Comparative Studies on Water Relations and Xeromorphic Structures of Some Plant Species in the Middle Part of the Desert Zone in China

The mean value of leaf water potential (LWP) of the mesophytes, the less-succulent xerophytes and the succulent xerephytes was –13.5, –18.09 and –26.09 bars respectively. The bound water content (BWC), and the ratio of bound water content to free water content (B/E ratio) for the succulent xerophytes (174.0% and 4.8) were higher than those for the mesophytes (52.5% and 0.37) and the less-succulent xerophytes (76.8% and 1.0). The transpiration rate of the mesophytes, less-succulent xerophytes and succulent xerophytes was 1146.5, 866.3 and 422.8 mg/g. fw. h respectively. The water holding capacity (WHC) of the succulent xerophytes was the strongest among those of the three types, while that of the mesophytes was the weakest. The xerophytes, both the succulent and the less-succulent, have the following xeromorphic structures: thick cuticle, sundan stomata, dense epidermal hairs, well-developed palisade tissue and degenerated spongy tissue, the high ratio of palisade tissue to spongy tissue, and equilateral leaves. Besides, succulent xerophytes possess other xeromorphic structures: thick leaves, well-developed water storing tissue, high ratio of water tissue to leaf thickness, and the succulent leaves. The mesophytes exhibit the following mesophilous structures, thin cuticle, levelling or arching up stomata, low ratio of palisade tissue to spongy tissue, and back-belly leaves.     

不同生态型的喜旱莲子草对莲草直胸跳甲化蛹能力的影响

 喜旱莲子草(Alternanthera philoxeroides)是一种水陆两栖的外来杂草,我国1986年从美国引进了该草的专食性天敌莲草直胸跳甲(Agasicles hygrophila)进行生物防治。该天敌的化蛹能力受喜旱莲子草不同生态型的影响,从而影响到其生物防治的效果。从形态解剖的角度结合天敌和寄主植物的田间生理生态学研究了其机理。结果表明：水生型喜旱莲子草无次生结构,而陆生型则具紧密的次生结构和丰富的晶体;不同生态型的喜旱莲子草茎秆形态和结构特征有显著差异,同一生态型草不同位置结构特征也存在显著差异。主成分分析和聚类分析结果表明当λ=3.56时,不同生态型不同节间位置可分为3类,这3类正好可解释田间喜旱莲子草受控制的情况。相关分析表明莲草直胸跳甲的化蛹率与茎秆节间长、茎秆外直径、髓腔成简单正相关,与皮层薄壁细胞厚度和密度、维管束厚度及髓腔薄壁细胞的厚度成简单负相关;用逐步回归建立了化蛹率与形态和解剖结构特性的模型（y=1.533　2-0.248　3x3-0.051　2x4-1.634　9x5-0.957　7x6R2=0.999　9）,表明茎秆直径大小不是影响莲草直胸跳甲化蛹能力的最重要因子,主要原因为维管柱的厚度,其次髓部薄壁细胞厚度、皮层密度和皮层厚度也不同程度影响了莲草直胸跳甲的化蛹能力。从解剖学角度解释了莲草直胸跳甲对不同生态型喜旱莲子草控制作用的机理：对水生型喜旱莲子草有良好控制效果,而对陆生的中间型能起到一定抑制作用,对陆生的旱生型基本无控制作用。     

我国荒漠不同生态类型植物的旱生结构

本文研究了我国荒漠15种不同类型植物的解剖结构。结果表明,超旱生和旱生植物具有典型的旱生结构,尤以超旱生植物明显,例如沙冬青、梭梭。 旱生结构的基本特征是：叶片及角质层厚,具表皮毛、腺毛、瘤状或乳状突起,气孔下陷,栅栏组织及贮水组织发达,构成等面叶及肉质叶,具含晶细胞和粘液细胞;维管束鞘、维管束帽及纤维细胞的存在,增强了植株的坚固性。中生植物叶片及角质层较薄：气孔平置或拱起,栅栏组织及海绵组织同等发育,胞间隙大,为背腹叶,这是典型的中生结构。     

