathic pressure. In summary, the results show that previous exposure to pressures such as nutrient deficiency may increase the allelopathic pressure resistance of transgenic potato seedlings.     

Effects of simulated nitrogen deposition on growth and photosynthesis of 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings

To study the impact of nitrogen deposition on 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings in pots, the dissolved NH₄NO₃ was sprayed on the seedlings every 3 days for 1 year. The simulated elevated N depositions were equivalent to N0(0), N1(6 gN/(m² a)), N2(12 gN/(m² a)), N3(24 gN/(m² a)) and N4(48 gN/(m² a)). The results indicated that medium N treatments (N2, N3) enhanced growth significantly. The height, stem base diameter and per-seedling biomass of Chinese fir seedlings increased with N loads and decreased in the high N treatments. Compared to N0, the height and per-seedling biomass were highest in N2 treatment and increased by 10.77% and 12.35%, respectively. The stem base diameter was highest in N3 treatment and increased by 8.81% compared to N0. The net photosynthetic rate (Pn) in treatments N1, N2, N3, N4 increased by 1.20%, 9.28%, 24.23% and 4.30%, and the highest photosynthetic rate by 67.09%, 125.32%, 148.10% and 51.90%, respectively. The N1–N3 treatments, especially N2, stimulated light compensation point (LCP) of the seedlings significantly, but N4 exhibited inhibitive effect. Compared with LCP, light saturation point (LSP) showed weaker response to N loads, positive to N2, but negative to all other N treatments. Low-to-medium N treatments (N1, N2) enhanced Chl (a + b) by 2.19% and 37.15%, while medium-to-high N treatments (N3, N4) reduced Chl (a + b) by 7.95% and 15.56%, respectively. Water use efficiency (WUE) and stomatal conductance (C) decreased slightly with N loads.     

Effects of simulated nitrogen deposition on growth and photosynthesis of 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings

To study the impact of nitrogen deposition on 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings in pots, the dissolved NH₄NO₃ was sprayed on the seedlings every 3 days for 1 year. The simulated elevated N depositions were equivalent to N0(0), N1(6 gN/(m² a)), N2(12 gN/(m² a)), N3(24 gN/(m² a)) and N4(48 gN/(m² a)). The results indicated that medium N treatments (N2, N3) enhanced growth significantly. The height, stem base diameter and per-seedling biomass of Chinese fir seedlings increased with N loads and decreased in the high N treatments. Compared to N0, the height and per-seedling biomass were highest in N2 treatment and increased by 10.77% and 12.35%, respectively. The stem base diameter was highest in N3 treatment and increased by 8.81% compared to N0. The net photosynthetic rate (Pn) in treatments N1, N2, N3, N4 increased by 1.20%, 9.28%, 24.23% and 4.30%, and the highest photosynthetic rate by 67.09%, 125.32%, 148.10% and 51.90%, respectively. The N1–N3 treatments, especially N2, stimulated light compensation point (LCP) of the seedlings significantly, but N4 exhibited inhibitive effect. Compared with LCP, light saturation point (LSP) showed weaker response to N loads, positive to N2, but negative to all other N treatments. Low-to-medium N treatments (N1, N2) enhanced Chl (a + b) by 2.19% and 37.15%, while medium-to-high N treatments (N3, N4) reduced Chl (a + b) by 7.95% and 15.56%, respectively. Water use efficiency (WUE) and stomatal conductance (C) decreased slightly with N loads.     

Monovalent cation transporters; establishing a link between bioinformatics and physiology

