Root Formation on Petioles of Detached Primary Leaves of Dwarf Bean (Phaseolus vulgaris) Pretreated with Gibberellic Acid, Triiodobenzoic Acid, and Cytokinins

Rooting experiments carried out with isolated primary leavesof dwarf bean demonstrated the effect of GA on increasing theIAA level and IAA synthesis. Pretreatment of the lamina of isolatedleaves with GA, especially when tryptophane was added at thesame time, strikingly increased the rooting of petioles. Enhancedroot formation on the petiole of GA-pretreated leaves can beattributed to increase of IAA level by GA in the lamina, i.e.in IAA biosynthesis the utilization of tryptophane releasedfrom the proteins of isolated leaves is promoted by GA. Application of TIBA on the upper part of petiole suppressedthe stimulatory effect of GA on root initiation presumably becauseTIBA inhibits the transport of IAA into the petiole, which resultsin failure of rooting. Pretreatment of the leaves with cytokinins also results in failureof root production. These substances retard protein decompositionin isolated leaves so that the quantity of TPP available forauxin synthesis is less. Simultaneously, this treatment increasesthe cytokinin concentration in the leaf tissues so that theauxin/cytokinin ratio alters and mainly callus forms on thebase of the petioles and differentiation of root primordia cannottake place.     

Correlated evolution of stem and leaf hydraulic traits in Pereskia (Cactaceae)

Recent studies have demonstrated significant correlations between stem and leaf hydraulic properties when comparing across species within ecological communities. This implies that these traits are co-evolving, but there have been few studies addressing plant water relations within an explicitly evolutionary framework. This study tests for correlated evolution among a suite of plant water-use traits and environmental parameters in seven species of Pereskia (Cactaceae), using phylogenetically independent contrasts. There were significant evolutionary correlations between leaf-specific xylem hydraulic conductivity, Huber Value, leaf stomatal pore index, leaf venation density and leaf size, but none of these traits appeared to be correlated with environmental water availability; only two water relations traits - mid-day leaf water potentials and photosynthetic water use efficiency - correlated with estimates of moisture regime. In Pereskia, it appears that many stem and leaf hydraulic properties thought to be critical to whole-plant water use have not evolved in response to habitat shifts in water availability. This may be because of the extremely conservative stomatal behavior and particular rooting strategy demonstrated by all Pereskia species investigated. These results highlight the need for a lineage-based approach to understand the relative roles of functional traits in ecological adaptation.     

Classical and molecular cytogenetics and DNA content in Maihuenia and Pereskia (Cactaceae)

We studied cacti species of the subfamilies Pereskioideae (five species of the southern clade) and both species of Maihuenioideae using molecular cytogenetic techniques and DNA content. Mitotic chromosomes were analyzed for Pereskia aculeata, P. bahiensis, P. grandifolia, P. nemorosa, P. sacharosa, Maihuenia poeppigii, and M. patagonica, using the Feulgen stain, CMA/DAPI fluorescent chromosome banding, fluorescence in situ hybridization (FISH, probes of 5S rDNA and pTa71 for 18-5.8-26S rDNA), and DNA content by flow cytometry technique. The karyotypes were highly symmetrical, most of the pairs being metacentric (m). CMA/DAPI banding revealed the presence of CMA⁺/DAPI^? bands associated with NORs in the first m pair of all species. The co-localization of 18-5.8-26S rDNA loci with CMA⁺/DAPI^?/NORs blocks allowed the identification of homeologous chromosome pairs between species of both subfamilies. FISH using probe 5S rDNA was applied for the first time in both subfamilies. Diploid species had always one m pair carrying 5S rDNA genes, with pericentromeric location in different chromosome pairs. In the tetraploid cytotype of M. patagonica, the 5S rDNA probe hybridized to two pairs. The 2C DNA content obtained by FC varied twofold (from 1.85 to 2.52 pg), with significant differences between species. Mean chromosome length, karyotype formula, percentage of heterochromatin position of 5S rDNA locus, and nuclear Cx DNA content vary among Maihuenia and Pereskia species and allowed to differentiate them. Both genera are closely related and that the differences found are not strong enough to separate Maihuenioideae from Pereskioideae.     

