Effects of drought on non-mycorrhizal and mycorrhizal maize: changes in the pools of non-structural carbohydrates, in the activities of invertase and trehalase, and in the pools of amino acids and imino acids

To study the response of non-mycorrhizal and mycorrhizal maize plants to drought, the changes in the pools of non-structural carbohydrates and amino acids were analysed in leaves and roots of two maize cvs. Plants well colonized by the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) (60% of root length infected) and comparable non-mycorrhizal plants were subjected to moderate drought stress by reducing the water supply. This stress induced a conspicuous increase in the trehalose pool in the mycorrhizal roots, probably because it was accumulated by the fungal symbiont. Furthermore, glucose and fructose were accumulated in leaves and roots of non-mycorrhizal plants but not in the mycorrhizal ones. Starch disappeared completely from the leaves of both mycorrhizal and non-mycorrhizal plants in response to drought. Activities of soluble acid invertase and trehalase were also measured. Acid invertase activity increased during drought in the leaves of both non-mycorrhizal and mycorrhizal plants whilst in the roots it was unaffected in non-mycorrhizal plants and decreased in the mycorrhizal ones. Without drought stress, trehalase activity was considerably higher in the leaves and roots of mycorrhizal plants than in those of non-mycorrhizal plants. It increased conspicuously during drought, primarily in the leaves of non-mycorrhizal plants. A drought-induced accumulation of amino acids as well as imino acids was found in roots and leaves of both mycorrhizal and non-mycorrhizal plants; leaves of mycorrhizal plants accumulated more imino acids than those of non-mycorrhizal ones. Our results show that drought stress and the presence of a mycorrhizal fungus have a considerable effect on carbon partitioning, imino acid and amino acid accumulation in maize plants.     

Comparison of Diversity and Functions of Epiphytic Bacteria from Cultivated and Weed Plants in Agrocenoses

Diversity of epiphytic bacterial complexes from cultivated and weed plants was compared according to the frequency of predominance of bacterial taxa in these communities and using the principal component method. The presence of both common dominants on cultivated and weed plants and distinct differences in the composition of the epiphytic bacterial complexes of these plants was revealed. The representatives of chemolithotrophic bacteria capable of tetrathionate and thiosulfate assimilation were found only on weed plants. The antibiotic activity of bacteria isolated from weed plants was almost twice as high as that found for bacteria from cultivated plants. The obtained data indicate the positive effect of bacterial communities of weed plants, which make it possible to protect cultivated plants from phytopathogens.     

Magnesium deficiency results in accumulation of carbohydrates and amino acids in source and sink leaves of spinach

Accumulation of assimilates in source leaves of magnesium‐deficient plants is a well‐known feature. We had wished to determine whether metabolite concentrations in sink leaves and roots are affected by magnesium nutrition. Eight‐week‐old spinach plants were supplied either with a complete nutrient solution (control plants) or with one lacking Mg (deficient plants) for 12 days. Shoot and root fresh weights and dry weights were lower in deficient than in control plants. Mg concentrations in deficient plants were 11% of controls in source leaves, 12% in sink leaves and 26% in roots, respectively. As compared with controls, increases were found in starch and amino acids in source leaves and in sucrose, hexoses, starch and amino acids in sink leaves, whereas they were only slightly enhanced in roots. In phloem sap of magnesium‐deficient and control plants no differences in sucrose and amino acid concentrations were found. To prove that sink leaves were the importing organs they were shaded, which did not alter the response to magnesium deficiency as compared with that without shading. Since in the shaded sink leaves the photosynthetic production of metabolites could be excluded, those carbohydrates and amino acids that accumulated in the sink leaves of the deficient plants must have been imported from the source leaves. It is concluded that in magnesium‐deficient spinach plants the growth of sink leaves and roots was not limited by carbohydrate or amino acid supply. It is proposed that the accumulation of assimilates in the source leaves of Mg‐deficient plants results from a lack of utilization of assimilates in the sink leaves.     

