Analysis of developmental preformation in the alpine herb Caltha leptosepala (Ranunculaceae)

Developmental preformation is ubiquitous among alpine and arctic tundra plant species and may cause a delay in plant morphological responses to environmental variation. The duration of preformation and seasonal pattern of development were examined in Caltha leptosepala to identify characteristics of architecture and development that may influence the timing of plant responses to environmental cues, both within a single growing season and between years. All structures in C. leptosepala are preformed: leaves are initiated one or two growing seasons before they mature and flowers are initiated one growing season before maturation. Features of development and architecture in C. leptosepala, however, appear to differ from the determinate growth patterns of other exclusively preforming species, and may allow within-season variability in the seasonal development and maturation of structures. Cohorts of leaves initiated are asynchronous with maturation cohorts, and each year the number of leaf primordia per plant at snowmelt exceeds the number to mature aboveground. Therefore, some flexibility in whether leaves complete a 2-yr or 3-yr developmental trajectory might occur. Plasticity in reproductive phenotype might also occur via the process of floral abortion. Despite developmental characteristics that might facilitate the expression of phenotypic plasticity, only slight variability was observed in the duration of preformation or in the seasonal pattern of initiation and emergence of structures. Growth patterns of C. leptosepala thus appear to be fundamentally constrained, and limitations to annual growth may assure that sufficient preformed primordia remain belowground at the end of each growing season for maturation of a full cohort during the subsequent season.     

Extreme preformation in alpine Polygonum viviparum: an architectural and developmental analysis

Preformation, the initiation of organs one or more years prior to maturation and function, is reported to be common and crucial for plant survival in arctic and alpine environments, yet the phenomenon is remarkably little studied. In order to understand the role of preformation in the ecology and evolution of tundra species, this investigation takes a developmental and architectural approach to the analysis of plant growth and reproduction in the alpine perennial Polygonum viviparam L. Analyses show that the extent and duration of preformation in P. viviparam are extraordinary. Four years are required for each leaf and inflorescence to progress from initiation to functional and structural maturity. This single salient feature of development has profound consequences for basic architecture, dynamics of resource allocation, and the timing of plant responses to environmental variation. As a consequence of the protracted duration of leaf and inflorescence development, five cohorts of primordia, initiated in successive years, are borne simultaneously by an individual plant. In the year prior to maturation leaves reach 30% of their maximum size, and the maximum potential reproductive output of each inflorescence is determined. Thus, developmental processes that affect final morphology and resource allocation occur at least 1 yr before functional maturity. From the developmental and architectural models constructed for P. viviparum, a 1-yr delay in measurable plant responses to environmental variation is predicted. The models also apply generally to arctic and alpine species and provide a mechanistic explanation for observed patterns of productivity at the community and ecosystem scale.     

Sugars and flowering in the grapevine (Vitis vinifera L.)

Sugars play an important role in grapevine flowering. This complex process from inflorescence initiation to fruit maturity takes two growing seasons. Currently, most of the available data concern the involvement of sugars as energy sources during the formation of reproductive structures from initiation of inflorescences during the summer of the first year, until flower opening during the following spring. Sugars devoted to the development of reproductive structures are supplied either by wood reserves or by photosynthesis in leaves or inflorescences, depending on the stage of development. Female meiosis appears to be a key point in the success of flower formation because (i) flowers are vulnerable at this stage and (ii) it corresponds in the whole plant to the transition between reserve mobilization from perennial organs (roots, trunk, and canes) towards efficient leaf photosynthesis. The perturbation of reserve replenishment during the previous year provokes perturbation in the development of inflorescences, whereas altering the photosynthetic sources affects the formation of flowers during the same year. In particular, a lack of sugar availability in flowers at female meiosis caused by various environmental or physiological fluctuations may lead to drastic flower abortion. Apart from energy, sugars also play roles as regulators of gene expression and as signal molecules that may be involved in stress responses. In the future, these two topics should be further investigated in the grapevine considering the sensitivity of flowers to environmental stresses at meiosis.     

