Effects of Prohexadione Calcium on growth and gibberellins contents of Chrysanthemum morifolium R. cv Monalisa White

The effect of Prohexadione Calcium (Pro-Ca) and daminozide was observed on the growth characteristics and endogenous gibberellin contents of Chrysanthemum morifolium R. cv Monalisa White. Three concentrations viz. 100, 200 and 400 ppm of Pro-Ca and a single concentration of daminozide (800 ppm) were applied three times with 7 days interval on three weeks old plant under greenhouse condition. Pro-Ca suppressed the plant length up to 30.7% while daminozide inhibited up to 27.12% at optimum concentration. The chlorophyll contents and stem diameter were higher than control, while the fresh weight and flower number insignificantly reduced with such treatments. Gibberellin (GA) analysis showed that Pro-Ca and daminozide application significantly lowered bioactive GA₁ content, although the amount of its immediate precursor GA₂₀ was fractionally higher. Bioactive GA₄ content was slightly higher than the control while significant difference in GA₉ was found between the plants treated with Pro-Ca and daminozide. Current study showed that both early C13 hydroxylation and non-C13 hydroxylation pathways of GA biosynthesis are operational in C. morifolium.     

Modeling plant morphology and development of petunia in response to temperature and photosynthetic daily light integral

The effects of mean daily temperature (MDT) and mean photosynthetic daily light integral (MDLI) on flowering during the finish stage of two petunia (Petunia × hybrida) cultivars were quantified. Petunia ‘Easy Wave Coral Reef’ and ‘Wave Purple’ were grown in glass-glazed greenhouses at 14–23 °C or 14–26 °C and under 4–19 mol m⁻² d⁻¹ with a 16-h photoperiod. The flower developmental rate was predicted using a model that included a linear MDT function with a base temperature multiplied by an exponential MDLI saturation function. The flower developmental rate increased and time to flower decreased as MDT increased within the temperature range studied. For example, under a MDLI of 12 mol m⁻² d⁻¹, as MDT increased from 14 to 23 °C, time to flower of ‘Easy Wave Coral Reef’ and ‘Wave Purple’ decreased from 51 to 22 d and 62 to 30 d, respectively. Flower developmental rate increased as MDLI increased until saturation at 14.1–14.4 mol m⁻² d⁻¹. Nonlinear models were generated for effects of MDT and MDLI on flower bud number and plant height at flowering. The number of flower buds at flowering increased as MDT decreased and MDLI increased. For example, at an MDT of 14 °C with 18 mol m⁻² d⁻¹, plants had 2.5–2.9 times more flower buds than those grown at 23 °C and 4 mol m⁻² d⁻¹. Models were validated with an independent data set, and the predicted time to flower, flower bud number, and plant height were within ±7 d, ±20 flowers, and ±4 cm, respectively, for 96–100%, 62–87%, and 93–100% of the observations, respectively. The models could be used during greenhouse crop production to improve scheduling and predict plant quality of these petunia cultivars.     

Calcium increases sodium exclusion in olive plants

‘Picual’ olive cuttings were grown in a greenhouse under saline conditions in 2 L plastic pots containing perlite. Plants were irrigated with a nutrient solution plus 75 mM NaCl and 0, 2.5, 10 or 40 mM CaCl₂. Vegetative growth, leaf and root Na⁺ and Ca²⁺ concentrations were measured. Na⁺ toxicity symptoms were observed in plants non-treated with Ca²⁺. Shoot length was higher in Ca²⁺ treated plants, although shoot growth was reduced at 40 mM CaCl₂, probably due to the high total ion concentration reached in the external solution. Ca²⁺ supply linearly increased leaf and root Ca²⁺ concentration and decreased leaf Na⁺ concentration. However, there were no differences in root Na⁺ concentration. Results indicate Ca²⁺ may take part in the Na⁺ exclusion mechanism, mainly preventing Na⁺ transport to the shoot, that may be an important ability for survival under saline conditions.     