Effects of drought on host and endophyte development in mycorrhizal soybeans in relation to water use and phosphate uptake

Bethlenfalvay, G. J., Brown, M. S., Ames, R. N. and Thomas, R. S. 1988. Effects of drought on host and endophyte development in mycorrhizal soybeans in relation to water use and phosphate uptake. - Physiol. Plant. 72: 565–571.
Soybean [ Glycine max (L.) Merr.] plants were grown in pot cultures and inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe or provided with P fertilizer (non-VAM plants). After an initial growth period (21 days), plants were exposed to cycles of severe, moderate or no drought stress over a subsequent 28-day period by rewatering at soil water potentials of -1.0, -0.3 or -0.05 MPa. Dry weights of VAM plants were greater at severe stress and smaller at no stress than those of non-VAM plants. Phosphorus fertilization was applied to produce VAM and non-VAM plants of the same size at moderate stress. Root and leaf P concentrations were higher in non-VAM plants at all stress levels. All plants were stressed to permanent wilting prior to harvest. VAM plants had lower soil moisture content at harvest than non-VAM plants. Colonization of roots by G. mosseae did not vary with stress, but the biomass and length of the extraradical mycelium was greater in severely stressed than in non-stressed plants. Growth enhancement of VAM plants relative to P-fertilized non-VAM plants under severe stress was attributed to increased uptake of water as well as to more efficient P uptake. The ability of VAM plants to deplete soil water to a greater extent than non-VAM plants suggests lower permanent wilting potentials for the former.     

Accumulation of proline and glycinebetaine in Spartina alterniflora Loisel. in response to NaCl and nitrogen in the marsh

Summary The possible interaction of high soil salinity and low soil nitrogen content in affecting the growth of Spartina alterniflora Loisel in the high and low marshes of the Eastern U.S. was explored. Throughout the whole growing season, the short plants growing in the high marsh, where there was a higher soil salinity and lower available soil nitrogen, contained more proline and glycinebetaine and showed a lower leaf water potential than the tall plants growing in the low marsh. In both short and tall plants, the growing season, with the highest content occurring in spring and fall. In contrast, the glycinebetaine content in both short and tall plants remained fairly constant throughout the growing season, and was consistently at least 10 fold higher than the proline content. It is estimated that 19–30% of the total leaf nitrogen was in the form of proline and glycinebetaine in the short plants, and 14–27% in the tall plants. Ammonium nitrate fertilization in the field resulted in increased growth, higher proline and glycinebetaine contents, and lower water potentials in the short plants, but had little effect on these parameters in the tall plants. We suggest that in the low marsh, the plants can obtain sufficient nitrogen for osmoregulation and other metabolism. In the high marsh with higher soil salinity and lower nitrogen content, the plants have to allocate a even greater proportion of the already limited nitrogen supply for osmoregulation. Thus, nitrogen available for osmoregulation and other nitrogen-requiring metabolism is insufficient, resulting in reduced growth.     

浙江丽水地区珍稀濒危植物区系研究与保护

浙江丽水地区有珍稀濒危植物 42种 ,隶属于 3 7属 2 5科。其中国家二级珍稀濒危植物 1 8种 ,三级珍稀濒危植物 2 4种 ,大致可分划为 1 0个分布类型 5个变型 ,以木本植物占优势 ,中国特有属、单型属较多。本文根据丽水珍稀濒危植物的现状提出了一些具体的保护措施。     

中国天山野果林种子植物组成及资源状况分析

中国天山野果林种子植物共计60科237属435种,种类组成趋向于集中在少数科内,区系优势现象相当明显,反映出野果林自然环境的特殊性与区系的过渡性。在这些植物种类中有国家重点保护植物9种、中国珍稀濒危保护植物3种、自治区重点保护植物9种;林区野生植物资源非常丰富,统计结果表明：野生果树40种、食用植物30种、饲用植物以种、蜜源植物111种、观赏植物132种、香料植物如种、药用植物131种。文中对各类资源植物的特征进行了分析和讨论,并就野果林的保护及可持续利用提出建议。     

云南干热河谷地区种子植物资源与开发利用初探

云南干热河谷植被均为耐旱的旱生植被,主要有以下三种类型：1）半稀树草原（Semi-savanna）型植被;2）肉质多刺灌丛;3）在金沙江上游滇西北的亚热带性的干热河谷地区分布着类似马基(Maquis-like）型的多刺小叶矮生灌丛。按其产物和用途可分为6类：药用植物、纤维植物、树脂和树胶植物、芳香油植物以及淀粉植物等。资源破坏性开发和环境的变化,使现存资源的保护和开发利用成为目前的主要问题。     