Some observations of phenology and ecophysiology ofDaphne kamtschatica Maxim.var.jezoensis (Maxim.) Ohwi, a shade deciduous shrub, in the forest of northern Japan

The phenology and leaf traits ofDaphne kamtschatica Maxim. var.jezoensis (Maxim.) Ohwi, the only summer deciduous shrub (20–40 cm) in the temperate forest of northern Japan, are examined. This plant carries through the winter mature leaves and well formed flower buds. It flowers in early spring during snowmelt and begins photosynthesis under relatively high irradiance under an open forest canopy. Our results show that there is significant carbon gain during the period when new leaves and fruit maturation also take place. Beginning in June, as the forest canopy closes, leaves onDaphne shoots senesce acropetally and the plants become completely bare in mid-July. After a period of 20-day dormancy, the shoots begin to resprout. Leaves become mature in early October and remain on the stem over winter. Leaf traits and photosynthesis measurements suggest as follows. 1) By becoming summer deciduous,D. kamtschatica avoids the cost of maintaining leaves inefficient under deep shade. 2) The onset and breaking of the summer dormancy is triggered by photoperiod since plants at the forest edge also become dormant even when light remained relatively high. However, the decreased duration of dormancy with higher light levels suggests that there is a tendency towards shorter dormancy where summer shade is absent and this could eventually lead to an evergreen habit such as that found in the alpine speciesDaphne miyabeana.     

Flowering dynamics of Orchis morio L. and Herminium monorchis (L.) R.Br, at two sites in eastern England

Information taken from two long-term demographic studies on Orchis morio L. and Herminium monorchis (L.) R.Br, is used to explore some of the factors which influence flowering. The proportion of plants which flowered each year varied considerably between species, flowering in O. morio exceeding 40% in all years except one over an 18 year period; over a 30 year period (1966–95), the number of plants of Herminium in flower never exceeded 36% of the population and no inflorescences were produced in 1977 and 1991. The relationship between flowering in Herminium in a given year and the monthly rainfall and temperature for the current and 3 previous years was analysed using logistic regression. Best fits were obtained using data for the summer months in the previous year, with an increasing flowering rate with rainfall and a decline with temperature. It is hypothesized that drought and high temperatures in the summer reduce leaf area and cause premature senescence and the death of leaves, with the result that not enough carbohydrates are stored to enable plants to support or initiate inflorescences the following year. For species such as Orchis morio which produce leaves in the autumn and remain green, summer drought causes no problems as they have no above ground organs. Factors which influence flowering in this species are as yet unknown.     

Seasonal aspects of the biology and diet of nearshore nototheniid fish at Potter Cove,South Shetland Islands,Antarctica

Summary Approximately 1000 specimens belonging to eight fish species were collected at Potter Cove, King George Island, South Shetland Islands, from August 1985 to May 1986. This study deals with the dominant species Notothenia neglecta, Notothenia gibberifrons, Trematomus newnesi and Notothenia rossii marmorata. Age and size structure of the fish were analyzed using scale and otolith readings. Notothenia neglecta was the most abundant species. It spawns in the austral autumn. Juvenile N. rossii marmorata migrate offshore when sexually mature. Over eight hundred stomach contents were analyzed. The four species studied were generally benthophagous. However, in summer T. newnesi and N. rossii marmorata, carried out vertical migrations, feeding on pelagic organisms. Gammarid amphipods constituted the main food in all four species. Algae were consumed regularly throughout the year and we suggest that they are intentially eaten by the fish, rather than by accident. Two 48 hour sampling periods, carried out in summer of 1987, showed that N. neglecta was more active during the day.     

Termination of nutrient import and development of vein loading capacity in albino tobacco leaves

The sink-source conversion in developing leaves of tobacco (Nicotiana tabacum L.) was studied to determine whether import termination is caused by the onset of export or is related to achievement of positive carbon balance. Albino shoots were grown in vitro and grafted to detopped stems of green tobacco plants. Termination of import was studied by providing mature leaves of the stock plant with ¹⁴CO₂ and detecting the presence of labeled nutrient in developing albino leaves by whole-leaf autoradiography. In albino leaves, import terminated progressively in the basipetal direction at the same stage of development as in leaves of green shoots. Starch was not present in the plastids of mesophyll cells of mature albino leaves but starch was synthesized when discs were cut from these leaves and incubated on 3 millimolar sucrose. Import ceased progressively in developing green leaves even when photosynthesis was prevented by darkening. It was concluded that cessation of import does not require achievement of positive carbon balance and is not the direct result of export initiation.

To determine whether vein loading capacity develops in albino leaves, discs were cut from mature leaves and floated on [¹⁴C]sucrose solution. Uptake of label into the veins was detected by autoradiography and this uptake was sensitive to the phloem loading inhibitor p-chloromercuribenzenesulfonic acid. However, the amount of label taken up by veins in albino leaves was less than that taken up by veins of mature green leaves.