Comparative Studies on Relationships Between Proline Accumulation and Photosynthesis,Respiration and Chlorophyll Content of Some Plant Species in the Middle Part of the Desert Zone in China

The proline content of mesophytes, less-succulent xerophytes and succulent xerophytes were 0.42, 1.73 and 7.22 mg／g·dw·h respectively. The latter is 17 and 4 times both of the formers. The proline content of xerophytes-both succulent and less-succulent, under non-irrigation condition was higher than that under irrigation condition. The photosynthetic rates of less-succulent and succulent xerophytes were 16.74 and 14.04 CO2 mg／g·dw·h respectively, without clear difference between them. The photosynthetic rate of mesophyte (37.57 CO2 mg／g·dw·h) was more than 2 times that of two types of xerophytes. The respiratory rate of less-succulent xerophytes, succulent xerophytes and mesophytes were 6.27, 4.73 and 7.60 CO2 mg／g·dw·h respectively. The ratios of photosynthetic rate to respiratory rate in less-succulent xerophytes, succulent xerophytes and mesophytes were 2.50, 3.09 and 4.59 CO2 mg／g·dw·h respectively. This fact indicated that the carbon assimilatory process of mesophyte was evidently higher than the respiratory process for all the two types of plants. There was no obvious difference between the total contents of chlorophyll in the three types of plants.     

A Preliminary Study of Xeromorphism of Some Important Xerophytes Growing in Tungeli Desert

In the present paper, using photo-microscopic method, the xeromorphism of some important xerophytes growing in south-east edge of Tungeli desert were determined. The xerophytes appeared to be different from mesophytes at common characteristics, lower in ratio between superficial area and mesophyll tissue volume and higher in ratio between palisade tissue and parenehyma. The xerophytes may be divided into two major groups; selerophylous xerophytes are characterized by a lot of small stomata, a large number of epidermal hair and developed conducting tissue and succulent xerophytes are characterized by a few of big stomata, thickness cuticle and developed water storage tissue. The role of xeromorphism in drought-resistance was also discussed.     

内蒙古锡林河流域植物功能群组成及其水分利用效率的变化--依水分生态类群划分

依照植物水分生态类群,将锡林河流域主要植物种划分为6个植物功能群:呈生植物、中旱生植物、旱中生植物、中生植物、湿中生植物和湿生植物.沿土壤水分梯度,我们调查了8个植物群落的功能群组成及其δ13C值.结果表明:1)在水分状况不同的8个群落中,植物功能群的组成有很大差异.在较湿润生境中(沼泽化草甸和盐化草甸),湿中生和湿生植物成为优势种并构成地上生物量的主要部分;在干旱生境中(草甸草原、典型草原和退化草原),旱生和中旱生植物占绝对优势并构成群落生物量的90%以上;2)不同功能群δ13C值表现为:旱生植物(26.38‰)=中旱生植物(26.51‰)＞旱中生植物(-27.02‰)＞中生植物(-27.56‰)=湿中生和湿生植物(-27.80‰),表明随着不同水分生态类群所适应生境从干旱到湿润逐渐转变,植物的水分利用效率显著降低;3)在土壤水分状况不同的生境下,旱生植物始终维持相对较高的δ13C值和水分利用效率;而中旱生植物的δ13C值表现出较大的变化幅度,表明其对土壤水分的改变更敏感;4)旱生植物叶片脯氨酸含量最高;旱中生、中旱生和中生植物次之;湿中生和湿生植物脯氨酸含量最低.不同水分生态类群脯氨酸含量与其δ13C值和地上生物量呈显著正相关关系.     

