Rootstock-mediated changes in xylem ionic and hormonal status are correlated with delayed leaf senescence, and increased leaf area and crop productivity in salinized tomato

Tomato crop productivity under salinity can be improved by grafting cultivars onto salt-tolerant wild relatives, thus mediating the supply of root-derived ionic and hormonal factors that regulate leaf area and senescence. A tomato cultivar was grafted onto rootstocks from a population of recombinant inbred lines (RILs) derived from a Solanum lycopersicum  ×  Solanum cheesmaniae cross and cultivated under moderate salinity (75 m m NaCl). Concentrations of Na⁺, K⁺ and several phytohormones [abscisic acid (ABA); the cytokinins (CKs) zeatin, Z; zeatin riboside, ZR; and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC)] were analysed in leaf xylem sap in graft combinations of contrasting vigour. Scion leaf area correlated with photosystem II (PSII) efficiency ( F _v/ F _m) and determined fruit productivity. Xylem K⁺ (but not Na⁺), K⁺/Na⁺, the active CK Z, the ratio with its storage form Z/ZR and especially the ratio between CKs and ACC (Z/ACC and Z + ZR/ACC) were positively loaded into the first principal component (PC) determining both leaf growth and PSII efficiency. In contrast, the ratio ACC/ABA was negatively correlated with leaf biomass. Although the underlying physiological mechanisms by which rootstocks mediate leaf area or chlorophyll fluorescence (and thus influence tomato salt tolerance) seem complex, a putative potassium–CK interaction involved in regulating both processes merits further attention.     

Relationships between endogenous hormonal content and direct somatic embryogenesis in Prunus persica L. Batsch cotyledons

Cotyledons of peach (Prunus persica L. Batsch cv. ZiseMay^®) were cultured in vitro on medium deprived of plant growth regulators. Two different lines varying in their embryogenic capacity were studied after 90 days in culture media. Endogenous levels of abscisic acid (ABA), indole-3-acetic acid (IAA), trans-zeatin (Z), trans-zeatin riboside (ZR), the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), salicylic acid (SA), and jasmonic acid (JA) were analyzed in embryogenic and non-embryogenic cotyledons. No significant differences were observed in total ABA, IAA, ZR, SA and JA concentrations between the embryogenic and non-embryogenic cotyledons. On the contrary, lower Z and ACC contents, and also a reduced balance between Z and IAA levels were related with the embryogenic capacity of the cotyledons. These results suggest that the difference in somatic embryo formation capacity observed between embryogenic and non-embryogenic cotyledons is related to their endogenous Z contents, and that the endogenous hormonal balance between Z and IAA is an important index defining the embryogenic potential in peach cotyledons.     

光质对设施葡萄叶片衰老与内源激素含量的影响

以设施延迟栽培条件下叶片衰老速度不同的意大利和无核白鸡心2个葡萄品种为试材,分别进行补充红光和蓝光处理,研究不同光质对叶片衰老过程中叶绿素含量、净光合速率和内源激素含量的影响.结果表明: 与未补光对照相比,红光能够显著提高叶片的叶绿素含量和净光合速率,降低了内源赤霉素(GA₃)含量,但明显减缓了脱落酸(ABA)含量的增加和玉米素核苷(ZR)总含量的减少,从而显著提高了(GA₃+ZR)/ABA值,延缓叶片衰老.叶片衰老前期,蓝光处理叶片叶绿素含量、净光合速率和(GA₃+ZR)/ABA值均低于对照,加速了植株的衰老进程;但在叶片衰老后期,蓝光处理叶绿素含量、净光合速率和(GA₃+ZR)/ABA值逐渐高于对照,在一定程度上延缓了叶片衰老.植物内源激素生长素(IAA)则表现出叶片衰老前期促进叶片生长发育、叶片衰老后期加速衰老的双重作用.意大利叶片衰老速度较无核白鸡心慢.在本试验条件下,红光处理效果最好,有效延缓了叶片衰老进程,延长了叶片的生理功能期.     