     

Inflorescences vs leaves: a distinct modulation of carbon metabolism process during Botrytis infection

Plant growth and survival depends critically on photo assimilates. Pathogen infection leads to changes in carbohydrate metabolism of plants. In this study, we monitored changes in the carbohydrate metabolism in the grapevine inflorescence and leaves using Botrytis cinerea and Botrytis pseudo cinerea. Fluctuations in gas exchange were correlated with variations in chlorophyll a fluorescence. During infection, the inflorescences showed an increase in net photosynthesis (Pn) with a stomatal limitation. In leaves, photosynthesis decreased, with a non‐stomatal limitation. A decrease in the effective photosystem II (PSII) quantum yield (ΦPSII) was accompanied by an increase in photochemical quenching (qP) and non‐photochemical quenching (qN). The enhancement of qP and ΦPSII could explain the observed increase in Pn. In leaves, the significant decline in ΦPSII and qP, and increase in qN suggest that energy was mostly oriented toward heat dissipation instead of CO₂ fixation. The accumulation of glucose and sucrose in inflorescences and glucose and fructose in the leaves during infection indicate that the plant's carbon metabolism is differently regulated in these two organs. While a strong accumulation of starch was observed at 24 and 48 hours post‐inoculation (hpi) with both species of Botrytis in the inflorescences, a significant decrease with B. cinerea at 24 hpi and a significant increase with B. pseudo cinerea at 48 hpi were observed in the leaves. On the basis of these results, it can be said that during pathogen attack, the metabolism of grapevine inflorescence and leaf is modified suggesting distinct mechanisms modifying gas exchange, PSII activity and sugar contents in these two organs.     

Inflorescence of grapevine (Vitis vinifera L.): a high ability to distribute its own assimilates

The distribution of carbon (C) into whole grapevine fruiting cuttings was investigated during flower development to determine the relative contribution of inflorescence and leaf photoassimilates in the total C balance and to investigate their partitioning towards other plant organs. A (13)C labelling procedure was used to label C photoassimilates by leaves and inflorescences in grapevine. Investigations were carried out at various stages of flower/berry development, from separated cluster to fruit set, using grapevine fruiting cuttings with four leaves (Vitis vinifera L. cv. Chardonnay). This is the first study reporting that, during its development, (i) the carbon needs of the inflorescence were met by both leaf and inflorescence photosynthesis, and (ii) the inflorescence amazingly participated significantly to the total C balance of grapevine cuttings by redistributing an important part of its own assimilates to other plant organs. With regard to flowering, 29% of C assimilated by the inflorescence remained in the inflorescence, while partitioning towards the stem reached 42% and, as a lower proportion, 15% in leaves, and 14% in roots.     

Development of biochemical specialization and organelle partitioning in the single-cell C4 system in leaves of Borszczowia aralocaspica (Chenopodiaceae)

The terrestrial plant Borszczowia aralocaspica (Chenopodiaceae) has recently been shown to contain the entire C(4) photosynthesis mechanism within individual, structurally and biochemically polarized chlorenchyma cells rather than in a dual cell system, as has been the paradigm for this type of carbon fixation (Nature 414: 543-546, 2001). Analysis of carbon isotope composition and (14)CO(2) fixation shows that photosynthesis and growth of B. aralocaspica occurs through carbon acquired by C(4) photosynthesis. The development of this unique single-cell C(4) system in chlorenchyma cells was studied by analysis of young (0.2-0.3 cm length), intermediate (ca. 0.5-0.6 cm length), and mature leaves (ca. 3 cm length). The length of chlorenchyma cells approximately doubles from young to intermediate and again from intermediate to the mature leaf stage. In young chlorenchyma cells, there is a single type of chloroplast; the chloroplasts are evenly distributed throughout the cytosol, and all contain starch and rubisco. During leaf development, the activities of phosphoenolpyruvate carboxylase (PEPC; which is cytosolic), rubisco, and pyruvate,Pi dikinase (PPDK) increase on a chlorophyll basis. As leaves mature, chloroplasts differentiate into two distinct structural and biochemical types that are spatially separated into the proximal and distal parts of the cell (the proximal end being closest to the center of the leaf). The early stages of this polarization are observed in intermediate leaves, and the polarization is fully developed in mature leaves. The chloroplasts in the distal ends of the cell have reduced grana and little starch, while those at the proximal ends have well-developed grana and abundant starch. In mature leaves, PPDK is expressed in chloroplasts at the distal end of the cells, while rubisco and adenosine diphosphate glucose (ADPG) pyrophosphorylase are selectively expressed in chloroplasts at the proximal end of the cell. Mitochondrial polarization also occurs during development as nicotinamide-adenine dinucleotide phosphate-malic enzyme (NAD-ME) and the photorespiratory enzyme glycine decarboxylase are expressed in mature but not young leaves and are localized in mitochondria at the proximal end of the cells. The data show that single-cell C(4) develops from a single pool of identical organelles that develop differential biochemical functions and spatial partitioning in the cell during maturation.     

