Much has been written about theory and practice in the law, and the tension between practitioners and theorists. Judges do not cite theoretical articles often; they rarely "apply" theories to particular cases. These arguments are not revisited. Instead the Essay explores the working and interaction of theory and practice, practitioners and theorists. The Essay starts with a story about solving a legal issue using our intellectual tools - theory, practice, and their progenies: experience and "gut." Next the Essay elaborates on the nature of theory, practice, experience and "gut." The third part of the Essay discusses theories that are helpful to practitioners and those that are less helpful. The Essay concludes that practitioners theorize, and theorists practice. They use these intellectual tools differently because the goals and orientations of theorists and practitioners, and the constraints under which they act, differ. Theory, practice, experience and "gut" help us think, remember, decide and create. They complement each other like the two sides of the same coin: distinct but inseparable.

Of Theory and Practice

INTRODUCTION. Internal Organization of the Plant Body. Summary of Types of Cells and Tissues. General References. DEVELOPMENT OF THE SEED PLANT. The Embryo. From embryo to the Adult Plant. Apical Meristems and Their Derivatives. Differentiation, Specialization, and Morphogenesis. References. THE CELL. Cytoplasm. Nucleus. Plastids. Mitochondria. Microbodies. Vacuoles. Paramural Bodies. Ribosomes. Dictyosomes. Endoplasmic Reticulum. Lipid Globules. Microtubules. Ergastic Substances. References. CELL WALL. Macromolecular Components and Their Organization in the Wall. Cell Wall Layers. Intercellular Spaces. Pits, Primary Pit--Fields, and Plasmodesmata. Origin of Cell Wall During Cell Division. Growth of Cell Wall. References. PARENCHYMA AND COLLENCHYMA. Parenchyma. Collenchyma. References. SCLERENCHYMA. Sclereids. Fibers. Development of Sclereids and Fibers. References. EPIDERMIS. Composition. Developmental Aspects. Cell Wall. Stomata. Trichomes. References. XYLEM: GENERAL STRUCTURE AND CELL TYPES. Gross Structure of Secondary Xylem. Cell Types in the Secondary Xylem. Primary Xylem. Differentiation of Tracheary Elements. References. XYLEM: VARIATION IN WOOD STRUCTURE. Conifer Wood. Dicotyledon Wood. Some Factors in Development of Secondary Xylem. Identification of Wood. References. VASCULAR CAMBIUM. Organization of Cambium. Developmental Changes in the Initial Layer. Patterns and Causal Relations in Cambial Activity. References. PHLOEM. Cell Types. Primary Phloem. Secondary Phloem. References. PERIDERM. Structure of Periderm and Related Tissues. Development of Periderm. Outer Aspect of Bark in Relation to Structure. Lenticels. References. SECRETORY STRUCTURES. External Secretory Structures. Internal Secretory Structures. References. THE ROOT: PRIMARY STATE OF GROWTH. Types of Roots. Primary Structure. Development. References. THE ROOT: SECONDARY STATE OF GROWTH AND ADVENTITIOUS ROOTS. Common Types of Secondary Growth. Variations in Secondary Growths. Physiologic Aspects of Secondary Growth in Roots. Adventitious Roots. References. THE STEM: PRIMARY STATE OF GROWTH. External Morphology. Primary Structure. Development. References. THE STEM: SECONDARY GROWTH AND STRUCTURAL TYPES. Secondary Growth. Types of Stems. References. THE LEAF: BASIC STRUCTURE AND DEVELOPMENT. Morphology. Histology of Angiosperm Leaf. Development. Abscission. References. THE LEAF: VARIATIONS IN STRUCTURE. Leaf Structure and Environment. Dicotyledon Leaves. Monocotyledon Leaves. Gymnosperm Leaves. References. THE FLOWER: STRUCTURE AND DEVELOPMENT. Concept. Structure. Development. References. THE FLOWER: REPRODUCTIVE CYCLE. Microsporogenesis. Pollen. Male Gametophyte. Megasporogenesis. Female Gametophyte. Fertilization. References. THE FRUIT. Concept and Classification. The Fruit Wall. Fruit Types. Fruit Growths. Fruit Abscission. References. THE SEED. Concept and Morphology. Seed Development. Seed Coat. Nutrient Storage Tissues. References. EMBRYO AND SEEDLING. Mature Embryo. Development of Embryo. Classification of Embryos. Seedling. References. Glossary. Index.