分析拟南芥叶片在激素促进的衰老中内源激素变化来解析抑制磷脂酶Dα1延缓激素促进衰老的机制

采后衰老进程在很大程度上受到内源和外源激素的影响。抑制拟南芥中磷脂酶Dα1 (phospholipase Dα1, PLDα1)的表达后,使得外源脱落酸（abscisic acid,ABA）和乙烯加速的离体叶片衰老过程在一定程度上得到了缓解。然而,内源激素在这个过程中的作用尚不清楚。本研究对比分析了野生型和PLDα1缺失型两种基因型拟南芥叶片在3种不同人工老化过程中（离体诱导的、外源ABA和乙烯促进的衰老过程）,内源ABA,茉莉酸甲酯（methyl jasmonate,MeJA）、 吲哚乙酸（indole 3 acetic acid,IAA）、玉米素核苷（zeatin riboside,ZR）和赤霉素（gibberellic acid,GA3）的含量变化。这5种激素对3种不同衰老处理方式的响应模式表明了人工老化过程存在着两个不同阶段,并且在衰老早期每种激素的变化模式相同。PLDα1功能缺失使得激素加速的衰老过程得以延缓,这与内源ABA、MeJA、ZR和IAA的含量变化有关,而与GA3的含量变化无关。同时,ZR和IAA的变化模式也说明了这两种激素的变化可能是缺失PLDα1延缓激素加速的衰老过程这一事件的原因而非结果。     

Effect of ambiol and 2-chloroethylphosphonic acid on the content of phytohormones in potato leaves and tubers

The effects of the antioxidant Ambiol and 2-chlorethylphosphonic acid (2-CEPA) on individual concentrations and concentration ratios of phytohormones, photosynthesis and photophosphorylation rates, sucrose and starch content in tubers, and plant productivity were studied in potato (Solanum tuberosum L). Ambiol increased the ratio of indoleacetic acid (IAA) to abscisic acid (ABA), IAA/ABA, and that of zeatin (Z) and zeatin riboside (ZR) to ABA, (Z + ZR)/ABA. These effects were underlain by an increase in the content of auxins and cytokinins and a decrease in ABA. Unlike Ambiol, 2-CEPA increased the level of ABA, the effect being the most pronounced in the tubers. Ambiol increased the rates of photosynthesis and noncyclic photophosphorylation in chloroplasts isolated from potato leaves. The relation of this phenomenon to auxin and cytokinin accumulation, Ambiol- and 2-CEPA-induced changes in the hormonal balance of potato tubers, carbon metabolism, and plant productivity is discussed.     

Effects of cotton rootstock on endogenous cytokinins and abscisic acid in xylem sap and leaves in relation to leaf senescence

Leaf senescence varies greatly among cotton cultivars, possiblydue to their root characteristics, particularly the root-sourcedcytokinins and abscisic acid (ABA). Early-senescence (K1) andlate-senescence (K2) lines, were reciprocally or self-graftedto examine the effects of rootstock on leaf senescence and endogenoushormones in both leaves and xylem sap. The results indicatethat the graft of K1 scion onto K2 rootstock (K1/K2) alleviatedleaf senescence with enhanced photosynthetic (Pn) rate, increasedlevels of chlorophyll (Chl) and total soluble protein (TSP),concurrently with reduced malondialdehyde (MDA) contents inthe fourth leaf on the main-stem. The graft of K2 scion ontoK1 rootstock enhanced leaf senescence with reduced Pn, Chl,and TSP, and increased MDA, compared with their respective self-graftedcontrol plants (K1/K1 and K2/K2). Reciprocally grafted plantsdiffered significantly from their self-grafted control plantsin levels of zeatin and its riboside (Z+ZR), isopentenyl andits adenine (iP+iPA), and ABA, but not in those of dihydrozeatinand its riboside (DHZ+DHZR) in leaves in late season, whichwas consistent with variations in leaf senescence between reciprocallyand self-grafted plants. The results suggest that leaf senescenceis closely associated with reduced accumulation of Z+ZR, andiP+iPA rather than DHZ+DHZR, or enhanced ABA in leaves of cotton.Genotypic variation in leaf senescence may result from the differencein root characteristics, particularly in Z+ZR, iP+iPA, and ABAwhich are regulated by the root system directly or indirectly. Key words: Abscisic acid, cotton, cytokinins, grafting, leaf senescence Received 23 October 2007; Revised 17 January 2008 Accepted 23 January 2008     

Dynamic Changes of Endogenous Phytohormones During the Development of Embryos Derived from Wheat Crossed with Zea mays and Tripsacum dactyloides