Toxic aluminum (Al) ion is a major constraint to plant growth in acid soils. Aluminum tolerance in wheat (Triticum aestivum L.) is strongly related to the Al-triggered efflux of malate from root apices. A role of the secreted malate has been postulated to be in chelating Al and thus excluding it from root apices (malate hypothesis), but the actual process has yet to be fully elucidated. We measured Al content and root growth during and after Al exposure using seedlings of near-isogenic lines [ET8 (Al tolerant) and ES8 (Al sensitive)] differing in the capacity to induce Al-triggered malate efflux. Aluminum doses that caused 50% root growth inhibition during 24-h exposure to Al in calcium (Ca) solution (0.5 mM CaCl₂, pH 4.5) were 50 μM in ET8 and 5 μM in ES8. Under such conditions, the amount of Al accumulated in root apices was approximately 2-fold higher in ET8 than ES8. Al-treated seedlings were then transferred to the Al-free Ca solution for 24 h. Compared to control roots (no Al pretreatment), root regrowth of Al-treated roots was about 100% in ET8 and about 25% in ES8. The impaired regrowth in ES8 was observed even after 24-h exposure to 2.5 μM Al which had caused only 20% root growth inhibition. The addition of malate (100 μM) during exposure to 50 μM Al in ES8 enhanced root growth 1.6 times and regrowth in Al-free solution 7 times, resulting in similar root growth and regrowth as in ET8. Short-term Al treatments of ES8 for up to 5 h indicated that the Al-caused inhibition of root regrowth started after 1-h exposure to Al. The stimulating effect of malate on root regrowth was observed when malate was present during Al exposure, but not when roots previously exposed to Al were rinsed with malate, although Al accumulation in root apices was similar under these malate treatments. We conclude that the malate secreted from root apices under Al exposure is essential for the apices to commence regrowth in Al-free medium, the trait that is not related to the exclusion of Al from the apices.     

连作土灭菌对葡萄根际土壤微生物群落功能的影响

In order to explore the correlation between soil microbial community function and plant growth, using 30 year continuous cropping soil of grapevines as research object, we studied the effects of sterilization of continuous cropping soil at different temperatures on the growth of grapevines and the microbial community function of rhizosphere soil. The results showed that plant height and stem diameter of grapevines grown in continuous cropping soil were lower than those in the other treatments. With the increasing sterilization temperature, the plant height and stem dia meter of grapevines increased. The ratio of bacteria to fungi in rhizosphere soil increased with the increasing sterilization temperature. The activity of rhizosphere microbes using carbon source was in order of continuous cropping soil sterilized at 100 ℃ > non continuous cropping soil > continuous cropping soil sterilized at 60 ℃ > continuous cropping soil. The regression analysis showed that amino acid (carbon source) in Biolog ECO plate had a significant correlation with microbial metabolic activity of rhizosphere soil. PCA analysis showed that lysine in root exudate had a highest contribution to the variance of principal components in each treatment, and it may play an important role in the obstacle of continuous cropping of grapevines.     

The effect of ecological management in the upper reaches of Heihe River

Heihe River is the second largest inland river in northwest China which flows through Qinghai Province, Gansu Province and Inner Mongolia Autonomous Region. Because of the rapid development of social economy, the sharp increase of water utilization in the middle reaches and the aggravation of contradiction of supply and demand on water resources, the water to the lower reaches decreases and the ecological environment deteriorates constantly. According to the severe situation of ecology system depravation in Heihe River basin, Chinese government decided to invest 2.35 billion RMB to carry out 3 years ecological management in Heihe River basin from August in 2001. After 3 years ecological management, the depravation of ecological environment is controlled effectively. This paper researches the ecological management engineering in the upper reaches of Heihe River and evaluates the effect of the ecological management engineering. The methods of field sampling and measuring are used to obtain the index indicating the ecology change in the upper reaches of Heihe River in 2006. The effects of fencing grassland, fencing natural forest, and artificial afforestation to the ecology are evaluated. The result suggests that: Firstly, in fencing grassland area, the yield of grass had increased by 42–113%, average height of the grass had increased by 60–100%, and the degree of coverage had increased by 67–100%. Secondly, in fencing natural forests area, the degree of coverage had increased by 15–33%, the shade density had increased by 50–100%, average height had increased by 80–125%, and the crown size had increased by 63–186%. Thirdly, the growth increment of the trees in artificial afforestation area is bigger than that outside artificial afforestation area. In conclusion, ecological management leads to obvious ecological effect in the upper reaches of Heihe River.     

