A rapid field method for measuring net assimilation rate-stomatal conductance relationship: a feasibility test using grapevine leaves

Based on the assumption that the response time of the photosynthetic apparatus to changes in light intensity is faster than the response time of stomata, a rapid field method for measuring the assimilation rate (A) stomatal conductance (g_s) relationship in wine-grapes is proposed. Leaves from the outer canopy of Vitis vinifera L. cultivar ‘Cabernet sauvignon’ were placed between two pieces of foam for 90 min to reduce light intensity and induce stomatal closure, while allowing water vapor diffusion to occur. Heat load was reduced by shading the foam with a piece of light colored, heavy paper attached to the foam with a 10 mm air space between them. When the cover was removed, A and g_s were measured several times until no significant changes in g_s were observed. The A/g_s relationships of the leaves were similar in spite of differences in the response time between leaves. Very few exceptions to the A/g_s curves existed, and these leaves were easily identified. This procedure permits an analysis of the A/g_s relationship without the complications of different plant water potentials that are normally used to achieve different levels of g_s.     

Floral induction in longan (Dimocarpus longan, Lour.) trees: IV. The essentiality of mature leaves for potassium chlorate induced floral induction and associated hormonal changes

This study was conducted to elucidate the function of leaves and their role in the alteration of plant hormone homeostasis during potassium chlorate (KClO₃) induced “off season” floral induction (FI) of longan. KClO₃ application had almost no effect on the concentration of gibberellins in receptive apical and lateral shoot meristems, whereas the auxin IAA initially decreased, but later remarkably increased. The most significant changes caused by KClO₃ treatments was an increase in zeatin/zeatin-riboside (Z/ZR) type cytokinins (CKs) 8 days after treatment in the shoot apical and close by lateral buds as well as in the tissue beneath these buds. The 6–7-fold increase in CK concentrations were greatly reduced in the absence of leaves (leaves removed between the apical bud and a girdle). A significant exception was a strong accumulation of isopentenyl adenine/isopentenyl adenosine (iP/iPA) type CKs in wood and bark beneath the bud of defoliated shoots that were isolated against the rest of functional leaves of the tree by a girdle. This accumulation of iP/iPA, the immediate precursors of Z/ZR, together with the strong increase of Z/ZR in the shoot apical bud (SAB) after KClO₃ application indicate that leaves may be involved in the biosynthesis of CKs. Overall, the results suggest that cytokinins play a significant role in KClO₃ induced “off season” floral induction in longan. This role may not be restricted to the biosynthesis of these hormones but also to their mobilization and accumulation in the SAB of newly flushing shoots.     

A novel in vitro hydroponic culture system for potato (Solanum tuberosum L.) microtuber production

An innovative in vitro hydroponic culture system used in potato (Solanum tuberosum L.) microtuber production is described in this paper. In vitro potato plantlets, 6–8 cm in height, derived from meristems of potato tubers cultured on 1/2 Murashige and Skoog (MS) nutrient medium after 30 days culture were cut into 1.5 cm stem node segments and used as explants. These stem nodes were cultured in a novel system called in vitro hydroponic culture system containing 1/2 MS medium supplemented with 0.5 μM naphthaleneacetic acid (NAA), 0.3 μM gibberellic acid (GA₃), 3.7 μM adenine sulfate, 10% coconut water, 0.5 g/l activated charcoal, 80 g/l sucrose with or without 8 g l⁻¹ agar. Liquid medium was distributed to the carrier substrates in each storey of the system with the aid of capillary robes. In the present paper, the effects of porous material used as substrate carrier and the number of storeys involved in the culture system on microtuber formation and their morphological characteristics are reported. Cotton layer substrate is more stable for organogenesis of potato microtubers. Microtubers, 3.19 mm in diameter and 49.82 mg in weight, could be harvested from a one-storey in vitro hydroponic culture system containing filter paper as substrate. However, microtubers cropped from three-storey in vitro hydroponic culture system with cotton layer were bigger and weightier than those from three-storey system containing filter paper. The above results of the in vitro hydroponic system examined in this study might open up a new approach in producing potato and other hygrophilous microtuber.     