Aneuploid strawberry (2n = 8x + 2 = 58) was developed from homozygous unreduced gamete (8x) produced by second division restitution in pollen

Unreduced gamete formation is significant in the evolutionary development of complex polyploidy series found in wild strawberry, genus Fragaria (Rosaceae). Also, it is important for genetics and breeding in strawberry plants to elucidate the mechanism of unreduced gamete formation. The objective of this study was to search for ploidy anomalies resulting from artificial diploid × octoploid crosses, and examine the mechanism through which these unreduced gametes were produced. Five everbearing cultivars of Fragaria vesca L. diploid (2n = 2x = 14) were crossed with pollen from six June-bearing cultivars of Fragaria × ananassa Duch., octoploid (2n = 8x = 56). A total of 3000 mature seeds, 100 from each of the 30 parental combinations were sown at 23 °C/20 °C (day/night) under artificial lighting with a 16 h day. The seedlings were transplanted to pots and grown in a greenhouse. Reproductive and morphological observations, flow cytometry analyses, chromosome counts and DNA analyses using CAPS markers were performed to identify the genetic background of the offspring. Most of the seed (79%) did not germinate or died soon after germination. Of the seedlings produced, 7% seemed to be pure F. vesca based on morphological characteristics, flow cytometry analyses and chromosome counts; 14% were pentaploids (2n = 5x = 35), 0.1% were hexaploids (2n = 6x = 42), and 0.03% (one individual) was aneuploid (2n = 8x + 2 = 58). Electrophoresis banding patterns obtained by CAPS marker analysis were heterozygotic in the 8x pollen parent but homozygotic in the aneuploid progeny. Judging from the chromosome counts and the CAPS marker analysis, the aneuploid was the result of a homozygous unreduced pollen grain (8x) crossed with an incomplete chromosome compliment from the egg. Because of the homozygosity, the unreduced male gamete must have been derived from second division restitution (SDR) in the octoploid pollen parent.     

Factors affecting mango (Mangifera indica L.) protoplast isolation and culture

The major factors influencing protoplast isolation and culture of mango (Mangifera indica L.) cv. Kensington Pride were investigated. The resultant protocol was used to compare plating efficiency among 4 mango cultivars. Most responses differed between proembryonic masses (PEMs) and leaf sources. Protoplast yields of 15.22 × 10⁶ g⁻¹ from PEMs and 8.68 × 10⁶ g⁻¹ from greenhouse-derived leaves were obtained in a solution of 0.7 M mannitol CPW plus 1.5% cellulase, 1% hemicellulase and 0.75% macerozyme for PEMs or 0.5 M mannitol CPW plus 1.5% cellulose, 1% hemicellulase and 1.5% macerozyme for leaves. Culture in Ca-alginate beads with initial plating densities (IPD) of 2.5 × 10⁴ Pp mL⁻¹ for PEMs and 2.5 × 10⁵ for leaves gave the highest plating efficiencies (FPE). For PEMs 1 mg L⁻¹ 2,4-d and 3.5 mg L⁻¹ kinetin gave an FPE of 2.85% whereas lower kinetin (2 mg L⁻¹) plus 0.5 mg L⁻¹ 6-BAP was most effective for leaves (FPE of 2.12%). Most protoplast mortality occurred during the first week of culture and was more severe in liquid culture. In Ca-alginate beads, protoplast survival at 14 days was higher for PEMs (30%) than leaf (21%) as was the frequency of cell division (17.6% compared to 13.6%). PEMs protoplasts continued development through embryogenesis to in vitro plantlet regeneration whereas leaf protoplasts underwent cell division up to 40-cell colonies but failed to proceed further. For PEMs, polyembryonic cvs. Kensington Pride and Keow Savoey produced higher FPE (1.95%) than monoembryonic cvs. Tommy Atkins and Keitt (1.75%). There was no effect of cultivar for leaf protoplasts.     