涝渍胁迫对不同树种生长和能量代谢酶活性的影响

为了解涝渍条件下不同树种的耐涝性和适应性,通过田间模拟试验,分析了涝渍胁迫对1年生落羽杉、美国山核桃和乌桕实生苗生长及能量代谢酶的影响.试验分为对照、渍水和淹水3个处理,处理时间为60 d.结果表明：在渍水和淹水条件下,3种树种的相对生长率均表现为落羽杉>美国山核桃>乌桕,落羽杉耐涝性最强,乌桕耐涝性最弱.涝渍条件下,3种树种的根冠比显著增加,更多的光合产物被分配到根系.3树种乙醇脱氢酶和乳酸脱氢酶活性显著升高,其中耐涝性强的落羽杉增加幅度不大,但一直维持在较高水平;而乌桕和美国山核桃在处理初期增幅较大,在处理后期呈下降趋势.3种树种的苹果酸脱氢酶、磷酸己糖异构酶和葡萄糖-6-磷酸脱氢酶-6-磷酸葡萄糖酸脱氢酶的活性均低于对照,其中落羽杉降幅最低,淹水条件下分别下降35.6%、21.0%和22.7%.耐涝性强的树种能够通过自身的调节,维持各种能量代谢途径的强度,为树种在低氧条件下的生命活动提供能量,进而维持一定的生长量.     

供氮水平对爬山虎幼苗生长形态和氮分配的影响

通过水培试验,研究了不同氮素水平(0、0.15、0.3、0.45、0.6和0.75g.L-1)条件下爬山虎幼苗的生长形态和体内氮分配状况.结果表明:低氮处理的爬山虎侧枝发育较小,而较高氮处理的侧枝着生位置低,且长度显著高于低氮处理;供氮水平的提高能促进植株的生物量及茎、叶、根氮含量和氮累积量的增加,其中叶生物量占全株生物量的比例最高,在50%以上;叶的氮累积量占整个植株总氮量的60%～70%.     

涝渍对3个树种生长、组织孔隙度和渗漏氧的影响

为了了解落羽杉(Taxodium distichum)、乌桕(Sapium sebiferum)和美国山核桃(Carya illinoensis)等树种的耐涝机制, 采用盆栽模拟涝渍环境的试验方法, 设置了淹水、渍水和对照3个处理, 测定了一年生落羽杉、乌桕和美国山核桃实生苗的生长、组织孔隙度、根氧消耗等指标。结果表明, 涝渍处理抑制了落羽杉、乌桕和美国山核桃的生物量和生物量增量(渍水处理下落羽杉的生长得到了促进), 增加了3树种的根冠比, 从生物量和生物量增量下降幅度来评价, 落羽杉的耐涝性最强, 其次为美国山核桃。淹水和渍水处理下, 落羽杉、乌桕和美国山核桃的根、茎和叶中的组织孔隙度显著增加, 且随着处理时间的延长, 各器官的组织孔隙度有增加的趋势, 3个树种中, 落羽杉的根、茎和叶中的组织孔隙度均较其他2个树种高。淹水和渍水处理下, 移除茎明显增加了落羽杉、美国山核桃和乌桕的根的氧消耗, 表明涝渍处理增强了O₂在3个树种体内的运输并通过根系扩散到涝渍土壤中的能力, 并且随着处理时间的延长, 3个树种体内运输O₂并扩散到土壤中的能力有逐渐增强的趋势。因此, 涝渍环境总体上抑制了落羽杉、乌桕和美国山核桃等树种的生长, 但各树种为了适应这种生长环境, 形成了大量的通气组织, 从而导致各器官组织孔隙度的增加, 增强了O₂通过植物体运输到根系并扩散到土壤中的能力, 解决了根系及根际缺氧的矛盾。     

Effect of an Epichloë endophyte on adaptability to water stress in Festuca sinensis