The embryos derived from intergeneric crosses between Triticum aestivum L. (2n = 6x= 42) and Zea mays L. (2n= 20), Tripsacum dactyloides L. (2n= 4x= 72), as results of the elimination of paternal chromosome and having no endosperm as normal, are difficult to develop completely in vivo. Hormonal analyses in such intergeneric hybridized ovaries have been carried out including indole-3-acetic acid (IAA), zeatin (Z) and zeatin riboside (ZR), and abscisic acid (ABA) during different developmental stages of embryo. The results indicated that IAA level in hybridized ovaries was much lower than that in self-pollinated ovaries. Moreover, the active changes of Z+ZR and ABA contents were also different between the above two types of ovary. Nevertheless, the ratio changes of IAA/(Z+ZR) and IAA/ABA were similar between the two types of ovary, the same was true in the ratio changs of IAA, Z+ZR, and ABA to the sum of these three types of endogenous hormones. But the three types of ratios in hybridized ovaries were varied far more greater than those in self-pollinated ones. It suggested the importance to maintain dynamic equilibrium of multiple hormones and sequential regulation during the embryo development. That the distantly hybridized embryos failed to mature successfully was probably associated with a deviation from the normal changes of endogenous hormones levels and balance system of multiple hormones in addition to the lack of endosperm nourishment.     

分析拟南芥叶片在激素促进的衰老中内源激素变化来解析抑制磷脂酶Dα1延缓激素促进衰老的机制

采后衰老进程在很大程度上受到内源和外源激素的影响。抑制拟南芥中磷脂酶Dα1（phospholipaseDtxl,PLDod）的表达后,使得外源脱落酸（abscisic acid,ABA）和乙烯加速的离体叶片衰老过程在一定程度上得到了缓解。然而,内源激素在这个过程中的作用尚不清楚。本研究对比分析了野生型和PLDα1缺失型两种基因型拟南芥叶片在3种不同人工老化过程中（离体诱导的、外源ABA和乙烯促进的衰老过程）,内源ABA,茉莉酸甲酯（methyl jasmonate,MeJA）、吲哚乙酸（indole-3-acetic acid,IAA）、玉米素核苷（zeatin riboside,ZR）和赤霉素（gibberellic acid,GA,）的含量变化。这5种激素对3种不同衰老处理方式的响应模式表明了人工老化过程存在着两个不同阶段,并且在衰老早期每种激素的变化模式相同。PLDα1功能缺失使得激素加速的衰老过程得以延缓,这与内源ABA、MeJA、ZR和IAA的含量变化有关。而与GA、的含量变化无关。同时,ZR和IAA的变化模式也说明了这两种激素的变化可能是缺失PLDα1延缓激素加速的衰老过程这一事件的原因而非结果。     

源库关系改变对棉叶内源激素的影响

以中棉18号为材料,在大田条件下研究了摘蕾引起源库关系改变对主要源叶（对应的主茎叶和对位果枝叶）中内源激素的影响。结果表明;去蕾处理推迟了相应主茎叶和果枝叶中吲哚乙酸（IAA）峰出现,降低了玉米素及其核苷（Z ZR）含量,推迟了果枝叶中异戊烯基腺嘌呤及其核苷（iP iPA)的积累,提前了二氢玉米素及其核苷（DHZ DHZR）的积累,降低了脱落酸（ABA）含量。去除一个蕾对相应叶片内源激素的影响是短期的,随整株源库关系的协调,与对照趋同。激素的这种变化与叶片功能变化是一致的,表明棉花源库关系的协调不仅是物质上的关系,植物激素可能是其中重要的信息调控系统。     

Effects of Ambiol and 2-Chlorethylphosphonic Acid on the Content of Phytohormones in Potato Leaves and Tubers

The effects of the antioxidant Ambiol and 2-chlorethylphosphonic acid (2-CEPA) on individual concentrations and concentration ratios of phytohormones, photosynthesis and photophosphorylation rates, sucrose and starch content in tubers, and plant productivity were studied in potato (Solanum tuberosum L). Ambiol increased the ratio of indoleacetic acid (IAA) to abscisic acid (ABA), IAA/ABA, and that of zeatin (Z) and zeatin riboside (ZR) to ABA, (Z + ZR)/ABA. These effects were underlain by an increase in the content of auxins and cytokinins and a decrease in ABA. Unlike Ambiol, 2-CEPA increased the level of ABA, the effect being the most pronounced in the tubers. Ambiol increased the rates of photosynthesis and noncyclic photophosphorylation in chloroplasts isolated from potato leaves. The relation of this phenomenon to auxin and cytokinin accumulation, as well as Ambiol- and 2-CEPA-induced changes in the hormonal balance of potato tubers, carbon metabolism, and plant productivity, is discussed.     