Basal cactus phylogeny: implications of Pereskia (Cactaceae) paraphyly for the transition to the cactus life form

The cacti are well-known desert plants, widely recognized by their specialized growth form and essentially leafless condition. Pereskia, a group of 17 species with regular leaf development and function, is generally viewed as representing the "ancestral cactus," although its placement within Cactaceae has remained uncertain. Here we present a new hypothesis of phylogenetic relationships at the base of the Cactaceae, inferred from DNA sequence data from five gene regions representing all three plant genomes. Our data support a basal split in Cactaceae between a clade of eight Pereskia species, centered around the Caribbean basin, and all other cacti. Two other Pereskia clades, distributed mostly in the southern half of South America, are part of a major clade comprising Maihuenia plus Cactoideae, and Opuntioideae. This result highlights several events in the early evolution of the cacti. First, during the transition to stem-based photosynthesis, the evolution of stem stomata and delayed bark formation preceded the evolution of the stem cortex into a specialized photosynthetic tissue system. Second, the basal split in cacti separates a northern from an initially southern cactus clade, and the major cactus lineages probably originated in southern or west-central South America.     

Endogenous Sugar Levels and Their Effects on Root Formation and Petiole Yellowing of Detached Mustard Cotyledons

Detached cotyledons of Sinapis alba rooted readily in water in petri dishes in the light. The addition of (6 × 10^?2M) galactose, mannose or 2-deoxy-D-glucose to the culture medium proved toxic to cotyledon growth. Of the other sugars tested that were not toxic, sucrose was the most inhibitory to root formation and increased petiolar yellowing to the greatest extent. Glucose was more inhibitory than fructose which in turn increased petiolar yellowing more than methyl-D-glucose. Sucrose, glucose, or fructose at 6 × 10^?2M in the culture medium gave rise to very substantial increases in the cotyledon petiole of reducing sugar and starch with smaller increases in sucrose. Methyl-D-glucose had much less effect on internal sugar levels. It was found that the higher the internal level of glucose the more rapid the rate and final extent of petiolar yellowing. In general, the degree of petiolar yellowing was inversely related to the ability of the cotyledon to root. Methyl-D-glucose differed from the other sugars in that it delayed and reduced root formation but had very little effect on petiolar yellowing.     

光对GA3大麦叶段叶绿素含量的影响

用GA₃处理大麦叶段,在黑暗条件下对叶绿素含量下降无影响,而在光照下有保绿效果。本文就这一现象进行了试验分析,其结果是光的作用在于降低叶内ABA含量,从而减缓叶段内ABA对GA₃的拮抗作用。     

Synergistic Effect of AlCl3 and Kinetin on Chlorophyll and Protein Contents and Photochemical Activities in Detached Wheat Primary Leaves during Dark Incubation

Al³⁺ in combination with kinetin showed more protection against degradation of chlorophyll (Chl) and protein than Al³⁺ or kinetin alone during dark-induced senescence in wheat primary leaf segments. MV-dependent whole chain electron transport, photosystem (PS) 2 mediated oxygen evolution, and PS1 activities were also delayed to a greater extent. Absorbed excitation energy distribution was more in favour of PS1 in Al³⁺ plus kinetin-treated leaf thylakoids at 72 h.     

Paths and Mechanisms of Moisture Movements in Detached Leaves of White Clover(Trifolium repens L.): I. Losses of Petiole Moisture direct from Petioles and via Laminae

The experiments described were concerned with losses of moisturefrom laminae and petioles of leaves of white clover (Trifoliumrepens L.) detached from parent plants, and with the resistancesin the two pathways of loss of petiole moisture-via laminaeand direct from petiole surfaces. Methods involving determination of moisture losses from separatedlaminae and petioles were unsatisfactory and transpiration chamberswere therefore used to permit determinations with intact leaves. Up to 24 per cent of the total petiole moisture was lost viathe laminae, the amount frequently exceeding that initiallyresiding in the xylem of the petioles. Stomatal, cuticular, and external resistances were calculatedat several stages of wilting. Rates of loss of petiole moistureby both pathways were controlled by stomatal and external resistancesin the early stages and by cuticular and internal resistancesin the later stages. Under certain conditions, transpirationof petiole moisture via the lamina ceased earlier than mighthave been expected; estimates were made of the resistances involved.     