Effect of genotype,explant size,position, and culture medium on shoot generation of Gerbera jamesonii by receptacle transverse thin cell layer culture

An unique procedure for the mass shoot propagation of Gerbera using receptacle transverse thin cell layer (tTCL) culture procedure was developed. Genotype, flower bud age, explant size, position of receptacle tTCLs and culture media were found to affect the success of culture. Ten interspecific crosses of Gerbera showed different shoot regeneration rates and callus induction via receptacle tTCL culture, all of which had shoot regeneration rates higher than 57%. Flower buds collected on the 10th day resulted in 91% shoot regeneration after 6 weeks of culture on basal MS medium [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassay with tobacco tissue cultures. Physiol. Plant. 15, 475–497] supplemented with 0.02 mg l⁻¹ thidiazuron (TDZ), 0.8 mg l⁻¹ adenine and 10% (v/v) coconut water (CW). This was significantly higher than those from flower buds on the 7th and 14th days (22% and 54%), respectively. Shoot regeneration rate was the highest (94–100%) in the middle layers of the receptacle. For mass shoot propagation, shoot clusters were subcultured on half-strength MS medium supplemented with 0.5 mg l⁻¹ indole-3-butyric acid (IBA), 0.5 mg l⁻¹ 6-benzyladenine (BA) and 2.0 mg l⁻¹ kinetin after every 4 weeks. Plantlets formed when single shoots were cultured on half-strength MS medium containing 1 mg l⁻¹ IBA. All plantlets acclimatized well in the greenhouse.     

Models for predicting the mass of apricot fruits by geometrical attributes (cv. Shams,Nakhjavan, and Jahangiri)

Fruits with the similar weight and uniform shape are in high demand in terms of marketing value. Therefore, an awareness of grading fruit based on weight is crucial. A part of this research was aimed to present some physical properties of three Iranian apricot cultivars (Shams, Nakhjavan, and Jahangiri). In addition, apricot mass was predicted by different physical characteristics with linear and nonlinear models as three different classifications: (1), single or multiple variable regressions of apricot dimensional characteristics. (2), single or multiple variable regressions of apricot projected areas and (3), estimating apricot mass based on its volume. All properties considered in the current study were found to be statistically significant at the 1% probability level. The highest and the lowest dimensional characteristics were found for Jahangiri and Nakhjavan cultivars, respectively. Sphericity values had significant difference among the tested cultivars. The latter property values were 0.971, 0.917, and 0.973 for Shams, Nakhjavan, and Jahangiri cultivars, respectively. Based on the results, the surface area of the Jahangiri cultivar was found to be 6458.35 mm², followed by the Shams and Nakhjavan cultivars, which had a mean of 6115.36, and 4395.25 mm², respectively. In this paper, the coefficients of static friction of the cultivars on three different surfaces are also reported. The results showed that mass modeling of apricot based on minor diameter and three projected areas are the most appropriate models in the first and the second classifications, respectively. In third classification, the best model was obtained on the basis of the actual volume as M = 0.997V_m + 0301, R² = 0.98, R.S.E. = 1.711 with R² = 0.98. It was concluded that the suitable grading system of apricot mass is based on minor diameter as nonlinear relation: M = 0.0019c^2.693, R² = 0.96, R.S.E. = 2.2.     

Paclitaxel-producing fungal endophyte stimulates the accumulation of taxoids in suspension cultures of Taxus cuspidate

Fusarium mairei, a paclitaxel-producing fungal endophyte, its effects on taxoid synthesis in Taxus cells were investigated via adding the fungal endophyte culture supernatants (FECS) to the suspension cultures of Taxus cuspidata. The concentration of FECS was determined on its total carbohydrate. When 100 mL of Taxus cell suspension cultures were treated with several dosages of FECS (4, 6 and 8 g) at day10, the cultures treated with 6 g FECS produced the highest yield of paclitaxel (5.84 mg L⁻¹), which was 1.8-fold the yield from controls (3.14 mg L⁻¹). The major elicitor element in FECS was an oligosaccharide of 2 kDa. In addition, the cultures treated with 6 g FECS resulted in 25.86 mg L⁻¹ of the precursor 10-deacetylbaccatin III (10-DAB) accumulation, which was 11 times that of control cultures (2.32 mg L⁻¹), and 4.7 times higher than that of cultures treated with 200 μM methyl jasmonate (MJ) (5.43 mg L⁻¹). These results indicate that FECS favors to stimulate 10-DAB accumulation more effectively than paclitaxel accumulation.     