南方红豆杉种子综合处理过程中内源激素的动态变化

为揭示南方红豆杉种子内源激素与休眠的关系,采用酶联免疫吸附法(ELISA)测定了经过层积处理的种皮和胚乳的脱落酸(ABA)、赤霉素(GA3 )、吲哚乙酸(IAA)、玉米素核苷(ZR)4种内源激素含量的变化情况.结果表明:种子胚乳中内源ABA的含量随着层积时间的延长而逐渐下降,GA含量增加,IAA和ZR的含量先增加后降低...     

磷脂酶Dδ对拟南芥叶片衰老过程中内源ROS和激素含量的影响

活性氧（ROS）和植物激素是植物衰老过程中重要的内在或者外在的调控因子。我们发现,相对于离体诱导的衰老过程,在脱落酸（ABA）和乙烯（ethylene）促进的衰老过程中有较多的活性氧积累;在对拟南芥磷脂酶Dδ（PLDδ）缺失型突变体的研究中发现,与野生型相比,突变体在衰老过程中产生较少的活性氧。我们比较了上述两种基因型的离体叶片在离体、ABA和ethylene三种衰老处理下内源的ABA、茉莉酸甲酯（MeJA）、玉米素核苷（Zeatin Riboside, ZR）和吲哚乙酸（IAA）的含量变化,发现每一种激素对上述三种衰老处理的响应模式都很相似。在离体诱导的衰老中,两种基因型拟南芥的内源激素含量没有差异;而在ABA促进的衰老过程中,PLDδ缺失型突变体叶片中的MeJA的含量较低,ZR和IAA含量较高;在乙烯促进的衰老过程中,突变体中的ABA和MeJA的含量较低,ZR和IAA含量较高。上述内源激素的这种变化可能有助于延缓突变体的衰老。     

The Relationship between Polyamines and Hormones in the Regulation of Wheat Grain Filling

The grain weight of wheat is strongly influenced by filling. Polyamines (PA) are involved in regulating plant growth. However, the effects of PA on wheat grain filling and its mechanism of action are unclear. The objective of the present study was to investigate the relationship between PAs and hormones in the regulation of wheat grain filling. Three PAs, spermidine (Spd), spermine (Spm), and putrescine (Put), were exogenously applied, and the grain filling characteristics and changes in endogenous PA and hormones, i.e., indole-3-acetic acid (IAA), zeatin (Z) + zeatin riboside (ZR), abscisic acid (ABA), ethylene (ETH) and gibberellin 1+4 (GAs), were quantified during wheat grain filling. Exogenous applications of Spd and Spm significantly increased the grain filling rate and weight, but exogenous Put had no significant effects on these measures. Exogenous Spd and Spm significantly increased the endogenous Spd, Spm, Z+ZR, ABA, and IAA contents and significantly decreased ETH evolution in grains. The endogenous Spd, Spm and Z+ZR contents were positively and significantly correlated with the grain filling rate and weight of wheat, and the endogenous ETH evolution was negatively and significantly correlated with the wheat grain filling rate and weight. Based upon these results, we concluded that PAs were involved in the balance of hormones that regulated the grain filling of wheat.     