Anatomy of Seed Plants

Phenology affects nearly all aspects of ecology and evolution. Virtually all biological phenomena—from individual physiology to interspecific relationships to global nutrient fluxes—have annual cycles and are influenced by the timing of abiotic events. Recent years have seen a surge of interest in this topic, as an increasing number of studies document phenological responses to climate change. Much recent research has addressed the genetic controls on phenology, modelling techniques and ecosystem-level and evolutionary consequences of phenological change. To date, however, these efforts have tended to proceed independently. Here, we bring together some of these disparate lines of inquiry to clarify vocabulary, facilitate comparisons among habitat types and promote the integration of ideas and methodologies across different disciplines and scales. We discuss the relationship between phenology and life history, the distinction between organismal- and population-level perspectives on phenology and the influence of phenology on evolutionary processes, communities and ecosystems. Future work should focus on linking ecological and physiological aspects of phenology, understanding the demographic effects of phenological change and explicitly accounting for seasonality and phenology in forecasts of ecological and evolutionary responses to climate change.

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Toward a synthetic understanding of the role of phenology in ecology and evolution

In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

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In Posidonia oceanica cadmium induces changes in DNA methylation and chromatin patterning

Gibberellins (GAs) function not only to promote the growth of plant organs, but also to induce phase transitions during development. Their involvement in flower initiation in long-day (LD) and biennial plants is well established and there is growing insight into the mechanisms by which floral induction is achieved. The extent to which GAs mediate the photoperiodic stimulus to flowering in LD plants is, with a few exceptions, less clear. Despite evidence for photoperiod-enhanced GA biosynthesis in leaves of many LD plants, through up-regulation of GA 20-oxidase gene expression, a function for GAs as transmitted signals from leaves to apices in response to LD has been demonstrated only in Lolium species. In Arabidopsis thaliana, as one of four quantitative floral pathways, GA signalling has a relatively minor influence on flowering time in LD, while in SD, in the absence of the photoperiod flowering pathway, the GA pathway assumes a major role and becomes obligatory. Gibberellins promote flowering in Arabidopsis through the activation of genes encoding the floral integrators SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), LEAFY (LFY), and FLOWERING LOCUS T (FT) in the inflorescence and floral meristems, and in leaves, respectively. Although GA signalling is not required for floral organ specification, it is essential for the normal growth and development of these organs. The sites of GA production and action within flowers, and the signalling pathways involved are beginning to be revealed.

Gibberellin as a factor in floral regulatory networks

The intention of this review is to discuss floral initiation of horticultural trees. Floral initiation is best understood for herbaceous species, especially at the molecular level, so a brief overview of the control of floral initiation of Arabidopsis (Arabidopsis thaliana (L.) Heynh.) precedes the discussion of trees. Four major pathways to flowering have been characterized in Arabidopsis, including environmental induction through photoperiod and temperature, autonomous floral initiation, and regulation by gibberellins. Tropical trees are generally induced to flower through environmental cues, whereas floral initiation of temperate deciduous trees is often autonomous. In the tropical evergreen tree mango, Mangifera indica L., cool temperature is the only factor known to induce flowering, but does not ensure floral initiation will occur because there are important interactions with vegetative growth. The temperate deciduous tree apple, Malus domestica Borkh., flowers autonomously, with floral initiation dependent on aspects of vegetative development in the growing season before anthesis, although with respect to the floral initiation of trees in general: the effect of the environment, interactions with vegetative growth, the roles of plant growth regulators and carbohydrates, and recent advances in molecular biology, are discussed.

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Regulation of floral initiation in horticultural trees

Post-pruning shoot growth increases fruit abscission and reduces stem carbohydrates and yield in macadamia