Nitrogen Metabolism of Detached Kalanchoe Leaves in the Dark in Relation to Acidification, Deacidification, and Oxygen Uptake

Detached Kalancho leaves were placed in the dark and changesin the amounts of total soluble N, asparagine, glutamine, aminoN, ammonia, and titratable acid were followed during the periodsof acidification and deacidification. Abundant starch was presentthroughout the experiments. The amount of acid which accumulatedin the initial period was increased by placing the leaves in5 per cent. CO₂ and also by decreasing the temperature from25 to 10°. In neither case were the nitrogen fractions affectedin a similar way to the acid levels. No consistent relationshipcould be found between the amount or change in amount of acidand the amounts of the nitrogen fractions. Over prolonged periodsthe drifts in the amounts of the nitrogen fractions were verysimilar to those known in non-succulent leaves. It is concludedthat, despite the large amounts of free acid and starch present,the nitrogen metabolism of detached Kalancho leaves in the darkis similar to that of non-succulent leaves. A possible explanationis suggested for the incorporation of ¹⁴C from ¹⁴CO₂ into nitrogenoussubstances in Kalancho leaves during dark acidification. Changesin the amounts of glutamine, which seemed to be related to oxygenuptake rather than to acid fluctuations, were measured in comparableleaf samples showing different rates of oxygen uptake. The rateof oxygen uptake of leaves and leaf disks in the dark was controlledby placing them in an atmosphere of nitrogen, or 5, 20, or 100per cent, oxygen, by the addition of 10^–3 M. cyanide,or by varying the temperature. At the end of a given periodthe amount of glutamine was always greater in the samples whichhad shown the higher rate of oxygen uptake during this perod.This correlation was found irrespective of whether the amountof glutamine had increased or decreased. With the assumptionsthat glutamine production and consumption were proceeding simultaneouslyand that the rate of consumption was unaffected by the rateof oxygen uptake, the experimental values are consistent withthe hypothesis that the rate of glutamine production and therate of oxygen uptake were directly related. The possible significanceof these findings is discussed.     

The Effect of Phytohormones on Chlorophyll(ide), Protochlorophyll(ide) and Carotenoid Formation in Greening Dark Grown Wheat Leaves

The influence of phytohormones on chlorophyll and carotenoid formation during the greening of irradiated dark grown wheat leaves (Triticum aestivum L. cv. Starke II Weibull) was studied. Leaves were floated on solutions of abscisic acid, gibberellic acid and kinetin for 24 h. The chlorophyll and carotenoid contents were determined during a subsequent period of 48 h of continuous irradiation. Leaves treated with abscisic acid showed a longer lag phase and a lower rate of accumulation of chlorophyll as compared to the control than did leaves treated with gibberellic acid and kinetin. The carotenoid content was low both in leaves treated with abscisic acid and in those treated with gibberellic acid. Treatment with abscisic acid lowered the protochlorophyllide regeneration after a saturating light flash while gibberellic acid as well as kinetin had no effect. The influence of ABA was partly dependent on an increase of the wounded part of the cut leaf segments. The accumulation of protochlorophyllide in leaves treated with δ-aminolevulinic acid was not affected by the different hormonal treatments. These results suggest that the main effect of abscisic acid is probably outside the chloroplast, i.e. on the formation or transport of δ-aminolevulinic acid.     

Sucrose-Induced Expression of Genes Coding for the Tuberous Root Storage Protein, Sporamin, of Sweet Potato in Leaves and Petioles