Induction and scale-up of Billbergia zebrina nodule cluster cultures: Implications for mass propagation,improvement and conservation

The Tropical Atlantic Rain Forest is a biome of high diversity and endemism of plant genetic resources. High diversity of bromeliad species occurs in this biome, but part of them is now endangered. Tissue culture based techniques comprise valuable tools for the mass propagation and conservation of endangered bromeliads. In the present work the in vitro regenerative system based on the induction and development of NC from nodal segments of Billbergia zebrina showed different morphogenetic features from those observed in organogenesis and somatic embryogenesis. Different levels of TDZ, NAA, and 2i-P promoted the induction of NC with different morphologies and regenerative potential. NC induced in response to 0.01 μM of TDZ and subcultured on BM free of PGR resulted in high regenerative frequency. NC originated from BM supplemented with TDZ (0.1 μM) when subcultured on BM with NAA (2 μM) and 2-iP (4 μM) resulted in higher mean number of shoots. Elongated shoots were successfully acclimatized in ex vitro conditions and derived plantlets had normal phenotype. Histological analyses revealed the morphogenesis of the NC related to organization of the meristematic zone in the subepidermic region composed by organized layers with small and isodyametric cells followed by the induction of shoot buds. SEM analysis showed that the induction of NC occurred from the basal region of the explants.     

Adventitious shoot regeneration from hypocotyl slices of mature apricot (Prunus armeniaca L.) seeds: A feasible alternative for apricot genetic engineering

Adventitious shoot regeneration from hypocotyl slices of mature apricot seeds has been achieved with regeneration percentages of 31.7%, 44.4%, and 46.9% for the cultivars ‘Canino’, ‘Dorada’, and ‘Moniqui’, respectively. Regeneration was significantly affected by the parental origin of the explants (P < 0.05) but not by thidiazuron or 3-indolebutyric acid for any of the three cultivars, at the levels tested. None of the other factors studied (basal medium, 2,4 dichlorophenoxy-acetic acid pulses, dark incubation period, or addition of silver thiosulfate) affected significantly shoot regeneration percentage from ‘Canino’ hypocotyl sections. The effect of paromomycin on regeneration was genotype-dependent and different dose–response curves were obtained for each cultivar. While 40 μM paromomycin completely inhibited regeneration from ‘Canino’ sections, some buds were obtained from ‘Dorada’ and ‘Moniqui’ explants. The two aminoglycoside antibiotics tested, kanamycin and paromomycin, showed differing toxicity on ‘Canino’. A lower concentration of kanamycin (20 μM) than of paromomycin inhibited totally adventitious regeneration from ‘Canino’ explants. Agrobacterium-mediated transformation experiments, with the non-oncogenic strain AGL1 harboring the binary plasmid p35SGUSINT, were performed and GUS assays were carried out after four weeks to determinate stable transformation events. The utilization of paromomycin (10 μM) as the selective agent increased significantly both the number of explants that presented at least one transformation event (P < 0.05) and the number of large area or calli expressing the gus gene (P < 0.001), compared with the addition of kanamycin (10 μM). Moreover, when 10 μM paromomycin was added to the medium some massively transformed explants were observed and a chimerical bud was regenerated.     

Evaluation and correction of nutrient availability to Gerbera jamesonii H. Bolus in various compost-based growing media

Nutrient deficiencies usually constrain the use of some composted materials as peat-substitute growing media even if some fertilizer is applied to the media. In this work, we assessed the suitability of various composted materials as such or mixed with peat for potted plant production, with special emphasis on their effects on nutrient availability to plants. Further, we examined the effect of vivianite [Fe₃(PO₄)₂·8H₂O] as a fertilizer and its mixture with humic substances (HS) on these growing media (particularly their effectiveness in preventing Fe deficiency chlorosis in alkaline substrates). A completely randomized experiment design was developed involving the growth of gerber (Gerbera jamesonii H. Bolus) and two factors, namely (i) the growing medium, specifically composted cork residue (C), compost obtained from a mixture of olive husk and cotton gin trash mixed with rice hulls and peat in a 1:1:1 volume proportion (OH), composted grape marc (GM), Sphagnum peat mixed with spent mushroom compost (M), coconut fibre (CF), and Sphagnum peat; and (ii) the Fe source (control without Fe, Fe-EDDHA, vivianite and vivianite + HS in a weight ratio of 10:1).