小麦与玉米及鸭茅状摩擦禾杂交后胚发育过程中内源激素的动态变化

小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）与玉米（Ｚｅａ ｍ ａｙｓＬ．）及鸭茅状摩擦禾（Ｔｒｉｐｓａｃｕｍ ｄａｃｔｙｌｏｉｄｅｓ Ｌ．）杂交后,由于胚乳组织不能正常形成,从而导致胚很难在母本小麦植株上发育至成熟。通过对杂交后的胚不同发育时期的子房内源ＩＡＡ、玉米素（Ｚ）及玉米素核苷（ＺＲ）和ＡＢＡ 的ＥＬＩＳＡ 分析,发现远缘杂交后的胚发育过程中子房内源ＩＡＡ 的浓度明显低于正常发育的子房;而且Ｚ＋ ＺＲ 和ＡＢＡ 的含量的动态变化也和正常自交发育的子房不同,然而ＩＡＡ／（Ｚ＋ ＺＲ）和ＩＡＡ／ＡＢＡ 的比率变化在远缘杂交与正常自交的子房之间有某些相似趋势。ＩＡＡ、Ｚ＋ ＺＲ和ＡＢＡ 与这３ 种激素之和的比率变化在上述两类子房中也有相似之处。可以推断,植物胚胎的正常发育需要多种激素的动态平衡及某一时期某一激素的主导性作用。远缘杂交后的胚之所以不能够顺利发育至成熟,除了缺乏胚乳组织的营养保护之外,或许也和其内源激素的水平及多激素平衡体系偏离常规动态变化有关联     

Principal component analysis of hormone profiling data suggests an important role for cytokinins in regulating leaf growth and senescence of salinized tomato