内蒙古锡林河流域植物功能群组成及其水分利用效率的变化——依水分生态类群划分

依照植物水分生态类群,将锡林河流域主要植物种划分为6个植物功能群:旱生植物、中旱生植物、旱中生植物、中生植物、湿中生植物和湿生植物。沿土壤水分梯度,我们调查了8个植物群落的功能群组成及其d13C值。结果表明:1)在水分状况不同的8个群落中,植物功能群的组成有很大差异。在较湿润生境中(沼泽化草甸和盐化草甸),湿中生和湿生植物成为优势种并构成地上生物量的主要部分;在干旱生境中(草甸草原、典型草原和退化草原),旱生和中旱生植物占绝对优势并构成群落生物量的90%以上;2)不同功能群d13C值表现为:旱生植物(-26.38) = 中旱生植物(-26.51) > 旱中生植物(-27.02) > 中生植物(-27.56) = 湿中生和湿生植物(-27.80),表明随着不同水分生态类群所适应生境从干旱到湿润逐渐转变,植物的水分利用效率显著降低;3)在土壤水分状况不同的生境下,旱生植物始终维持相对较高的d13C值和水分利用效率;而中旱生植物的d13C值表现出较大的变化幅度,表明其对土壤水分的改变更敏感;4)旱生植物叶片脯氨酸含量最高;旱中生、中旱生和中生植物次之;湿中生和湿生植物脯氨酸含量最低。不同水分生态类群脯氨酸含量与其d13C值和地上生物量呈显著正相关关系。     

Correlation between changes in photosynthetic activity and changes in total protoplast volume in leaf tissue from hygro-, meso- and xerophytes under osmotic stress

Rates of photosynthesis of leaf slices from various hygro-, meso- and xerophytes were measured in the absence of stomatal control in various stages of osmotic dehydration. The external osmotic potential _° for a 50% inhibition of photosynthesis varied between 20 bar in some hygrophytes up to 50 bar in xerophytes. The response of photosynthetic enzymes to increased salt concentrations in the reaction medium was similar in leaf extracts from hygro-, meso- and xerophytes. The total protoplast volume in vacuum-infiltrated leaf discs from various plants was measured as the difference between ³H₂O-labeled space and [¹⁴C]sorbitol-labeled space. In all plants, the protoplast volume could be reduced to about 55% of the maximum volume of tissue in equilibrium with water, without decreasing photosynthesis. Reduction of the maximal protoplast volume below 55% decreased photosynthesis in all tissues to the same decreased photosynthesis in all tissues to the same degree. At 20% maximal volume, photosynthesis of all plants was completely inhibited. The differential decrease of protoplast volumes of various leaf tissues in response to changes in _° was mainly due to the different osmotic potential of the cell sap (_cs). The relative contribution of sugars to the overall osmolarity of the cell sap was up to nineteen times higher in xerophytes than in hygrophytes. Short-term recovery of photosynthesis after hypertonic stress was good in xerophytes, incomplete in mesophytes and absent in hygrophytes. There was also a large discrepancy between the partial recovery of protoplast volumes and the complete absence of a recovery of photosynthesis in hygrophytes.     

寒区不同海拔橘黄罂粟叶片结构特征的比较研究

橘黄罂粟(Papaver croceum Ldb.)采自乌鲁木齐河源区海拔3600m、2500m两种海拔高度,采用PEG和Epon-812两次包埋方法．在光学显微镜和扫描电子显微镜下叶片剖面结构进行了观察。结果显示：橘黄罂粟叶片既具有中生植物又兼有旱生和湿生植物的部分结构特征,其叶片厚度、表皮细胞外壁角质层表面、外角质层蜡质分泌物的有无、表皮细胞形状、气孔密度、气孔大小、维管束形态组成、CTR值、叶肉细胞叶绿体含量等性状特征,在不同生境的橘黄罂粟间呈现出明显差异;而表皮毛状附属器等性状则差异较小。数值分析叶结构各类性状以及不同性状状态的组合．显示出橘黄罂粟个体形态的多样性与生境的海拔高度相关,并以形态结构上的变化来适应寒区高山环境。     