As water stress, including drought and waterlogging, can severely affect plant growth, this study investigated the effects of an endophyte from the genus Epichloë on two different ecotypes of Festuca sinensis grass under five soil water conditions in a controlled greenhouse experiment. Changes in F. sinensis plants grown with (E+) and without the endophyte (E−) were evaluated as they were subjected to different water treatments (20%, 35%, 50%, 65% and 80% relative saturation moisture content, RSMC). Growth parameters such as plant height, number of tillers, blade width, stem diameter, root length, total biomass, root-shoot ratio and relative water content were determined. The results showed that drought and waterlogging significantly (P < 0.05) inhibited the growth of F. sinensis. The presence of the endophyte significantly (P < 0.05) increased plant growth and root-shoot ratio under drought and waterlogged conditions. In addition, the plant height, number of tillers, blade width, stem diameter and total biomass in seedlings of both ecotypes reached the maximum at 65% RSMC, which suggests the optimal water condition. These findings also show that moderate drought (35% and 50% RSMC) could promote root growth of grass seedlings. Therefore, endophytic infections can result in enhanced host plant resistance to drought and waterlogged conditions.     

Leaf and stem anatomical responses to periodical waterlogging in simulated tidal floods in mangrove Avicennia marina seedlings

This study was aimed to evaluate anatomical responses to waterlogging of mangrove seedlings (Avicennia marina (Forsk.) Vierh.) grown in experimentally simulated semidiurnal tides. The following treatments were used: 0, 2, 4, 6, 8, 10 and 12 h submergence period with two daily tidal cycles. With increasing waterlogging duration, the leaf thickness, mesophyll thickness, palisade parenchyma thickness, palisade–spongy ratio and hypodermis thickness decreased, but the mesophyll to leaf thickness ratio, stem and pith diameter, and cortex thickness increased. The tangential vessel diameter, vessel wall thickness in stem and leaf and fiber wall thickness in stem showed a similar tendency in response to waterlogging, remaining constant between 0 and 4 h waterlogging duration, but decreasing with more prolonged waterlogging. When the waterlogging duration exceeded 4 h, no sclerenchyma cells in leaves or gelatinous fibers in stems were observed. The response of these leaf and stem features indicated that water transport and mechanical support could remain relatively stable in the 0–4 h waterlogging duration, but they would be negatively influenced by longer flooding. Tissues for gas exchange were stimulated by waterlogging, while the functions of water storage, photosynthesis, mesophyll conductance were weakened with increasing waterlogging.     

不同灌水量对2个蓝浆果品种幼苗生长和耗水规律的影响及相关性分析

以兔眼蓝浆果(Vaccinium ashei Reade)品种'Brightwell'和南方高丛蓝浆果(V.corymbosum hybrids)品种'Misty'为研究对象,研究不同灌水量〔50%WC、75%WC、100%WC(CK)和125%WC〕(WC为单株日耗水量)对幼苗生长、单株耗水量的日变化和月变化、单株净增干质量、总耗水量和水分利用效率的影响,并采用回归分析法对单株月耗水量与月均温和月均空气相对湿度的相关性进行分析.结果显示:随灌水量提高,2个品种幼苗的地径、单株枝长和单株总叶面积的增量总体上均不断增大,但单株枝长增量略有波动;单株根、茎、叶和总干质量总体上均逐渐增大,根冠比则逐渐减小;单株净增干质量和总耗水量均随灌水量提高而增大,而水分利用效率则在50%WC条件下最低、在75%WC条件下最高.在相同灌水量条件下,品种'Misty'幼苗的地径和单株枝长的增量,单株茎、叶和总干质量及水分利用效率基本上均高于品种'Brightwell',而其单株总叶面积增量、单株根干质量、根冠比和总耗水量却基本上低于后者.在7月份至9月份,2个品种幼苗单株耗水量的日变化基本上呈单峰曲线,但其单株耗水量峰值出现的时间段则因品种和灌水量不同而异;在全天不同时间段和不同月份,2个品种幼苗的单株耗水量均随灌水量提高而增大;在相同灌水量条件下,品种'Misty'幼苗的单株耗水量总体上低于品种'Brightwell'.回归分析结果表明:2个品种幼苗的单株月耗水量与月均温呈显著或极显著正相关,与月均空气相对湿度呈显著或极显著负相关.综合分析结果表明:蓝浆果幼苗的耗水量不但与品种特性有关,而且还受到土壤水分含量、气温和空气湿度的影响;在相同灌水量条件下,品种'Brightwell'幼苗的耗水量高于品种'Misty',但其水分利用效率却低于后者.在中国南方地区,品种'Brightwell'和'Misty'的适宜灌水量分别为100%WC和75%WC.     