Nitrate uptake kinetics of grapevine under root restriction

To examine the effect of root restriction on the nitrate uptake and the nitrate transport system activity, 2-year old “Fenghou” grapevines (Vitis Vinifera × V. Labrasca) were planted in pots with volume 2 L and 12 L served as root restriction and the control, respectively. The pots were filled with perlite and watered with rainwater and nutrient solution. Vine growth and kinetics of nitrate uptake in vine roots were evaluated. The results showed that root restriction significantly inhibited the shoots and roots growth, enhanced the nitrate uptake rate, decreased the kinetics parameter K_m value and increased V_max value, that is to say, root restriction depressed the affinity of nitrate high-affinity transport system (HATS) and improved the nitrate uptake rates of both high (HATS) and low-affinity transport system (LATS). However, root restriction significantly decreased the amount of net nitrate uptake, which led to the low nitrate concentration in leaves and roots.     

Earthworm casts as an alternate carrier material for biofertilizers: Assessment of endurance and viability of Azotobacter chroococcum, Bacillus megaterium and Rhizobium leguminosarum

Vermicast was used with lignite in different combinations (0:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1 and 1:0) as carrier substrate for biofertilizers (Azotobacter chroococcum, Bacillus megaterium and Rhizobium leguminosarum). The viability count of biofertilizer organisms in stored carrier material was individually carried out once in 15 days for a total period of ten months. More than 1 × 10⁷ g⁻¹ viable cells of A. chroococcum, B. megaterium and R. leguminosarum were observed in 4:1, 5:1, 6:1 and 1:0 combination of carrier materials (vermicast:lignite) at the end of 10th month. In case of lignite carrier material, no viable cells were observed in 10⁷ g⁻¹ at the end of 6th month for A. chroococcum and R. leguminosarum and 5th month for B. megaterium. The correlation of viable cells of the biofertilizers was negative with reference to incubation period. The increase of vermicast proportion in carrier materials showed increase in the survival rate. The results of the present study suggest that the vermicasts can be used as an alternate carrier material for A. chroococcum, B. megaterium and R. leguminosarum.     

Changes in morphological phenotypes and essential oil components in lavandin (Lavandula × intermedia Emeric ex Loisel.) transformed with wild-type strains of Agrobacterium rhizogenes

Hairy roots were induced from leaf-derived calli of lavandin (Lavandula × intermedia Emeric ex Loisel.) by infection with wild-type strains of Agrobacterium rhizogenes, A-5 (MAFF 02-10265) and A-13 (MAFF 02-10266). A-5-inoculated calli formed hairy roots more efficiently than A-13 ones. The transgenic shoots could be obtained from hairy root segments mediated by each Agrobacterium strain. However, different plant growth regulators were required for efficient adventitious shoot formation in each strain. In A-5, the most efficient adventitious shoot formation rate of 23.8% was observed in a medium with 4.4 × 10⁻⁶ M of 6-benzylaminopurine. On the other hand, a significantly higher rate of 13.2% was detected in a medium with 4.0 × 10⁻⁷ M of N-(2-chloro-4-pyridyl)-N′-phenylurea in A-13. Most of the regenerated plants showed dwarfism with closed internodes and extensive lateral branching, which were typical characteristics of ‘hairy root syndrome’. On the other hand, only nine of the 45 regenerated plants formed flower buds in early June, a delay of about one month compared with nontransgenic regenerated plants. The floral stalks and spikes of these plants were very short, resulting in a compacted form. Many regenerants showed a significantly lower productivity of essential oil than nontransgenic regenerants. Moreover, the relative percentage of the linalyl-cation-derived compounds, linalool and linalyl acetate, decreased in most of the regenerated plants. Compact plants with the ability of flower bud formation are assumed to be valuable not only for lavandin breeding, but also for clarifying the interaction between rol genes expression and essential oil production.     