High throughput analytical methods allow phytohormonal profiling, but the magnitude of the data generated makes it difficult to draw firm conclusions about the physiological roles of different compounds. Principal component analysis (PCA) was used as a mathematical tool to evaluate relationships between physiological and hormonal variables in two experiments with salinised tomato. When tomato plants (cv Boludo F1) were grafted onto a recombinant inbred line (RIL) population derived from a Solanum lycopersicum x S. cheesmaniae cross and grown under moderate salinity (75 mM NaCl) for 100 days under greenhouse conditions, PCA revealed an important role for leaf xylem cytokinins (CKs) in controlling leaf growth and photosystem II efficiency (Fv/Fm) and thus crop productivity under salinity. PCA analysis from a similar experiment, with ungrafted tomato grown under highly saline (100 mM NaCl) conditions, that evaluated the temporal sequence of leaf growth (as relative growth rate, LRGR) and senescence and hormone concentrations, revealed a similar influence of CKs on both processes, since Fv/Fm and LRGR were strongly loaded along the two principal components and placed in the same cluster as leaf trans-zeatin and/or related to other CK-related parameters. The conservative behaviour of the eigen vectors for Fv/Fm and the analyzed phytohormones in different compartments (xylem, leaf and root) between different experiments suggests an important role for CKs in regulating leaf senescence, while CKs and other hormones seem to regulate leaf growth under salinity.Key words: cytokinins, leaf growth, principal component analysis, salinity, senescence, tomatoAn important paradigm of plant growth regulation is that plant roots can sense their environment, alter their metabolism and transmit chemical signals via the xylem to the shoots to regulate shoot physiology.¹ Much work has aimed to substantiate this “chemical signaling hypothesis” by determining the production and distribution of various signals such as the plant hormones ABA, cytokinins, the ethylene precursor ACC and various nutrient ions.² Although this work has largely been “ABA-centric”, in part due to its relative ease of measurement, the advent of high-throughput, multi-analyte physicochemical techniques to quantify plant hormones^3,4 greatly amplifies the information available from analyses of long-distance signaling, and allows us to move away from a priori assumptions as to which hormone(s) might be physiologically relevant to particular processes. Ultimately, interpreting this information is necessary to provide a sound physiological basis to underpin efforts aimed at manipulating long-distance signaling in planta.Full spectrum hormone profiling can potentially assay more variables per sample than the typical number of samples assayed. Principal component analysis (PCA) is a mathematical algorithm that reduces the dimensionality of the data set while retaining most of the inherent variation.⁵ This is achieved by identifying directions, called principal components, along which the variation in the data is maximal. By using few components, each sample can be represented by relatively few numbers instead of values for many variables.⁶ PCA identifies new variables, the principal components, which are linear combinations of the original variables, and may be an appropriate technique to aid understanding of hormone profiling experiments.Recently, we grew a commercial tomato cultivar (cv Boludo F1) grafted onto 100 rootstocks from a population of recombinant inbred lines derived from a Solanum lycopersicum x S. cheesmaniae cross, and exposed the plants to moderate (75 mM NaCl) salinity for 100 days.⁷ The rootstock generated considerable variability in vegetative vigour (assessed as fresh weight of a fully expanded leaf, LFW) and leaf senescence (assessed by the chlorophyll fluorescence parameter Fv/Fm in that leaf). Ionic and hormonal factor(s) putatively regulating these processes (xylem concentrations of Na⁺ and K⁺ and ABA; the cytokinins trans-zeatin, Z, and the storage form trans-zeatin riboside, ZR; and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, ACC) were analyzed in leaf xylem sap collected 50 days after salinisation in seven graft combinations of contrasting vigour. Since different xylem parameters showed a high degree of autocorrelation, PCA was performed in order to gain further insights about their real contribution to the physiological processes. Xylem K⁺, K⁺/Na⁺, the active cytokinins Z and ZR, its sum (Z + ZR) and ratio (Z/ZR), and especially the ratio between cytokinins and ACC (Z (ZR)/ACC and Z + ZR/ACC) were strong and positively loaded into the first principal component (PC1) determining both LFW and Fv/Fm (Fig. 1A⁷). Although other variables are included in the same cluster at the 95% of confidence level, their strength in PC1 was much weaker (e.g., Na⁺, Z/ABA, ACC). Does this PCA output provide generic information about the hormonal processes regulating leaf growth and Fv/Fm of salinized plants, or is it specific to the particular methodological conditions (duration of salinization, choice of genotypes or plant compartment) imposed by our experimental design?Open in a separate windowFigure 1Two axes of a principal components (PC1, PC2) analysis showing plant productivity trait vectors (leaf fresh weight, LFW or relative growth rate, LRGR, and Fv/Fm, indicated by arrows) and the position of various hormonal and ionic variables (denoted by abbreviations) for the long-term grafting experiment which analysed xylem variables (A), and the medium-term experiments with ungrafted plants that analyzed leaf (B) and root (C) variables. Arrows indicate eigen vectors representing the strength (given by the length of the vector) and direction of the trait correlation relative to the first two principal components (PC1, PC2). The circles enclose those variables that fall into the same cluster (95% confidence level). Abbreviations for the variables are given thus: ABA, abscisic acid; AC , 1-aminocyclopropane-1-carboxylic acid; IAA , indole-3-acetic acid; Z, trans-zeatin; ZR, trans-zeatin riboside.To answer this question, PCA was performed on data obtained from a similar experiment where a single genotype of tomato (cv Moneymaker) was exposed to high (100 mM NaCl) salinity for 22 days under hydroponic conditions in a controlled environment chamber.^8,9 Although the same ionic and hormonal variables (including the auxin indole-3-acetic acid, IAA) were assayed in both roots and leaves, xylem ion concentrations were not quantified. Therefore PCA was conducted using leaf relative growth rate (LRGR) as an indicator of vegetative vigour (due to the temporal variation of leaf fresh weight in young plants) and senescence (Fv/Fm), and hormonal and ionic variables measured in leaves (Fig. 1B) and roots (Fig. 1C).Both physiological variables (LRGR and Fv/Fm) were significantly loaded into the two major principal components (PC1 and PC2) explaining more than 90% of the variance, and in which most of the leaf and root ionic and hormonal parameters were strongly associated in three clusters (enclosed within the circles, Fig. 1B and C). As in the PCA from the grafting experiment (Fig. 1A), LRGR and Fv/Fm, were also placed in the same cluster as the cytokinin Z and the ionic variables K⁺ and K⁺/Na⁺ in the leaf (Fig. 1B), although some dissociation between them was observed, probably due to the temporal dynamics of these variables in the same plant organ. Moreover, most of the other CK-related variables (ZR, Z + ZR, Z + ZR/ACC, Z + ZR/ABA) were associated in a distinct cluster that was also strongly loaded along with Fv/Fm parameter in PC1 (Fig. 1B). When the root data were considered (Fig. 1C), all these CK-related (with the exception of Z) and ionic variables were placed in the same cluster as Fv/Fm and loaded into PC1 explaining 71% of variance.Interestingly, the position and value of the eigen vector defining Fv/Fm remained highly conservative and positively associated with hormonal (ZR, Z + ZR, Z + ZR/ACC) and ionic (K⁺, K⁺/Na⁺) variables independent of the experimental design and organ analyzed. However, the position of the vector for LRGR was more variable since its relationship with PC2 and some hormonal parameters (e.g., IAA, IAA/Z + ZR) was positive in the leaves and negative in the roots. Particular attention should be paid to leaf Z concentration since it was highly related to both Fv/Fm and leaf growth vectors in both experiments (Fig. 1A and B), while this hormone was placed in an opposite (to Fv/Fm) or orthogonal (to LRGR) vector in the roots (Fig. 1C). Only two of the hormones analyzed showed differential responses to salinity in leaves and roots suggesting an important role in biomass partitioning: Z and IAA decreased in leaves and increased in roots.⁸ Similar responses of both roots and leaves (for the other hormones) may indicate the importance of root-to-shoot signaling in maintaining hormone homeostasis in particular organs and integrating the whole plant response to the stress, but reciprocal grafting experiments with hormone-content or -sensitivity mutants are required to test this hypothesis for each compound.¹⁰ Additionally, PCA also revealed a conserved position for some hormonal parameters such as ACC and ABA tissue concentrations (Fig. 1B and C) and also the ratio ACC/ABA in both tissues and leaf xylem (Fig. 1A–C), which were always placed in clusters opposed to Fv/Fm (ACC, ABA) and leaf growth (ACC/ABA), supporting a role of these hormones in negatively regulating salt-induced leaf senescence⁹ and growth.⁷The relatively conservative geometric positions of some ionic and hormonal variables, and their co-occurrence with physiological variables of interest, suggest that PCA was relatively insensitive to methodological issues such as duration of salinisation, choice of genotypes or plant compartment. Moreover, similar PCAs for both tissue (Fig. 1B and C) and xylem (Fig. 1A) samples indicate the adequacy of the latter (with its considerably decreased sample preparation time) to infer physiological relationships. Particularly noteworthy was the clustering of cytokinin-related variables with the chlorophyll fluorescence parameter Fv/Fm in both experiments and organs, as well as the leaf Z concentration and growth, which highlighted the potential physiological importance of cytokinins in a way that was not so apparent from inspection of a typical correlation matrix which analyses two variables at a time. Accordingly, we have instigated experiments manipulating the cytokinin status of salinised plants by selectively overexpressing the ipt gene. That these plants grew better, and showed delayed senescence, under salinity (Ghanem ME, unpublished results) supports our use of PCA as a tool to explore temporal^8,9 and genetic⁷ correlations.     