五叶爬山虎实生苗的生长特征对水分梯度下保水剂的反应

为探讨保水剂和未来降雨变化对五叶爬山虎实生苗生长特征的影响及寻求改善生态环境的途径,在内蒙古正蓝旗育草站开展了爬山虎实生苗生长特征对水分梯度下保水剂的反应的实验。结果表明:保水剂处理更能显著提高土壤的有效含水量,并能保持较长时间;爬山虎幼苗的株长、侧枝数、叶数及茎、叶、根和植株生物量增重等指标均随施水的增多而增大,但保水剂处理增幅较大,尤其是W3和W4两种供水与对照相比均达显著水平;保水剂处理还影响植株的生物量分配,尤其对叶重比和根重比影响显著,而茎重比和根冠比两种处理差异较小。     

Growth,abscisic acid content,and carbon isotope composition in wheat cultivars grown under different soil moisture

Changes in dry matter accumulation and allocation, abscisic acid content and carbon isotope composition of three wheat cultivars from dry, middle and wet climate regions were recorded at full maturity after exposure to different watering regimes (100, 50 and 25 % field capacity). Compared with the wet climate cultivar, the dry climate cultivar showed lower stem height, total leaf area, total dry biomass and total grain dry mass, and higher root/shoot ratio, abscisic acid content and carbon isotope composition under all watering regimes. Both water-limited treatments significantly reduced leaf growth and increased dry matter allocation into the roots leading to a significant raise of root/shoot ratio in all cultivars tested. In addition, drought affected morphological and physiological properties more in the dry climate cultivar than in the wet climate cultivar.     

盐胁迫对裸果木幼苗生长和叶片相关生理指标的影响

裸果木起源于古地中海,为亚洲中部荒漠区分布的第三纪孑遗植物种,对研究旱生植物演化过程具有重要的科学价值。以一年生裸果木(Gymnocarpos przewalskii)实生苗为材料,在盆栽条件下用质量浓度为0.4%、0.8%、1.2%和1.6%的NaCl溶液进行盐胁迫处理,测定各NaCl处理下裸果木幼苗叶片的抗氧化酶活性、渗透调节物质含量、叶绿素含量、相对电导率(REC)、丙二醛(MDA)含量以及株高、基径,根、茎、叶、总干重,根冠比变化,探讨裸果木幼苗对盐胁迫的生理耐受性。结果显示,(1)随着盐胁迫程度的加重,裸果木幼苗株高、基径,以及根、茎、叶干重和总干重整体呈下降趋势,而根冠比呈上升趋势;裸果木幼苗株高、基径和根干重在0.4%NaCl处理下较对照变化不显著,但其茎干重、叶干重和总干重在各NaCl处理下均显著低于对照。(2)随着盐胁迫程度的加重,裸果木幼苗叶片的可溶性糖(SS)含量、可溶性蛋白(SP)含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性均先升高后降低,而脯氨酸(Pro)含量、过氧化氢酶(CAT)活性、REC、MDA含量均呈持续升高趋势;在0.8%NaCl处理...     

Importance of adventitious roots to growth of floodedPlatanus occidentalis seedlings

Summary Flooding of soil with standing water for 50 or 110 days drastically reduced growth of 178-day-oldPlatanus occidentalis seedlings, with growth inhibited more as the duration of flooding was increased. Flooding reduced the rate of height and diameter growth, leaf initiation and expansion, and dry weight increment and relative growth rates of leaves, stems, and roots. Flooding also induced leaf epinasty, leaf necrosis, and formation of hypertrophied lenticels and many adventitious roots on submerged portions of stems. Severing of adventitious roots after 50 and 95 days from the submerged portions of stems of continuously flooded seedlings reduced several growth parameters including height and stem diameter growth and relative growth rates of leaves and roots. Evidence for the physiological importance of flood induced adventitious roots is discussed.Research supported by College of Agricultural and Life Sciences, University of Wisconsin, Madison and by Yamagata University, Tsuruoka, Japan. The technical assistance of John Shanklin is appreciated.