Spatial and temporal oxygen distribution measured with oxygen microsensors in growing media with different levels of compaction

Oxygen microsensors were used to determine oxygen profiles in situ from the top to the bottom layer of the growing medium for potted plants of Rosa sp. ‘Dior’. The growing medium was peat- based and compacted uniformly to 3 different bulk densities of 0.14, 0.18 and 0.23 g cm⁻³ (0, 20 and 40% compacted, respectively). The water distribution in the pot was determined as water content (g cm⁻³) in the top, middle and bottom layers of the peat. Oxygen content was also determined after a standard subirrigation cycle and after excessive irrigation where the bottom of the pots were left waterlogged for 24 h. Measurements were carried out at 5.5 weeks during the production phase and at 12 weeks at the end of the production. The results showed that with increasing compaction and density, more water was transported to the upper layers of the pot. After a standard irrigation cycle there was no effect of the level of medium compaction on the oxygen distribution, whereas after excessive irrigation, the oxygen contents at the bottom of the pots were strongly reduced and the level of compaction significantly affected oxygen availability. The most compacted medium had the lowest oxygen content at 5.5 weeks, with anoxic conditions in the bottom 30 mm. Plant quality measured as fresh weight, dry weight, height and number of shoots with flowers and buds was not affected by the different levels of compaction. The use of oxygen microsensors provided a new insight into the spatial and temporal distribution of oxygen in growing media and how this was affected by the physical characteristics of the growing media.     

Auxin-dependent development and habituation of highbush blueberry (Vaccinium × covilleanum But. et Pl.) ‘Herbert’ in vitro shoot cultures

The influence of IAA (1.0 mg dm⁻³), and IBA (1.16 mg dm⁻³), on the development of highbush blueberry (Vaccinium × covilleanum But. et Pl.) ‘Herbert’ in vitro shoot cultures was examined. Depending on the kind of auxin and 2iP concentration in vitro cultures consisted of various number of axillary (AX) and adventitious (AD) shoots. Three different categories of AD shoots were found: leaf shoots (AD-L), node-adjoin shoots (AD-P), and base-adjoin shoots (AD-M, madshoots). The AX shoots were the least habituated (towards auxins, cytokinins and vitamins) whereas the AD-M shoots (madshoots) the most. In comparison to IAA, IBA caused dying or callusing higher number of initial explants. However, IBA generally suppressed development of AD shoots, especially madshoots whereas slightly weakened multiplication of AX shoots. IBA significantly enhanced elongation of AX shoots also. Axillary shoots obtained on IBA-media had relative long internodes and rigid, well-developed leaves. The adventitious shoots, especially base-adjoin (AD-M) ones, were easily distinguishable as were more thin and fragile, more or less vitrified, and had short internodes and smaller, sometimes unfolded leaves. Development of blueberry in vitro cultures on auxin-free and IAA-supplemented media was similar. AX shoots grown on such media resembled AD shoots. 2iP applied in higher doses along with IAA promoted much proliferation of AD than AX shoots. In contrast, 2iP applied in higher doses together with IBA stimulated significantly only growth of AX shoots whereas in general, development of adventitious shoots was not affected. Micropropagation carried out through routine method based on subculturing of shoot explants or shoot clumps on the medium supplemented with IAA (4 mg dm⁻³) and 2iP (10–15 mg dm⁻³) as well as stimulation of shoot elongation on the blank medium causes in fact the propagation of highbush blueberry through highly habituated adventitious madshoots. Replacement of IAA by IBA facilitates micropropagation of highbush blueberry cv. Herbert through axillary shoots.     

Production protocol development for greenhouse cut Linaria, Lupinus, and Papaver flowers

Linaria maroccana Hook. f. Ann., ‘Lace Violet’, Lupinus hartwegii ssp. cruikshankii Lindl. ‘Sunrise’ and Papaver nudicaule L. ‘Meadow Pastels’ seeds were directly sown into 105 cell plug trays and received either ambient light or supplemental high intensity discharge (HID) lighting. For each species, a 2 × 3 × 3 factorial was used with two light intensities during propagation, three transplant stages, and three night temperatures. Seedlings were transplanted at the appearance of 2–3, 5–6, or 8–9 true leaves. Transplanted Linaria and Papaver seedlings were placed at 5/11, 10/16, or 15/21 ± 1 °C night/day temperatures and Lupinus seedlings were placed at 15/24, 18/25, or 20/26 ± 2 °C night/day temperatures. For this study, the optimum production temperature for Linaria was 10/16 °C as the cut stems produced at 15/21 °C were unmarketable and production time was excessively long at 5/11 °C. At 10/16 °C, Linaria seedlings should be transplanted at the 2–3 leaf stage to maximize stem number, stem length and profitability. For Lupinus the optimum temperature was 15/24 °C due to long stems and high profitability per plant. Lupinus seedlings should be transplanted at the 2–3 leaf stage when grown at 15/24 °C to obtain the longest and thickest stems; however, $/m² week was higher for plants transplanted at the 8–9 leaf stage due to less time in finishing production space. For Papaver, the 15/21 °C temperature was optimal as that temperature produced the longest stems in the shortest duration, resulting in the highest $/m² week. At 15/21 °C Papaver plants should be transplanted at the 2–3 leaf stage. Supplemental HID lighting had no effect on any of the species.     