茭白生育过程中地上各部位内源激素的含量变化

以两个茭白品种为试材,测定了植株茎蘖生育过程中地上各部位主要激素及肉质茎膨大过程中的干重变化。结果显示：茭白植株生育过程中各部位的激素以玉米素及玉米素核苷(Z ZR)的含量最高,生长素(IAA)其次,赤霉素(GA3)和脱落酸(ABA)含量很低;在各部位间总体以茎尖最高,叶鞘其次,叶片最低。其中Z ZR含量在肉质茎膨大前即已明显上升,膨大开始后显著下降;IAA含量在肉质茎膨大后期至末期才出现下降;叶片内ABA含量在肉质茎膨大前即开始上升,叶鞘内ABA．含量在肉质茎膨大后期上升,茎尖内则无明显变化;各部位GA2含量在整个生育期内无明显变化。肉质茎的干重增加也与其Z ZR含量下降密切相关。认为Z ZR是刺激肉质茎膨大的关键激素。品种间差异表现为各部位激素含量及其变化有一定差异,尤其是肉质茎膨大阶段差异比较明显。     

大气二氧化碳浓度升高对银杏叶片内源激素的影响

采用开顶箱系统,研究了银杏叶片内源激素脱落酸(ABA)、吲哚乙酸(IAA)、玉米素核苷(ZR)和赤霉素(GA₃)对大气CO₂浓度升高(环境CO₂浓度+350 μmol·mol^-1,EC)的响应.结果表明,EC处理能使ABA含量降低,与对照(CK)相比, ABA含量最大降低63.0%(处理后120 d).EC处理使叶片IAA和ZR含量增加,而且随着处理时间的延长,差异均达显著水平;IAA含量在处理后100 d为CK的2倍,ZR含量在处理后80 d时为CK的2.5倍.EC处理使叶片GA₃峰值提前出现. (IAA+GA₃+ZR)/ABA比值随着银杏的生长逐渐降低,在处理后期(处理后40～120 d)明显高于CK,表明大气CO₂浓度升高可促进银杏的生长发育.     