Comparison of protein profiles and enzymes in non-mycorrhizal and mycorrhizal roots of Pennisetum pedicellatum

Pennisetum pedicellatum plants were inoculated with Glomus mosseae, G. aggregatum and Gigaspora margarita. There were both quantitative and qualitative changes in the protein pattern of inoculated plants. Gi. margarita induced increase in protein in the plants. Acid phosphatase, alkaline phosphatase, superoxide dismutase and chitinase activities were high at the beginning of infection, but declined as the infection advanced. Gi. margarita was an efficient fungus in enhancing enzyme activity and proteins in roots compared with G. mosseae and G. aggregatum. Protein profile revealed the presence of 12 peaks in mycorrhizal plants compared with 8 in nonmycorrhizal plants.     

浙江瑞安红双林场植物资源及其利用前景

浙江瑞安红双林场共有维管植物167科538属1055种,其中已知有一定利用价值的资源植物715种,隶属于157科429属。按其性质和用途可分为材用植物、药用植物、油脂植物、纤维植物、淀粉植物、食用植物、芳香植物、栲胶植物、保健饮料植物、牧草及饲料植物、保护与改造环境植物、观赏植物、土农药植物、蜜源植物等14类,其中药用植物种类最为丰富。以常见药用植物234种为例,根据植物资源可利用量估量法估量当地植物资源利用前景,结果表明,其中46.2%的常见药用植物可利用量估量值在12以上,可供开发利用。文后提出红双林场植物资源保护与利用建议。     

Genetics and ultrastructure of a cytoplasmically inherited yellow mutant in soybeans

A chimeric plant was observed in the F₂ generation of a cross between a male-sterile line and a plant introduction homozygous for a chromosome interchange in soybeans [Glycine max (L.) Merr.]. F₃ progeny of this plant included one chimera, 36 yellow plants and 16 green plants. The yellow plants, which progressively turn green, were viable and fertile in field, greenhouse and growth-chamber environments. Reciprocal cross-pollinations were made between these yellow plants and four known nuclear yellow mutant plants, between these yellow plants and sibling green plants and between these yellow plants and unrelated green plants. Segregation data from F₁ and F₂ generations indicated cytoplasmic inheritance of the newly discovered yellow phenotype. Pollinations in which reciprocal F₁ hybrid plants were used as male or female parents were made with unrelated green plants. Observations in F₁ and F₂ generations substantiated the hypothesis of cytoplasmic inheritance. No interactions have been observed between this mutant and the various nuclear backgrounds. This is the first report of a cytoplasmically inherited mutant affecting plant color in soybeans. Exchange grafts were made between cytoplasmic yellow plants and sibling green plants and between cytoplasmic yellow plants and unrelated green plants. The phenotype was controlled by the scion, indicating that graft-transmissible agents were not involved. When grown in darkness, cytoplasmic yellow plants and normal green plants accumulated the same amount of protochlorophyllide. Cytoplasmic yellow plants grown in dim light accumulated slightly less chlorophyll than did their green siblings. Electron photomicrographs showed that the prolamellar body (a structure associated with synthesis of protochlorophyllide) and chloroplast ultrastructure were normal in the cytoplasmic yellow mutant. These observations led to the hypothesis that the synchrony involved in deposition of nuclear and cytoplasmic gene products during organelle development is impaired in this cytoplasmic mutant.     

