Morphological characterisation of the floral nectary in some apple-shaped and pear-shaped quince cultivars

The receptaculo-ovarial nectary of quince is located on the adaxial surface of the hypanthium. The glandular tissue is protruding out of the basal part of the receptacular tissue, but the apical part of the nectary is epimorphic. The glands can have various shapes if observed in the median longitudinal section of the flower and gland shapes are characteristic to the cultivars. The anisodiametrical cells of the nectarial epidermis are arranged in one or two rows. The surface of the nectary is covered by cuticle, the thickness of which depends on climatic conditions. Stomata of the nectary are mesoxeromorphic, the guard cells are sunken below the outer anticlinal wall of the epidermis cells. The investigated pear-shaped quince cultivars have more sunken stomata than the apple-shaped ones. Both the glandular tissue and the nectary parenchyma are the thickest on the basal part of the nectary, but taper on the apical part. The nectary parenchyma cells differ from the receptacular ones in shape and size. The phloem bundles, supplying the nectary, do not enter into direct contact with the secretory tissues.The morphological and histological differences that can be found between the nectary of cvs. ‘Konstantinápolyi’ and cvs. ‘Dunabogdányi’, as well as between the gland of the investigated apple-shaped cultivars and pear-shaped ones, can have taxonomic importance and could refer to the various degree of susceptibility of the cultivars to Erwinia amylovora

Floral biological investigations of apple cultivars in relation to fire blight

Floral activity was studied in two apple cultivars: an Erwinia-tolerant (Treedorn') and a sensitive one (`Sampion'). Since more types of protogyny occur in apples, the period of stigma activity is different. Papillae of the exposed stigma in flowers of 'Freedom' function longer (usually more than a week) than in the delayed homogamous `Sampion'. Despite of this, cv. 'Freedom' is tolerant to Erwinia amylovora (Burr.) Winslow et al., suggesting no relationship between the floral biological type (including the exposure and longevity of stigma) and the infection by E. amylovora. According to SEM micrographs, nectary stomata in `Freedom' are already open in the flower bud, where nectar secretion starts and continues until the senescence of the stigma. However, the long period of nectar secretion does not create optimal conditions for bacterial growth, since nectar production is scant in the flowers of 'Freedom'. The surface of the nectary, its nectar-retaining capacity, and the amount and concentration of nectar may influence the susceptibility of apple cultivars. It is manifested well by the smooth nectary surface with nectary stomata rising slightly above the epidermis in flowers of cv. 'Freedom', contrasting the wrinkled, striate nectary surface with slightly sunken stomata in the flowers of 'Sampion'

Histological study on the leaf rehydration of desiccation-tolerant plant Xerophyta scabrida

Water uptake and water use efficiency of poikilochlorophyllous resurrection plants considerably differ from other vascular plants due to their special ecological adaptation strategies. Histological traits of the living and dead leaves of desiccation-tolerant Xerophyta scabrida (Pax) Th., Dur. et Schinz. were investigated after safranin staining to examine the dynamics of rehydration and the process ofwater transport by safranin impregnation differences. Staining that appeared on the leaf's surface epidermal glands after 30 min of remoistening in living X. scabrida leaves suggested that glandular complexes could take part in the water uptake from the beginning of the rehydration process, when the xylemmight not have been filled up, yet. The leaves of living X. scabrida became fully impregnated faster than the dead leaves: Sclerenchyma staining started from the xylem while dead X. scabrida leaves were not able to rehydrate fully. The dynamics of rehydration by the orientation of immersing leaveswas also studied. Leaves immersed into the solution with their base downward became fully impregnated earlier than the leaves sank into the dye with their apex downward. Faster water supply in the former case might have been related to the earlier recovery of xylem integrity and the resultant spatially continuous water supply. The results indicate that the living leaves of desiccation-tolerant X. scabrida were able to uptake significantwater amount not only (and not primarily) through their vascular tissues but by external water conduction. Due to the specific binding of safranin to lignifying cell walls and its fast spread from the xylem to the sclerenchymatous bundle sheaths also confirm the potential role of sclerenchyma in the water movement of leaf tissues

Ecophysiological and Anatomical Mechanisms behind the Nurse Effect: Which Are More Important? A Multivariate Approach for Cactus Seedlings

BACKGROUND: Cacti establish mostly occurs under the canopy of nurse plants which provide a less stressful micro-environment, although mechanisms underlying this process are unknown. The impact of the combination of light and watering treatments on Opuntia streptacantha (Cactaceae) seedlings was examined. METHODS/PRINCIPAL FINDINGS: Ecophysiological [titratable acidity, osmotic potential (‘solute potential’, Ψ(s)), relative growth rate (RGR) and their components (NAR, SLA, and LWR)], anatomical (chloroplast density, chloroplast frequency, and cell area), and environmental [photosynthetic photon flux density (PPFD) and air temperature] sets of variables were analyzed, assessing relationships between them and measuring the intensity of the relationships. Three harvests were carried out at days 15, 30, and 45. Ψ(s) and acidity content were the most important responses for seedling establishment. The main anatomical and environmental variables were chloroplast density and water availability, respectively. Opuntia streptacantha seedlings establish better in the shade-watering treatment, due to higher Ψ(s) and acidity, unaffected chloroplasts, and lower PPFD. In addition, the chloroplasts of cells under high-light and non-watering treatment were clumped closer to the center of the cytosol than those under shade-drought, to avoid photoinhibition and/or to better distribute or utilize the penetrating light in the green plant tissue. CONCLUSIONS: Opuntia seedlings grow better under the shade, although they can tolerate drought in open spaces by increasing and moving chloroplasts and avoiding drastic decreases in their Ψ(s). This tolerance could have important implications for predicting the impact of climate change on natural desert regeneration, as well as for planning reforestation-afforestation practices, and rural land uses