Why does Viola hondoensis (Violaceae) shed its winter leaves in spring?

? Premise of the study: Viola hondoensis is a perennial herb that inhabits the understory of temperate, deciduous forests. It is an evergreen plant with a leaf life span that is shorter than a year. Its summer leaves are produced in spring and shed in autumn; winter leaves are produced in autumn and shed in spring. Here we asked why the plant sheds its winter leaves in spring, though climate conditions improve from spring to summer. We proposed four hypotheses for the cause of shedding: (1) changes in seasonal environment such as day length or air temperature, (2) shading by canopy deciduous trees, (3) self-shading by taller summer leaves, and (4) competition for nutrients between summer and winter leaves. ? Methods: To test these hypotheses, we manipulated the environment of winter leaves: (1) plants were transplanted to the open site where there was no shading by canopy trees. (2) Petioles of summer leaves were anchored to the soil surface to avoid shading of winter leaves. (3) Sink organs were removed to eliminate nutrient competition. ? Key results: Longevity of winter leaves was extended when shading by summer leaves was eliminated and when sink organs were removed, but not when plants were transplanted to the open site. ? Conclusion: We conclude that the relative difference in light availability between summer and winter leaves is a critical factor for regulation of leaf shedding, consistent with the theory of maximization of the whole-plant photosynthesis.     

INFLORESCENCE TYPES AND FRUITING PATTERNS IN HAMLIN AND VALENCIA ORANGES AND MARSH GRAPEFRUIT

The structural, flowering, and fruit-setting patterns of inflorescences of mature Hamlin and Valencia orange and Marsh grapefruit trees were studied for three years. Several development patterns were found, some of which were relatively consistent for the different varieties or years of study. The sequence of anthesis on an inflorescence was: apical flower first, then basal flower, then the subapical flower. Terminals on which the earlier flowers appeared tended to have more inflorescences than those on which flowers appeared later. Inflorescences on which earlier flowers appeared also produced more flowers than those which began flowering later. Inflorescences that began flowering later were more likely to have leaves or have a greater number of leaves than earlier inflorescences. More than half of the inflorescences carried no leaves, and most of these had one flower. No evidence of a relationship between number of flowers and length of the inflorescence was found. Fruit set occurred primarily during the latter part of the flowering period. Many fruit were set on inflorescences without leaves, but on the basis of percent of flowers setting fruit, inflorescences with leaves were more productive. The greatest fruit set occurred in the subapical position on the inflorescence. With growth changes these fruit often appeared to be developing in the apical position. These patterns generally differed little from year to year. Variations may have been due to the differences in the number of flowers produced by the trees. Results were also similar between Hamlin and Valencia oranges. Patterns on Marsh grapefruit resembled those for the oranges but were frequently less consistent.     

Effect of light interception by non-photosynthetic organs on canopy photosynthetic production

A canopy photosynthesis model was derived on the assumption that the light diminution within a canopy is caused by both leaves and non-photosynthetic organs. The light diminution by leaves and that by non-photosynthetic organs were taken into account separately in the Lambert-Beer equation of light extinction. The light flux density on the leaf surface at each depth was evaluated from the leaf's share of light. The light flux density on the leaf surface thus obtained was incorporated into the Monsi-Saeki model of canopy photosynthesis. The proposed model was applied for estimating gross canopy photosynthesis in a 19-year-oldLarix leptolepis plantation where 38% of the light diminution was due to non-photosynthetic organs. The daily canopy photosynthesis on one summer day calculated using the present model was about 22% less than that calculated by the conventional Monsi-Saeki model, in which light interception by non-photosynthetic organs is neglected. The degree of such reduction in canopy photosynthesis through shading by non-photosynthetic organs was assessed in relation to parameters affecting light extinction, leaf photosynthetic characteristics, and light regime above the canopy.     