Factors affecting haploid induction through in vitro gynogenesis in summer squash (Cucurbita pepo L.)

Haploid production using in vitro ovule cultures has long been recognized as an important tool to produce haploid and homozygous double-haploid plants for genetic studies and plant breeding programs. In the present study, four experiments were carried out to study the influence of genotype, position of female flowers on plant stem, temperature and sucrose concentration on the in vitro gynogenesis induction of squash. (1) Ovules of 12 genotypes were excised from female flowers, 1 day before anthesis, and cultured onto MS medium containing 3% sucrose and 1 mg l⁻¹ from each of kinetin and 2,4-D (2,4- dichlorophenoxy acetic acid). Differences in response among genotypes were demonstrated. Raad F₁ showed the highest percentage of responding ovules and number of plantlets per dish with 48.8% and 15 plants, respectively. The results revealed that genotype is a key factor influencing the in vitro gynogenesis in squash. (2) Ovules were excised from first, second and third female flower of two hybrids (Giad and Raad) and cultured onto the mentioned above medium. The highest percentage of responding ovules and number of plantlets per dish were obtained from ovules excised from the second female flower on the plant stem. (3) Effect of temperature (4 and 32 °C) for 0, 4, 7 and 12 days on the ovule culture of Queen F₁ was studied. Ovules incubated at 4 or 32 °C for 4 days produced a better embryogenic response. (4) Three sucrose concentrations (30, 60 and 90 g l⁻¹) were tested with the ovule cultures of the local cultivar (Eskandrani). Differences among sucrose concentrations were statistically significant and ovules cultured on the MS medium containing 30 g l⁻¹ produced the best result. MS medium containing 90 g l⁻¹ did not produce gynogenic ovules.     

Fruit growth,cuticle deposition,water uptake,and fruit cracking in jostaberry,gooseberry, and black currant

Fruit cracking after rain limits the production of a number of crops, including some Ribes species. To gain a better understanding of the factors involved in cracking, fruit growth, deposition of the cuticular membrane (CM), water uptake and fruit cracking were studied in black currant (Ribes nigrum L. cv. Zema), gooseberry (Ribes uva-crispa L. cv. Rote Triumph), and jostaberry (Ribes nidigrolaria B. cv. Jostine). Fruit surface area and fresh mass increased continuously throughout development, whereas deposition of the CM was biphasic. CM mass per fruit increased rapidly up to 42, 41, and 49 days after full bloom (DAFB) in black currant, gooseberry, and jostaberry, respectively. Thereafter, CM mass per fruit remained constant in gooseberry and jostaberry or increased at a lower rate in black currant. The cessation of or reduced rate of CM deposition resulted in a decrease in CM mass per unit area in all berries. Elastic strain of the CM at maturity averaged 23.8% and 19.5% in gooseberry and jostaberry, respectively, and only 8.2% in black currant. Microcracks in the CM were observed first in gooseberry and jostaberry 64 DAFB, whereas there were no microcracks in black currant. Water uptake into mature detached berries was linear over 2 h of incubation. Rates of uptake were highest in gooseberry followed by black currant and jostaberry. Relative uptake was similar via the cut end of the pedicel (32.1%), the apex of the fruit (34.7%) and the fruit surface (33.2%). Rates of water uptake through the fruit surface were positively related to surface area. Average fruit water potential for black currant, gooseberry, and jostaberry was −2.14 ± 0.17, −1.24 ± 0.03, and −1.89 ± 0.20 MPa, while the permeability for osmotic water uptake was 7.7 ± 0.4 × 10⁻⁸, 5.2 ± 0.1 × 10⁻⁸, and 3.3 ± 0.3 × 10⁻⁸ m s⁻¹. Incubating whole fruit in deionized water for 72 h resulted in more cracked jostaberries (94%) than black currants (74%) or gooseberries (50%). A comparison of our findings in Ribes berries with published data for the sweet cherry drupe revealed that the berries fitted the relationships established in sweet cherry among fruit growth, cuticle deposition, strain of the cuticle, microcracking, permeability for osmotic water uptake, frequency of stomata and cracking. The Ribes berries were less susceptible to cracking than sweet cherry.     

