Flowers underpin plant evolution, genetic legacy and global food supply. They are exposed to similar evaporative conditions as leaves, yet floral physiology is a product of different selective forces. We used Tanacetum cinerariifolium, a perennial daisy, to examine the response of flowers to whole-plant water stress, determining if flowers constitute a liability during drought, and how this species has adapted to minimize risk associated with reproduction.We determined the relative transpiration cost of flowers and leaves and confirmed that flowers in this species are xylem-hydrated. The relative water stress tolerance of leaves and flowers then was compared using xylem vulnerability measurements linked with observed tissue damage during an acute drought treatment.Flowers were a major source of water loss during drought but the xylem supplying them was much more vulnerable to cavitation than leaves. This xylem vulnerability segmentation was confirmed by observations that most flowers died whereas leaves were minimally affected during drought.Early cavitation and hydraulic isolation of flowers during drought benefits the plant by slowing the dehydration of perennial vegetative organs and delaying systemic xylem damage. Our results highlight the need to understand flower xylem vulnerability as a means of predicting plant reproductive failure under future drought.

Rain induced fruit cracking in sweet cherries takes 3 distinct forms: stem end cuticular fractures, calyx end cuticular fractures, and large cracks usually deep into the pulp on the cheek of the fruit. A 4-year study of sweet cherry varieties from a commercial orchard in Tasmania, Australia, was conducted to investigate the incidence of crack type and its relative likelihood, as influenced by both genotype and season. Although all 3 crack types developed in the 3-week period before commercial harvest, the extent of cracking was strongly controlled by season. While initial development of cracks coincided with rainfall, no relationship between amount of rain and incidence of cracking was found for crack type. A significant relationship was found between the tangential stress experienced by fruit skin from fruit at harvest maturity and the incidence of cracking recorded in the orchard. No other fruit property (pulp osmotic potential, fruit diameter, weight) explained the differences in incidence of cracking in the field between seasons or varieties. The results suggest that management of cracking needs to consider both varietal and seasonal factors. The development of turgor in maturing fruit also needs further investigation.

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& Context High temperature stress in nurseries germinating Eucalyptus globulus seed is an important problem affecting germination synchrony and rate. Where there is a risk of hightemperature stress, then the choice of female parent may be important. This issue is particularly relevant to the production of full-sib families from mass-supplementary pollination where there may be opportunities for seed producers to manipulate the directionality of the crossing done in seed orchards.& Aims This study aimed to quantify the maternal versus paternal influence of seed sensitivity to high temperature stress during germination. & Methods A diallel crossing scheme involving four genotypes was used to test the relative importance of male and female genetic influences on the germination and development of E. globulus seed and their response to high temperature stress. Seed was germinated at optimum (25°C) and supra-optimal (32°C and 37°C) temperatures, and six traits

Low capsule set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Trials were conducted in E. globulus seed orchards in Tasmania, Australia, to identify the timing of capsule development and abortion, as well as the influence of pollination type, the number of ovules fertilised and weather events on capsule set. Controlled pollination (CP), mass supplementary pollination (MSP), open pollination (OP) and isolated unpollinated control (UP) treatments were performed on 21 genotypes in an orchard in southern Tasmania in 2004–2005 and on six genotypes in a higher-altitude orchard in north-western Tasmania in 2005–2006. No capsules were set in the UP control treatment, and capsule set was significantly lower following CP than OP and MSP. The major period of capsule abortion occurred between 20 and 80 days after pollination for all pollination methods across both sites, coinciding with the period of capsule growth. A positive correlation between the number of fertilised ovules per aborted capsule and the length of time capsules were held on the tree was recorded. Given that capsule abortion occurred during a period of fruit growth and that capsules with the lowest number of fertilised ovules aborted first, it is argued that fertilisation level and the level of resource competition are major factors determining capsule abortion.