Sporamin, a major tuberous root protein of sweet potato, wasfound to accumulate in large quantities in excised leaves andpetioles when such explants were supplied with high concentrationsof sucrose. Although a small amount of sporamin could be detectedin leaves and petioles treated with 1% or lower concentrationsof sucrose, the maximum level of induction required sucroseat a concentration of 3% or higher. The appearance of sporaminpolypeptides in leaves and petioles treated with 3% sucrosefollowed a lag period of about one day, while a significantamount of sporamin mRNAs was already detectable in petiolesafter one day of treatment with sucrose. Addition of silvernitrate to the medium did not affect the accumulation of sporamin,suggesting that this induction is not due to the effect of ethyleneinduced by wounding of the tissue. The accumulation of sporamincould also be induced by glucose and by fructose, but not byman-nitol, suggesting that changes in carbohydrate and/or energymetabolism in the cell may be involved in the induction. Callustissues obtained by treatment of leaf segments with 1-naphthaleneaceticacid did not accumulate sporamin even though these cells werecultured on agar medium that contained 3% sucrose. However,when callus tissues were allowed to grow after transfer to amedium that contained 6-benzylaminopurine and sucrose, accumulationof large amounts of sporamin was induced. These results suggestthat, while expression of genes coding for sporamin can be inducedin organs other than the tuberous root by a process that doesnot accompany the differentiation of tissue, the induction ofexpression of sporamin genes by sucrose requires that cellsbe competent in some specific, but as yet unidentified, way. (Received August 27, 1990; Accepted November 5, 1990)     

Effects of Irradiance and Copper on the Activity of Ascorbate Oxidase in Detached Rice Leaves

The effects of copper on the activity of ascorbic acid oxidasc (AAO) in detached rice leaves under both light and dark conditions and in etiolated rice seedlings were investigated. CuSO₄ increased AAO activity in detached rice leaves in both light and darkness, however, the induction in darkness was higher than in the light. In the absence of CuSO₄, irradiance (40 μmol m^-2 s^-1) resulted in a higher activity of AAO in detached rice leaves than dark treatment. Both CuSO₄ and CuCl₂ increased AAO activity in detached rice leaves, indicating that AAO is activated by Cu. Sulfate salts of Mg, Mn, Zn and Fe were ineffective in activating AAO in detached leaves. CuSO₄ was also observed to increase AAO activity in the roots but not in shoots of etiolated rice seedlings. This revised version was published online in July 2006 with corrections to the Cover Date.     

BA、GA3和IAA对富士苹果果形形成的影响

以9年生富士苹果为材料,研究富士苹果形成过程中BA、GA,和IAA对果形、品质、内源激素含量的影响。结果表明：在花期喷GA,对富士苹果的坐果率影响效果最好,分别比清水对照和无处理对照提高49％和79．45％。BA100mg·L^-1GA3300mg·L^-1＋IAA20mg·L^-1对降低富士苹果偏斜率效果最好。在花期、花期＋幼果期和幼果期分别喷BA和在花期喷GA3可以提高果实中可溶性固形物的含量。花期喷IAA、BA、GA,和BA＋GA,＋IAA对内源激素IAA和GA3的含量均有促进作用,在整个生长季内不同处理下IAA、GA3含量均高于清水对照且差异明显;花期喷BA、GA3和BA＋GA3＋IAA对内源激素ZT含量有促进作用,尤其在果实幼果期和膨大期与清水对照相比效果明显;花期喷GA3和BA＋GA3＋IAA与清水对照相比内源激素ABA含量有明显降低,其中幼果期变化显著。     

Effect of Polyamines on Chlorophyll and Protein Contents, Photochemical Activity, and Energy Transfer in Detached Wheat Leaves during Dark Incubation

Spermine as compared to putrescine or spermidine retarded the loss of chlorophyll and protein contents to a greater extent in wheat primary leaves during dark incubation. Activities of whole chain electron transport, photosystem (PS) 1 and PS2, and absorbed excitation energy distribution in favour of PS 1 were protected by these amines in valency dependent manner during 72-h dark incubation.     

Stability of Milk Gangliosides and Formation of GD3 Lactone under Natural Acidic Conditions

To clarify the stability of milk gangliosides under natural acidic conditions in the stomach, the resistance of monosialoganglioside 3 (G_M3) and disialoganglioside 3 (G_D3) to gastric juice and acid solutions was investigated. The data presented here suggest that G_M3 and G_D3 in milk are likely to reach the intestinal tract because over 80% of the sialic acid in their structure remained intact under the same acidic conditions found in an infan?s stomach.     

Effects of O(2) Tension and Temperature during Light Uptake of CO(2) on the Dark Release of CO(2) by Excised C(3) and C(4) Leaves

A study was conducted on a C₄ (Panicum maximum) and a C₃ (Panicum bisulcatum) species to determine the nature of the dark release of ¹⁴CO₂ with respect to its responses to changes in temperature and O₂ tension during light CO₂ uptake of ¹⁴CO₂.