The influence of desiccation and rehydration on the survival of polyembryonic seed of Citrus suhuiensis cv. limau madu

A study was carried out to investigate the influence of desiccation and freezing followed by various presowing rehydration procedures on the desiccation sensitivity of the seed of Citrus suhuiensis cv. limau madu. The freshly harvested seeds of limau madu were desiccated under a broad range of relative humidity (RH) to various equilibrium water contents (g H₂O g⁻¹ dw). The desiccated and desiccated–frozen seeds were either directly sown under germination conditions or subjected to presowing rehydration procedures: seed preheating, prehumidification and osmoconditioning. The hydrated and desiccated seeds were sown in controlled germination conditions and the survival was evaluated 4–6 weeks after sowing. The results showed that desiccation progressively reduced the percentage of normal seedling of the seeds of limau madu and the viability is almost lost at water contents below 0.08 g H₂O g⁻¹ dw. The estimated desiccation sensitivity was substantially high (WC₅₀ = 0.143 g H₂O g⁻¹ dw) when the desiccated seeds were rapidly rehydrated (uncontrolled rehydration). In contrast, seed prehumidification, preheating and osmoconditioning (controlled rehydration procedures) markedly enhanced normal seedling percentages decreasing the estimated values of WC₅₀ (between 0.08 and 0.127 g H₂O g⁻¹ dw). While the rapidly rehydrated desiccated–frozen seeds were almost killed at water content of 0.15 g H₂O g⁻¹ dw, prehumidification and preheating have noticeably increased percentage of frozen seeds survival at the same water content. However, at water content of 0.21 g H₂O g⁻¹ dw preheating significantly (P < 0.05) increased percentage of normal seedling of the frozen seeds. Seed desiccation markedly reduced the percentages of germinated seeds with multiple seedlings. Seed controlled rehydration remarkably increased the survival of polyembryos. The beneficial effect of seed controlled rehydration on the survival of the desiccated seeds was pronounced at medium water contents (0.08–0.25 g H₂O g⁻¹ dw).     

Development of a plant regeneration system from seed-derived calluses of centipedegrass [Eremochloa ophiuroides (Munro.) Hack]

The objective of this study is to establish plant regeneration system with the seed of the new Chinese selection “E-126”of centipedegrass [Eremochloa ophiuroides (Munro.) Hack] as explant. In present study, the following results were obtained: (1) The medium formulation most suitable for calluses induction was identified to be MS with 1.0 mg l⁻¹ 2,4-D + 30 g l⁻¹ mannitol + 50 ml l⁻¹ coconut milk and the ratio of calluses induction was 96.0%, including 5.2% of yellow granule calluses induction. The above medium formulation was adopted for subculture. (2) The rate of shoot regeneration from yellow granular calluses was 98.0% by MS optimum medium formulation with 2.0 mg l⁻¹ KT + 50 ml l⁻¹ coconut milk. The differentiated rate retained as high as 88.0% even after 5 times of subculture and 18.6% after 15 times of subculture. The optimum medium formulation for shoot growth was identified to be MS medium plus 2.0 mg l⁻¹ BAP, 0.8 mg l⁻¹ NAA and 50 ml l⁻¹ coconut milk. (3) The optimum medium for shoot rooting was identified to be MS medium with 0.6 mg l⁻¹ NAA + 50 ml l⁻¹ coconut milk, and the rooting rate to be 98.0%. The survival rate of transplanted plantlets from tubes to basin with soil was 92.0%. In conclusion, the plant regeneration system was successfully developed in this study, which may provide basic reference for screening of somaclonal variants and genetic transformation of centipedegrass.     