We investigated the effects of the timing of shoot elongation on the flowering of lychee (Litchi chinensis Sonn.) in eastern Australia. Trees of cv. Kwai May Pink growing in Alstonville (lat. 28.9° S) were pruned during spring and summer, and subsequent shoot elongation was measured until the following spring. New shoots grew by discrete flushes, with the trees initiating 3, 2, or 1 vegetative shoots prior to winter, according to the pruning sequence. Shoots were vegetative when the mean temperature during early flush development was above 17-19°C, and floral at lower temperatures. Trees with successive flushes commencing in February (late summer) and June (early winter) were more likely to flower than trees with flushes commencing in April and August, because the weather conditions in June were cooler than those in August and more likely to favour induction. The importance of cool weather conditions during early flush development for floral determination was not significantly affected by the number of vegetative flushes to develop between pruning and winter. Having shown that the phase of recurrent flushing affects flowering, we sought to model the process in order to recognise reproductive and non-reproductive cycles along Australia's north-eastern seaboard, and to develop a management strategy for the promotion of flowering. From the results of the Alstonville pruning trial, the interval between successive flushes was regressed against the mean product of daily irradiation and mean daily temperature (°C.MJ/[m2.day]) during the interval. The regression was used in conjunction with long-term weather records to estimate the flush commencement dates required for the completion of 1 or 2 vegetative flushes by the winter solstice at different latitudes. The earliest date for the completion of 1 flush ranged from 16 February in northern New South Wales (lat. 30° S) to 13 March in northern Queensland (lat. 17° S). To test the model, a pruning trial was conducted near Mareeba (lat. 17° S). Trees pruned on 10 February, estimated to produce ≈ 1.5 flushes prior to winter (i.e. flushes in late autumn and early spring, but not in winter), flowered poorly and had low yields. In contrast, trees pruned on 11 March, estimated to produce 1 vegetative flush by winter, had good flowering and yields. Thus, strategic pruning after harvest can be used to manipulate flushing times, so that new, potentially flowering shoots emerge in winter. Cool temperatures are still required for successful flowering, and we provide estimates of the likelihood of such weather in the major growing areas by calculating the annual number of days with a mean temperature <20°C. For Cairns (lat. 16.9° S) the number of such days varied from 0 to 39 from 1888 to 1993, which is consistent with the irregular flowering of lychee in coastal northern Queensland. Our work is the first demonstration for any species that the phase of recurrent flushing affects flowering, and emphasises the interplay between a plant's endogenous developmental cycle and seasonal variations in weather.

Flowering and shoot elongation of lychee in eastern Australia

Orchard trees of A4 macadamia (Macadamia integrifolia × tetraphylla) and Hass avocado (Persea americana) were thinned and tip-pruned at different times to generate a range of trees with different stages of leafy flush development. The stagger in the start of the first flush following pruning was repeated in the start of subsequent flushes, so pruning was an effective means of changing the phase of the cycle of flush development. The difference in phase affected flowering. In macadamia, over 80% of the variance in flowering was explained by regression against pruning time. Flowering ranged from 0 to 43% of tip-pruned branches, with the most profuse flowering on flushes appearing in July. In avocado, over 45% of the variance in flowering of the first flush following pruning, and over 35% of the second flush, was explained by regression against pruning time, with more flowering on those flushes starting nearer to the winter solstice. The control trees flowered better than the pruned trees but there was too little information to explain the difference. The macadamia control trees had less synchronised flushing than the pruned trees, and were not subject to internal thinning. The avocado control trees appeared to have a phase of flush development different from the pruned trees, with a summer flush commencing before the first pruning date and maturing before the maturation of the first post-pruning flushes. More research is needed for related canopy management guidelines.

The timing of flush development affects the flowering of avocado (Persea americana) and macadamia (Macadamia integrifolia × tetraphylla)

Macadamia (Macadamia integrifolia Maiden and Betche, M. tetraphylla Johnson and hybrids) orchards in Australia are typically hedged around anthesis (September). Such hedging reduces yields, largely through competition for carbohydrates between early fruit set and the post-pruning vegetative flush, but also through a reduction in photosynthetic capacity caused by the loss of canopy. We examined whether hedging at other times might mitigate yield losses. Hedging time was found to affect yields across four cultivars: ‘A4’, ‘A38’, ‘344’ and ‘816’. Yield losses were lower for trees hedged in November–December than for trees hedged in September. Yields for trees hedged in June were higher than for trees hedged in September in one experiment, but were similar in a second experiment. Yield losses for September and October hedging were similar. Hedging time changed the pattern of fluctuations in stem water-soluble carbohydrates (WSC). WSC declined shortly after hedging in September, October or November, and the declines preceded increases in fruit abscission relative to unpruned control trees. The increase in fruit abscission was less pronounced for the trees hedged in November, consistent with the idea that fruit become less sensitive to carbon limitation as they mature.

Trevor Olesen

Papers

Regulation of floral initiation in horticultural trees

Post-pruning shoot growth increases fruit abscission and reduces stem carbohydrates and yield in macadamia

Flowering and shoot elongation of lychee in eastern Australia

The timing of flush development affects the flowering of avocado (Persea americana) and macadamia (Macadamia integrifolia × tetraphylla)

Time of pruning affects fruit abscission, stem carbohydrates and yield of macadamia.