旱生植物驼绒藜茎的异常次生结构及其发育

藜科旱生植物驼绒藜(Ceratoides latens)成长茎由木栓组织、异常形成层、不规则排列的异常维管束及其间的木质化厚壁结合组织和中央正常的维管柱所组成。木栓组织很发达。异常形成层连成环状。异常维管束外韧型。结合组织细胞紧密围绕在各个异常维管束之间。正常的次生维管柱由数个扇形维管束组成,位于维管束内的束中形成层已失去分生能力。中央的髓细胞大多破毁。在茎的发育过程中,初生生长和早期的次生生长都是正常的。而以后的次生生长由初生韧皮部外方保留的原形成层细胞发生的异常形成层活动所代替。起初,异常形成层仅向内交替产生结合组织细胞和异常维管束,而后来同时还向外分化木栓细胞。这种异常的次生结构对旱生植物具有重要的生态学意义。     

骆驼蓬营养器官的旱生结构

 骆驼蓬是生长在荒漠或盐碱地区的旱生植物,具有显著的旱生结构特征。主根粗壮,其中柱周围产生2或3轮呈同心环状排列的异常维管束。这种异常结构对旱生植物具有重要的生态学意义。茎肉质,其皮层、韧皮部,尤其是髓内具有发达的贮水薄壁组织细胞。叶片肉质,光滑无毛。其表皮细胞的外切向壁有较厚的角质层,表面具皱纹状突起。气孔器与表皮细胞平齐,面积较大,而密度较小。栅栏组织发达,为环栅型,包围着发达的贮水组织。叶脉维管束不发达。其叶表面积与体积之比远比中生植物小。根据以上营养器官形态结构特征,可以认为骆驼蓬是典型的多浆汁旱生植物。     

Development of successive cambia and pattern of secondary growth in the stem of the Neotropical liana Rhynchosia phaseoloides (SW.) DC. (Fabaceae)

The occurrence of flattened stems in Rhynchosia phaseoloides (SW.) DC. (Fabaceae) has been known for years, but little interest has been shown toward elucidating its secondary growth. This study aims to (1) understand the pattern of secondary growth and development of vascular elements from the cambium at different stages of stem growth and (2) elucidate the type, size and distribution of cells related to these processes at different regions of the stem. Dilatation growth in main stems and branches of R. phaseoloides is achieved by successive cambia formed in two areas of the actual cortex that are opposed to each other by approximately 180°. Only the first cambial ring is functionally normal and closed-elliptical in outline, supporting the growth of the middle part of the rather flat stem. Later on, this stem becomes oval to oblong in cross-section outline by the activity of successive cambia from which cells produce further xylem, phloem and parenchyma tissues in a somewhat fan-shaped way. As shown in cross section, a flat cable-like structure of several modules results, forming wings relative to the primary central axis tissues. The secondary cambia are formed by dedifferentiation of cortical parenchyma cells, resulting in small clusters of radially arranged meristematic bands of cells. From these meristematic bands, an outward-facing crescent-shaped new band of cambium is originated. The innermost cells of this meristematic band form the parenchymatic tissue that connects the new lateral module to the proximal one. This occurs several times during the whole stem ontogeny.     

Anatomical Observation of Assimilating Branches of Nine Xerophytes in Gansu

The nine xerophytes grown in Gansu, i.e. Haloxylon persicum Bge., H. ammodendron Bge., Calligonum junceum Litw., C. arborescens Litw., C. leucocladum Bge., C. mongolicum Turcz., C. caput-medusae Schrenk, Hedysarum scoparium Fisch. et Mey. and Limonium aureum Hill., all, especially Haloxylon persicum, possessed distinct structural features of xeromorphism. Generally their leaves were extremely degenerated or exist as basal leaves. Photosynthesis was carried out by the young green twigs. The epidermis of which had thickened cell walls and were overlaid with thick cuticle. Underneath the epidermis it was the hypodermis. Inner to the hypodermis, the well developed palisade layer was shown to have cells containing abundant chloroplasts. Water-storing tissues with large cells were seen central to the palisade tissue. In tran- sverse section, the ratio of the cortex width and stem diameter was greater than that of mesophytes. In contrast, the ratio of cortex width and root diameter was smaller. Crystal cells or mucilage cells probably of xeromorphic charateristics were generally present in these xerophyes.     