施氮量对花铃期短期渍水棉花叶片抗氧化酶活性和内源激素含量的影响

于2005-2006年在江苏南京（32°02′ N,118°50′ E）南京农业大学卫岗试验站进行盆栽试验,设置正常灌水和棉花花铃期短期渍水处理（渍水8 d,恢复15 d）,每个水分处理设置3个施氮水平（0、240、480 kg N·hm^-2）,研究施氮量对渍水棉花叶片抗氧化酶活性和内源激素含量的影响.结果表明：在渍水结束时,与正常灌水相比,渍水棉花叶片可溶性蛋白含量、超氧化物歧化酶和过氧化氢酶活性降低,过氧化物酶活性升高,丙二醛（MDA）含量升高;与此同时,内源激素含量发生变化,脱落酸（ABA）含量升高,玉米素核苷（ZR）、赤霉素（GA）、生长素（IAA）含量及ZR/ABA、GA/ABA、IAA/ABA降低;其中以240 kg N·hm^-2渍水棉花MDA和ABA含量最低,而ZR、GA和IAA含量及ZR/ABA、GA/ABA和IAA/ABA最高,净光合速率最高.到停止渍水15 d时,渍水棉花叶片的抗氧化酶活性、MDA含量、内源激素含量与正常灌水处理的差异较小;施氮可提高渍水处理棉花叶片抗氧化酶活性,降低MDA含量,使ABA水平降低,ZR、GA、IAA水平及ZR/ABA、GA/ABA、IAA/ABA升高.本试验中,渍水条件下以240 kg N·hm^-2处理的效果最好,生物量和籽棉产量最高.     

Interactive effects of α-NAA and UV-B radiation on the endogenous hormone contents and growth of Trichosanthes kirilowii Maxim seedlings

The impact of UV-B radiation on endogenous hormones in plants has recently drawn attention from researchers. The mechanism for reduced stem elongation by UV-B might be due to changes in the phytohormone levels, especially IAA, which plays a role in stem elongation. In this study, effects of UV-B radiation on Trichosanthes kirilowii Maxim (T. kirilowii) seedlings in greenhouse-grown plants were investigated. The results indicated that: (1) In comparison to controls, exposure to 0.029 Jm^?2 s^?1. UV-B radiation led to accumulation of endogenous abscisic acid (ABA) and zeatinriboside (ZR) in the plant contents, and decreased contents of endogenous indole-3-acetic acid (IAA) and gibberellic acid (GA_1/3). Exposure to UV-B radiation reduced the height and leaf area of plants. As a result, total biomass (plant dry weight) was lower. (2) In comparison to controls, addition of 2 mg l^?1 α-naphthaleneacetic acid (α-NAA) slightly increased the contents of IAA, GA_1/3 and ZR, and decreased the content of ABA in leaves. This addition of α-NAA significantly increased plant height and leaf area, but only slightly increased total biomass. (3) Addition of α-NAA to UV-B-exposed plants: increased the content of endogenous IAA, GA_1/3 and ZR; decreased accumulation of endogenous ABA; and increased plant height and leaf area in comparison to plants that only were exposed to UV-B. Moreover, total biomass increased slightly. This suggests that addition of α-NAA may compensate to a certain extent for the lack of IAA resulting from UV-B radiation; it also increases the content of GA_1/3 and ZR, decreases the accumulation of ABA, and promotes the growth of plants.     

平阴玫瑰花芽分化期叶片内源激素的变化

对平阴玫瑰花芽分化期叶片甲醇提取物进行IAA、ZR、GA₃、ABA的分离、纯化和测定。结果发现,所测的几种激素均表现出明显的变化规律,其中IAA和GA₃在花芽分化期含量逐渐下降,且在分化临界期出现一低峰,而ZR和ABA则完全相反。同时经比较分析得出ABA/GA₃, ABA/IAA,ZR/GA₃,ZR/IAA也表现明显的变化规律,即比值总体趋势是逐渐提高,且均在分化临界期含量出现一飞跃,显然ABA/GA3,ABA/IAA,ZR/GA₃,ZR/IAA在平阴玫瑰的花芽分化过程中起着重要的调控作用,由此推测,增加植物体内的ABA、ZR的含量或降低IAA、GA₃的含量,都可以促进玫瑰的花芽分化;反之则抑制其花芽分化。