Evaluation of the effectiveness of soil-applied plant derivatives of Meliaceae species on nitrogen availability to peach trees

We assessed the effect of soil-applied derivatives of melia (Melia azedarach L.) and neem (Azadirachta indica A. Juss) on nitrogen (N) soil availability, root uptake and peach (Prunus persica L.) growth. First we evaluated the effectiveness of experimentally prepared amendments made with fresh ground melia leaves or commercial neem cake incorporated into the soil as nitrification inhibitors, then we evaluated the effect of fresh ground melia fruits and neem cake on growth and N root uptake of potted peach trees, and on soil microbial respiration. Soil-applied fresh ground melia leaves at 10 and 20 g kg⁻¹ of soil as well as commercial neem cake (10 g kg⁻¹) were ineffective in decreasing the level of mineral N after soil application of urea-N as a source of mineral N, rather they increased soil concentration of nitric N and ammonium N. The incorporation into the soil of fresh ground melia fruits (at 20 and 40 g kg⁻¹) and neem cake (at 10 and 20 g kg⁻¹) increased N concentration in leaves of GF677 peach × almond (Prunus amygdalus) hybrid rootstock alone or grafted with one-year-old variety Rome Star peach trees. An increase in microbial respiration, leaf green color and plant biomass compared to the control trees were also observed. The Meliaceae derivatives did not affect, in the short term (7 days), N root uptake efficiency, as demonstrated by the use of stable isotope ¹⁵N, rather they promoted in the long term an increase of soil N availability, N leaf concentration and plant growth.     

Responses of eight chile peppers to saline water irrigation

Salt tolerance of five cultivars of Capsicum annuum L. Early Jalapeno, Golden Treasure, NuMex Sweet, NuMex Joe E. Parker, and Santa Fe Grande, two cultivars of C. chinense Jacq. Habanero and Pimienta De Chiera, and one accession of C. annuum, NMCA 10652, were evaluated in a field study. Seedlings were transplanted in late May to field raised beds containing loamy sand soils in a semi-arid environment. Plants were well irrigated throughout the experiment. Three saline solution treatments, prepared by adding NaCl, MgSO₄, and CaCl₂ to tap water at different amounts to create three salinity levels of 0.82 dS m⁻¹ (control, tap water), 2.5 dS m⁻¹, and 4.1 dS m⁻¹ electrical conductivity (EC), were initiated on 15th June and ended in late August. Among the eight varieties, NMCA 10652 had the highest survival percentage at 100% in the 4.1 dS m⁻¹ treatment, followed by ‘Early Jalapeno’, ‘NuMex Sweet’, ‘Pimienta De Chiera’, ‘Santa Fe Grande’, ‘Golden Treasure’, and ‘NuMex Joe E. Parker’. ‘Habanero’ had the lowest survival at 28%. Compared to control, final shoot dry weight of the plants irrigated with saline solution at 4.1 dS m⁻¹ was reduced by 92% in ‘Habanero’, followed by ‘Golden Treasure’ at 80%. For fruit fresh weight in 4.1 dS m⁻¹ vs. control, ‘Habanero’ had the highest reduction at 86%, followed by ‘Golden Treasure’ at 74%, while NMCA 10652 and ‘Santa Fe Grande’ had the least at 26% and 19%, respectively. NMCA 10652, the most tolerant to salinity, had the lowest leaf Na⁺ accumulation, while ‘Habanero’, the most sensitive to salinity, had the highest Na⁺ in the leaves. For leaf Cl⁻, ‘Early Jalapeno’ had the highest, while ‘Habanero’ had the lowest Cl⁻ accumulation in the leaves. Generally, sensitive varieties accumulated more Na⁺ and/or Cl⁻ in leaves, except for ‘Early Jalapeno’, which was relatively tolerant to salinity but had high Na⁺ and Cl⁻ accumulation in leaves.