Physiology of Polyploid Plants: Water Balance in Autotetraploid and Diploid Tomato under Low and High Salinity

Diploid and autotetraploid plants of the cultivated tomato Lycopersicon esculentum cv. Lukullus (Luk) were studied under low and high salinity. Polyploids had a higher water content than diploid plants. Water content in both plant types decreased under salinity, the decrease being smaller in the polyploid plants. Dry weight of whole young plants decreased in both diploid and polyploid plants under salinity, the decrease being smaller in the latter. Transpiration of whole plants, grown in control solution, was lower in polyploid than in diploid plants and decreased more under salinity in the latter. Rate of change of water loss of detached drying leaves was similar in diploid and polyploid plants. Leaves of control diploid plants, however, lost more water per unit leaf area during the phase of stomatal closure apparently due to higher stomatal density. Polyploid plants had fewer but more open stomata per unit leaf area, under both control and saline conditions. Root pressure, determined only under control conditions, seemed to be higher in polyploid plants. No difference in Cl^? concentration per unit leaf dry weight was found between diploid and polyploid plants grown in either control or NaCl solution.     

江苏省珍稀濒危保护植物资源及其园林应用前景

珍稀濒危保护植物是人类重要的植物资源之一,江苏地处暖温带和亚热带的过渡地带,自然条件优越,植物种类多样,蕴含着丰富的珍稀濒危保护植物。文章调查整理出78种江苏省珍稀濒危保护植物,隶属40科65属,其中本省自然分布的有21种,从其他省份引种栽培的有57种。为了能促进江苏省珍稀濒危保护植物在园林绿化中的应用,分别从江苏省珍稀濒危保护植物的概况、观赏价值、园林应用现状以及在园林中的应用前景等方面进行论述,以期为绿化工作者提供参考。     

Absorption and translocation of sodium in beans and cotton

At the end of a 4 hour absorption period approximately 95% of the sodium absorbed by bean plants was retained in the secondary roots. The sodium translocated to the shoot was retained in the stem.

2,4-Dinitrophenol decreased the amount retained in the secondary roots of bean plants and increased the amount translocated to the shoot. The stem retained most of the translocated sodium.

Bean plants without roots absorbed considerably more sodium than plants with roots and translocated a greater proportion of the sodium to the petioles and blades. 2,4-Dinitrophenol reduced the amount of sodium in the stem and petioles and increased the amount in the blades.

2,4-Dinitrophenol reduced the amount of sodium retained by the secondary roots of cotton plants but did not appreciably affect the amounts translocated to the shoot.

     

Origins of variance in seed number and mass: interaction of sex expression and herbivory in Lomatium salmoniflorum

Summary As in many plant species, Lomatium salmoniflorum (Umbelliferae) individuals produce many flowers, only a subset of which produce mature seeds that escape seed parasitism and enter the seed bank. The interrelationships between the timing and number of flowers produced, sex expression, seed set, and seed parasitism were studied for their direct and indirect effects on the numbers and masses of viable seeds produced by individual plants. In a sample population of 369 plants that produced 161 386 flowers, 76% of the plants produced some hermaphroditic flowers. The percentage of hermaphroditic flowers increased significantly with the total number of flowers produced by a plant. Seed set was 65–90% in plants producing >600 flowers, but was highly variable in plants producing fewer flowers. Hand-pollinated plants showed the same pattern of seed set, suggesting that variable seed set in small plants may result from insufficient resources for seed development. The majority of schizocarps was produced by only 12% of the plants. Parasites killed 24.5% of the seeds prior to dispersal. Another 14.5% of the seeds lacked endosperm. Hence, the initial 161 386 flowers, which included 25874 hermaphroditic flowers each capable of producing two seeds, produced 42 468 seeds of which an estimated 25906 entered the seed bank as undamaged seeds with fully developed endosperm. Path analysis indicated that the number of hermaphroditic flowers on a plant and the percentage of seeds attacked by seed parasites had the greatest direct effects on the number of viable seeds entering the seed bank. The date at which a plant began flowering and the percentage of flowers setting seed had smaller or only indirect effects on viable seed production. Mean seed mass for plants was not significantly related to any of the factors that affected seed number, but little of the variance in seed mass occurred among plants. Masses of intact seeds in the population ranged 9-fold in both 1987 and 1988. Thirty-five percent of the variance was among seeds within umbels, 46% was among umbels within plants, and only 19% was among plants. The large variation among umbels within plants resulted from a seasonal pattern in which seeds from umbels produced late in the spring had lower mean seed masses than seeds from umbels produced early in the spring. Overall, the results indicate that both direct and indirect interactions between number of flowers, the date of initiation of flowering, seed set, and seed parasitism affect the number of viable seeds entering the seed bank. These interactions strongly bias viable seed output to a small minority of plants that produce many seeds with a wide range of masses over the growing season.     