大兴安岭兴安落叶松(Larix gmelinii)天然林分级木转换特征

通过调查样地,作树干解析,分析了不同结构兴安落叶松天然林分级木（优势木、平均木和被压木）转换特征。研究表明：（1）不同结构的兴安落叶松天然林分级木转换年龄、方向和转换率均不同。兴安落叶松分级木转换率29.4%。分级木中,优势木、平均木和被压木转换率分别35.3%、41.2%、11.8%。分级木转换中,优势木与平均木相互转换比例较高,优势木转平均木占83.3%,平均木转优势木占85.7%;优势木向被压木转换比例仅为16.7%;被压木不能转换成优势木,只能转换成平均木,被压木中无转换占88.2%,在森林经营和抚育采伐中应考虑伐除这些被压木。（2）在林分年龄36～65a范围内,随着林分年龄增大,其转换率呈增加趋势。林分年龄30～39a、50～59a和60～69a时,其转换率分别0、33.3%和46.7%。（3）随着林分密度增加,分级木转换率呈增高趋势。当林分密度小于2500株.hm^-2时,主要于优势木与平均木间转换。当林分密度大于2500株.hm^-2时,才出现其它分级木与被压木相互转换现象。（4）不同林型分级木转换率和转换方向不同。草类-落叶松和杜香-落叶松林分级木转换率分别50%和9.5%。（5）不同水平格局林分分级木转换率不同。聚集分布和随机分布时,其转换率分别61.1%和13.3%。     

Anatomical and histological factors affecting the ruminal degradation of stem tissues in Bothriochloa species

Anatomical and histological features affecting the degradation of stem tissues by ruminal microorganisms were examined in ‘Caucasian’, ‘Ganada,’ and ‘WW-Spar’ Old World bluestem grasses (Bothriochloa spp.). Tissue degradation and/or staining results revealed variation among cultivars in the degree of lignification of parenchyma, sclerenchyma, and epidermal cells. In both immature and mature stems, parenchyma and sclerenchyma cell degradation by microorganisms was rapid and extensive for Ganada as compared with Caucasian and WW-Spar. In general, Caucasian tissues were more resistant to degradation than WW-Spar. There also were differences in tissue composition and degradation as a result of stem maturity. Increased lignification in parenchyma cells was primarily responsible for a decreased rate and extent of degradation in older stem portions. The major difference in tissue composition among cultivars was found in older stems; WW-Spar had more vascular and less parenchyma tissues than Caucasian and Ganada. However, Caucasian had a greater percentage of xylem-metaxylem complex tissues than the other two cultivars. The amount of lignified tissues did not seem to be related strongly with rate and extent of tissue degradation. Instead, the data suggest that our previously reported differences in digestibility among the three Old World bluestem grasses could be attributed to differences in the degradation of their individual tissue types. Fungal attachment was greatest on mature tissues, hence, the rate and extent of degradation of lignified tissues may be associated with the colonization of fungi in mature stems. Also, there was minimal colonization of fungi on immature tissues suggesting that their degradation was primarily affected by enzymatic or direct involvement of bacteria.     

