The developmental types of secretory cavities in Citrus remain unclear and whether or not programmed cell death is involved in the developmental process of secretory cavities remains an enigma. Regarding cavity formation in Citrus sinensis fruits, this work uncovered novel evidence to delineate secretory cavity formation in schizolysigeny, supporting the possibility of utilizing secretory cavities as a new cell biology model for investigating the molecular mechanism of plant programmed cell death.

Apoptosis. The role of the endonuclease

As the result of intensive research and breeding efforts over the last 20 years, the yield potential and yield quality of cereals have been greatly improved. Nowadays, yield safety has gained more importance because of the forecasted climatic changes. Drought and high temperature are especially considered as key stress factors with high potential impact on crop yield. Yield safety can only be improved if future breeding attempts will be based on the valuable new knowledge acquired on the processes determining plant development and its responses to stress. Plant stress responses are very complex. Interactions between plant structure, function and the environment need to be investigated at various phases of plant development at the organismal, cellular as well as molecular levels in order to obtain a full picture. The results achieved so far in this field indicate that various plant organs, in a definite hierarchy and in interaction with each other, are involved in determining crop yield under stress. Here we attempt to summarize the currently available information on cereal reproduction under drought and heat stress and to give an outlook towards potential strategies to improve yield safety in cereals.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2007.01727.x

The effect of drought and heat stress on reproductive processes in cereals.

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

The yield and quality of food crops is central to the well being of humans and is directly affected by climate and weather. Initial studies of climate change on crops focussed on effects of increased carbon dioxide (CO2) level and/or global mean temperature and/or rainfall and nutrition on crop production. However, crops can respond nonlinearly to changes in their growing conditions, exhibit threshold responses and are subject to combinations of stress factors that affect their growth, development and yield. Thus, climate variability and changes in the frequency of extreme events are important for yield, its stability and quality. In this context, threshold temperatures for crop processes are found not to differ greatly for different crops and are important to define for the major food crops, to assist climate modellers predict the occurrence of crop critical temperatures and their temporal resolution.

This paper demonstrates the impacts of climate variability for crop production in a number of crops. Increasing temperature and precipitation variability increases the risks to yield, as shown via computer simulation and experimental studies. The issue of food quality has not been given sufficient importance when assessing the impact of climate change for food and this is addressed. Using simulation models of wheat, the concentration of grain protein is shown to respond to changes in the mean and variability of temperature and precipitation events. The paper concludes with discussion of adaptation possibilities for crops in response to drought and argues that characters that enable better exploration of the soil and slower leaf canopy expansion could lead to crop higher transpiration efficiency.

/pdf/crop-responses-to-climatic-variation-weqbsghcx3.pdf

Crop responses to climatic variation

A compilation of studies using RAPD markers for evaluating population differentiation resulted in 78 estimates of AMOVA-derived Φ ST and 31 estimates of Nei's G ST , as well as in 41 estimates of Nei's within-population diversity. In outcrossing taxa, estimates of between-population diversity were closely correlated with maximum geographic distance between sampled populations. A corresponding association was not found in selfing taxa. These results suggest that RAPD can be a sensitive method for detection of genetic structuring according to the isolation-by-distance model. However, it also means that sampling strategies, as applied in individual studies, can seriously influence the resulting estimates of between-population diversity. Other sampling strategies, like number of plants per population and number of scored polymorphic markers, do not seem to impart any serious artefacts. As previously verified with allozyme data, RAPD markers showed that long-lived, outcrossing, late successional taxa retain most of their genetic variability within populations. By contrast, annual, selfing and/or early successional taxa allocate most of the genetic variability among populations. Estimates for between- and within-population diversity, respectively, proved to be negatively correlated, as previously reported for allozyme data. The only major discrepancy between allozymes and RAPD markers concerns geographic range; within-population diversity was strongly affected by distributional range of the investigated species in the allozyme data but not in the RAPD data. Moreover, RAPD-based values for between-population diversity increased with increasing distributional range whereas the opposite has been reported in a large allozyme data compilation. Contrary to allozymes, RAPD marker-derived within-population diversity is probably therefore not a very good predictor of total species genetic diversity.

Effects of life history traits and sampling strategies on genetic diversity estimates obtained with RAPD markers in plants

This study investigated whether pollen competition favours cross- over self-pollination in Eucalyptus globulus Labill. ssp. globulus. Controlled pollinations with self-pollen, cross-pollen and a mixture of self- and cross-pollen were conducted on three partially self-incompatible trees. The paternity of individual seeds resulting from mixed pollination was determined by isozyme analysis. No evidence for pollen competition was found. Instead, seed paternity reflected the level of self-incompatibility of each tree as determined by separate self- and cross-pollinations. Furthermore, the number of seeds set per capsule following mixed pollination was significantly less than that following cross-pollination in the two least self-compatible trees. These results suggest that both self- and cross-pollen tubes reach ovules following mixed pollination and that a late-acting self-incompatibility mechanism operates to abort a certain proportion of self-penetrated ovules.

Pollen competition does not affect the success of self-pollination in Eucalyptus globulus (Myrtaceae)

To examine the effect of early-climacteric (postripening) 1 -methylcyclopropene (1-MCP) exposure on the shelf-life and quality of green Cavendish bananas (Musa acuminata cv. Williams) from the middle section of the bunch, bananas were harvested bimonthly and treated with 100 μL L -1 ethylene for 2 consecutive days prior to exposure to 0, 100, 300, 1000, 3000 or 10 000 nL L -1 1-MCP for 24 h prior to storage at 22°C. 1-MCP treatment at a concentration of 300 nLL -1 or above increased banana shelf-life significantly compared with the control, regardless of the month in which fruit were harvested except March where a higher concentration was needed (3000 nL L -1 ). Fruit harvested in May were the most responsive with a greater than twofold increase in shelf-life. To examine the effect of fruit position in the bunch on 1-MCP efficacy, green fruit from the top or bottom of bunches were treated with 100 μL L -1 ethylene for 2 consecutive days prior to early-climacteric 1-MCP (300 nL L -1 ) exposure for 24 h at 22°C. In spring and autumn but not in summer, application of 1-MCP to early-climacteric fruit was more effective in fruit from the top than in those treated from the bottom of the bunch, increasing shelf-life. Firmness of 1-MCP-treated fruit was up to 19% greater than that of the control across the year, except in fruit from the bottom of the bunch. Given that 1-MCP is less effective in extending the shelf-life of summer-harvested fruit (particularly those from the bottom of the bunch), we conclude that preharvest conditions and fruit position in the bunch affect their responsiveness to ethylene and their behaviour during the ripening process.

Margaret Sedgley

Papers

Pollen competition does not affect the success of self-pollination in Eucalyptus globulus (Myrtaceae)

Variability of responses to 1‐methylcyclopropene by banana: influence of time of year at harvest and fruit position in the bunch

6-Benzylamino purine stimulates in vitro shoot organogenesis in Eucalyptus erythronema, E. stricklandii and their interspecific hybrids

Identification and investigation of relationships of mandarin types using isozyme analysis

Pollen Tube Pathway and Stimulation of Embryo Sac Development inPistacia vera(Anacardiaceae)