Midday depression of photosynthesis and effects of mist spray in citrus

Diurnal variations of gas exchange, chlorophyll a fluorescence and some related biochemical characteristics in sun-acclimated mature citrus leaves of mist-sprayed (treatment) and unsprayed (control) trees were compared on sunny days during summer to identify the environmental and physiological factors limiting carbon gain in citrus tree canopies. At midday, net photosynthesis and maximal photochemical efficiency of photosystem II ( F _v/ F _m) in citrus leaves decreased significantly under control conditions, but the decrease was mitigated by mist spraying. Although the content of malondialdehyde, hydrogen peroxide and activities of antioxidant enzymes increased at midday in both mist-sprayed and control leaves, they were much higher in control leaves than in mist-sprayed leaves. The level of D1 protein decreased significantly in control leaves at midday and then was partly recovered later, while that in treated leaves changed to a much lesser extent because of alleviation of photoinhibition by mist spraying. Both the fast and the slow phases of millisecond-delayed light emissions in treated citrus leaves were higher than those in control leaves, indicating that mist spraying protects the normal operation of the photosynthetic apparatus in leaves. Mist spraying also reduced leaf temperatures and the ratio of air to leaf vapour pressure deficit (ALVPD), leading to increases in stomatal conductance ( g _s) and alleviation of photoinhibition at midday. It is concluded that the decline of leaf g _s under high-ALVPD conditions in summer is an important factor contributing to midday depression of photosynthesis in citrus, and mist spraying is effective in alleviating midday depression of photosynthesis in citrus leaves.     

Does elevated atmospheric [CO2] alter diurnal C uptake and the balance of C and N metabolites in growing and fully expanded soybean leaves?

Increases in growth at elevated [CO2] may be constrained by a plant's ability to assimilate the nutrients needed for new tissue in sufficient quantity to match the increase in carbon fixation and/or the ability to transport those nutrients and carbon in sufficient quantity to growing organs and tissues. Analysis of metabolites provides an indication of shifts in carbon and nitrogen partitioning due to rising atmospheric [CO2] and can help identify where bottlenecks in carbon utilization occur. In this study, the carbon and nitrogen balance was investigated in growing and fully expanded soybean leaves exposed to elevated [CO2] in a free air CO2 enrichment experiment. Diurnal photosynthesis and diurnal profiles of carbon and nitrogen metabolites were measured during two different crop growth stages. Diurnal carbon gain was increased by c. 20% in elevated [CO2] in fully expanded leaves, which led to significant increases in leaf hexose, sucrose, and starch contents. However, there was no detectable difference in nitrogen-rich amino acids and ureides in mature leaves. By contrast to mature leaves, developing leaves had high concentrations of ureides and amino acids relative to low concentrations of carbohydrates. Developing leaves at elevated [CO2] had smaller pools of ureides compared with developing leaves at ambient [CO2], which suggests N assimilation in young leaves was improved by elevated [CO2]. This work shows that elevated [CO2] alters the balance of carbon and nitrogen pools in both mature and growing soybean leaves, which could have down-stream impacts on growth and productivity.     

N uptake and distribution in crops: an agronomical and ecophysiological perspective

The rate of N uptake of crops is highly variable during crop development and between years and sites. However, under ample soil N availability, crop N accumulation is highly related to crop growth rate and to biomass accumulation. Critical N concentration has been defined as the minimum N concentration which allows maximum growth rate. Critical N concentration declines during crop growth. The relationship between critical N concentration and biomass accumulation over the growth period of a crop is broadly similar within major C(3) and C(4) cultivated species. Therefore, the critical N concentration concept is widely used in agronomy as the basis of the diagnosis of crop N status, and allows discrimination between situations of sub-optimal and supra-optimal N supply. The relationship between N and biomass accumulation in crops, relies on the interregulation of multiple crop physiological processes. Among these processes, N uptake, crop C assimilation and thus growth rate, and C and N allocation between organs and between plants, play a particular role. Under sub-optimal N supply, N uptake of the crop depends on soil mineral N availability and distribution, and on root distribution. Under ample N supply, N uptake largely depends on growth rate via internal plant regulation. Carbon assimilation of the crop is related to crop N through the distribution of N between mature leaves with consequences for leaf and canopy photosynthesis. However, although less commonly emphasized, carbon assimilation of the crop also depends on crop N through leaf area development. Therefore, crop growth rate fundamentally relies on the balance of N allocation between growing and mature leaves. Nitrogen uptake and distribution also depends on C allocation between organs and N composition of these organs. Within shoots, allocation of C to stems generally increases in relation to C allocation to the leaves over the crop growth period. Allocation of C and N between shoots and roots also changes to a large extent in relation to soil N and/or crop N. These alterations in C and N allocation between plant organs have implications, together with soil availability and carbon assimilation, on N uptake and distribution in crops. Therefore, N uptake and distribution in plants and crops involves many aspects of growth and development. Regulation of nitrogen assimilation needs to be considered in the context of these interregulatory processes.     