植物成熟microRNA转录后修饰与降解的研究进展

microRNA(miRNA)是一类长度为20–24 nt的内源小RNA,广泛存在于各种植物体内,参与调控植物器官的形态建成、激素应答、逆境胁迫和营养代谢等一系列过程。虽然miRNA生物合成和功能研究已取得了很大进展,但关于植物成熟miRNA的转录后修饰和降解的研究却报道较少。一方面miRNA如同其它RNA存在半衰期,其降解对于调控细胞内miRNA含量起重要作用,从而调控植物的生长发育或胁迫响应等过程;另一方面,成熟miRNA存在转录后修饰,可影响miRNA的稳定性,最终影响其活性。该文着重从植物成熟miRNA的转录后修饰和降解等方面进行了综述。     

Improvement of vitamin E quality and quantity in tobacco and lettuce by chloroplast genetic engineering

Vitamin E (tocopherol: Toc) is an important lipid-soluble antioxidant synthesized in chloroplasts. Among the 8 isoforms of vitamin E, α-Toc has the highest activity in humans. To generate transgenic plants with enhanced vitamin E activity, we applied a chloroplast transformation technique. Three types of the transplastomic tobacco plants (pTTC, pTTMT and pTTC-TMT) carrying the Toc cyclase (TC) or γ-Toc methyltransferase (γ-TMT) gene and the TC plus γ-TMT genes as an operon in the plastid genome, respectively, were generated. There was a significant increase in total levels of Toc due to an increase in γ-Toc in the pTTC plants. Compared to the wild-type plants, Toc composition was altered in the pTTMT plants. In the pTTC-TMT plants, total Toc levels increased and α-Toc was a major Toc isoform. Furthermore, to use chloroplast transformation to produce α-Toc-rich vegetable, TC-overexpressing transplastomic lettuce plants (pLTC) were generated. Total Toc levels and vitamin E activity increased in the pLTC plants compared with the wild-type lettuce plants. These findings indicated that chloroplast genetic engineering is useful to improve vitamin E quality and quantity in plants.     

中国农业野生植物原生境保护现状及建议

中国的农业野生植物十分丰富,约有1.5万种,从2001年开始实施了农业野生植物原生境保护,目前已建成或正在建设的原生境保护区(点)共20个.然而,由于该项研究起步比较晚,势必存在不足之处,就此提出了相应的建议.     

Origin and evolution of green plants in the light of key evolutionary events

Green plants (Viridiplantae) are ancient photosynthetic organisms that thrive both in aquatic and terrestrial ecosystems, greatly contributing to the changes in global climates and ecosystems. Significant progress has been made toward understanding the origin and evolution of green plants, and plant biologists have arrived at the consensus that green plants first originated in marine deep-water environments and later colonized fresh water and dry land. The origin of green plants, colonization of land by plants and rapid radiation of angiosperms are three key evolutionary events during the long history of green plants. However, the comprehensive understanding of evolutionary features and molecular innovations that enabled green plants to adapt to complex and changeable environments are still limited. Here, we review current knowledge of phylogenetic relationships and divergence times of green plants, and discuss key morphological innovations and distinct drivers in the evolution of green plants. Ultimately, we highlight fundamental questions to advance our understanding of the phenotypic novelty, environmental adaptation, and domestication of green plants.     

The Effect of Single and Repeated Gibberellic Acid Treatment on Internode Number and Length in Dwarf Peas

In long-term experiments comparing the results of single and repeated treatment of dwarf peas with gibberellic acid, both once-treated and weekly-treated plants formed more internodes than control plants. The initial high rate of internode formation in the once-treated peas dropped rapidly reaching that of control plants three weeks after treatment. Weekly-treated plants maintained a higher rate of internode formation. The ratio of internode lengths of once-treated plants to control plants was high (over 3) for the internodes which were elongating during or shortly after the single treatment but dropped rapidly and approached unity in later-developed internodes. The ratio of internode lengths of weekly-treated plants to control plants continued to be high throughout the experiment.