辽河口湿地植物多样性及物种功能型空间分布格局

辽河口湿地是我国典型的滨海湿地, 在过去几十年受人为过度干扰, 植被变化明显。本研究拟通过野外实地调查揭示辽河口湿地植物多样性及功能型的空间格局。结果表明, 潮上带的物种丰富度和Shannon-Wiener指数均高于潮间带。与潮上带相比, 潮间带的盐生植物与湿生植物比例较高, 而中性植物、甜土植物、中生植物与旱生植物的比例较低。物种丰富度、Shannon-Wiener指数以及中性植物、甜土植物、中生植物、旱生植物的比例均随着与海岸线距离的增加而增加, 盐生植物、湿生植物比例则与之相反。对所调查样地与植物物种的主成分分析(PCA)表明, 潮上带主要为芦苇(Phragmites australis)、刺儿菜(Cirsium setosum)、山莴苣(Lagedium sibiricum)等中性和甜土植物, 潮间带为盐地碱蓬(Suaeda salsa)、扁秆藨草(Scirpus planiculmis)、水烛(Typha angustifolia)等盐生植物。可见, 盐度与水位是决定辽河口湿地植物多样性及物种功能型的关键生态因子。     

Diversity of sequences and expression patterns among alleles of a sugarcane loading stem gene

Modern sugarcane cultivars are highly polyploid and aneuploid hybrids, which are propagated as clones. Their complex genome structure comprises 100–130 chromosomes and 10–13 hom(e)ologous copies of most loci. There is preliminary evidence of very high heterozygosity, with implications for genetic improvement approaches ranging from marker-assisted selection to transgenics. Here, we report that sugarcane cultivar Q200 has at least nine alleles at the Loading Stem Gene (ScLSG) locus. Exon–intron structure is identical and the predicted protein products show at least 92 % identity, across sugarcane alleles and the Sorghum homologue Sb07g027880. There is substantial variation in the 5′ UTR and promoter regions including numerous allele-specific nucleotide polymorphisms, insertions and deletions. We developed an allele-specific qRT-PCR method to undertake the first compelling test of allele-specific expression in polyploid sugarcane. Seven alleles distinguished by this method all showed peak expression in the sucrose-loading zone of the stem, but there was apparent variability in expression patterns across other tissues. The ScLSG2 and ScLSG5 alleles appear promising for specificity of expression in stems, relative to leaf, meristem, emerging shoot and root tissues. Within the stem, there was activity in parenchyma, vascular and rind tissues. This expression pattern is of interest in basic research and biotechnology aimed at enhanced sucrose content, engineering value-added products, and manipulation of stem biomass composition.     

陕北黄土高原蒿属植物的分类与分析

陕北黄土高原有蒿属植物30种1变种,居该地产种子植物属中所含种数的首位。所产蒿属植物在不同的植被带中梯度变化明显,替代现象显著。在生态类型上,旱生类型从南向北递增,中生类型从南向北递减。在区系组成上可分为6种分布区类型,即:我国特有分布,3种;温带亚洲分布,14种1变种;北温带及中亚分布各4种;旧世界温带分布,3种;东亚分布的2种。可见陕北黄土高原蒿属植物种类丰富,梯度变化明显,旱化现象显著,地理成分复杂,但以温带亚洲分布类型为主,兼有其它成分,属典型的温带性质。     

生长调节剂DPC和营养物质KH_2PO_4协同作用对棉苗茎解剖结构的调控效应

在自然光照和遮荫的弱光条件下研究了DPC（助壮素）、KH2PO4（磷酸二氧钾）单独和混合浸种对棉苗茎组织解剖结构的影响,结果表明在两种光照条件下,DPC、KH2PO4对棉苗茎的组织结构都有不同程度的影响。其中以DPC＋KH2PO4处理效果优于单独使用,特别是弱光条件下,此效应更明显。DPC＋KH2PO4处理使棉苗茎秆粗壮,茎秆密度（单位茎高度内予物质重）增加．茎中维管组织发育好,维管束数目多,每一维管束中分化的导管数目增多;木质部、韧皮部面积大并且发育较好,因而加强了茎的生理功能;有利于培青壮苗。