Enhanced photosynthesis and flower production in a sagebrush morphotype associated with animal burrows

Two morphotypes of the evergreen shrub Artemisia tridentata Nutt. ssp. wyomingensis occur in the Shirley Basin of central Wyoming (USA), one of which was associated exclusively with Mima-like mounds generated by animal burrowing activity. Measured on a particularly dry year according to a 34-year precipitation record, plants growing on mounds (M) versus inter-mound locations (IM)were taller with greater leaf biomass and leaf area per unit ground area, and had over 90% of all inflorescences. As a result, the landscape consists of a patchy distribution of reproductive islands (~ 20-40 m^-2 in size) separated by a mean distance of ~ 30 m. In addition, greater photosynthesis per unit leaf area occurred for M plants when ephemeral leaves dominated total leaf area in spring and early summer, as well as during short time periods (< 3 days) following sporadic rainfall events in summer when only perennial leaves were present. As a result, estimated total annual carbon gain was 41% greater for M plants from May to mid-June, but was not significantly different from IM plants for the remainder of the season, resulting in a total summer carbon gain that was 14% greater in M plants. Stomatal and nonstomatal conductances to CO2 uptake were also greater for the ephemeral leaves of M plants, along with lower internal CO2 concentrations (193 ± 4 μl l^-1 vs. 209 ± 8 μl^-1, respectively). M plants also maintained higher xylem water potentials throughout most of the growth season (−1.1 ± 0.1 SD MPa in May, declining to −4.4 ± 0.3 SD MPa in August), along with higher water use efficiencies (photosynthesis/transpiration). M and IM soils did not differ significantly in total organic or nitrate contents, although leaf nitrogen content was higher in M plants when photosynthesis was also greater. Photosynthesis in M plants also responded more positively to afternoon showers greater than about 7 mm compared to IM plants. Thus, improved water and nutrient relations was associated with enhanced photosynthetic carbon gain in M plants, enabling greater flower production. Moreover, morphotypic plasticity coupled with the effects of animal burrows may have substantially increased sexual reproductive success in A. t. wyomingensis.     

Natural 13C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern

Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis‐based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C‐sinks have not been fully characterized yet. Here, we carried out extensive measurement of natural ¹³C‐abundance (δ¹³C) in oil palm tissues, including fruits at different maturation stages. We find a ¹³C‐enrichment in heterotrophic organs compared to mature leaves, with roots being the most ¹³C‐enriched. The δ¹³C in fruits decreased during maturation, reflecting the accumulation in ¹³C‐depleted lipids. We further used observed δ¹³C values to compute plausible carbon fluxes using a steady‐state model of ¹³C‐distribution including metabolic isotope effects (¹²v/¹³v). The results suggest that fruits represent a major respiratory loss (≈39% of total tree respiration) and that sink organs such as fruits are fed by sucrose from leaves. That is, glucose appears to be a quantitatively important compound in palm tissues, but computations indicate that it is involved in dynamic starch metabolism rather that C‐exchange between organs.     

Ethylene evolution from various developing organs of olive (Olea europaea) after excision

Ethylene evolution from leaves, stems, inflorescences and fruits of the olive plant ( Olea europaea L.) cv. Manzanillo was studied at various stages of their development. Mature non-growing organs, particularly leaves, have a constant, low, and uniform rate of ethylene evolution. Ethylene evolution from detached mature olive leaves was constant during the first 12 h after excision. Leaves on shoots maintained in vitro kept a constant rate of ethylene evolution for at least the first 5–6 days. Leaf injury significantly increased ethylene evolution. Ethylene evolution from injured and non-injured control leaves could be markedly inhibited aminoethoxyvinylglycine (AVG) applied to the leaves or fed to the shoot. The use of excised olive shoots and leaves as an in vitro model system for studies of induced metabolic processes such as abscission and developing water stress was suggested.