Growth,root morphology and boron uptake by citrus rootstock seedlings differing in boron-deficiency responses

Boron (B) is an essential microelement for higher plants and has important physiological functions in plant growth and development. Citrus plants are frequently exposed to B-deficiency, but knowledge regarding the effects of B-deficiency on rootstock growth, root morphology and genotypic variations in citrus is limited. To evaluate the variations in plant-growth parameters in response to B-deficiency, five citrus rootstocks seedlings that grown in modified 1/2-strength Hoagland's solution that contained 0.25 μM H₃BO₃ (moderate B-level, Control) or 0 μM H₃BO₃ (B-deficiency, −B) were investigated before and 90 days after treatment. There are significant genotypic variations in plant-growth parameters (dry mass, leaf area and seedling height), root-morphological traits and B-concentrations. B-deficiency inhibited plant dry mass and leaf area expansion of Fragrant citrus, Sour orange and Trifoliate orange seedlings significantly (P < 0.05), whereas no effect was found on the total dry mass of Carrizo citrange and Red tangerine seedlings. Further, B-deficiency reduced the root number, root length and root surface area in Fragrant citrus and Trifoliate orange significantly (P < 0.05); however, no significant effect was detected on these root morphological traits of Carrizo citrange and Red tangerine (P > 0.05). In addition, B-deficiency reduced the B-concentration in the leaves of all the five genotypes and the B-concentration in the roots of Fragrant citrus and Sour orange, none effect was observed on the B-concentration in stems of all studied genotypes and roots. However, there were significant relationships between the root-morphological traits and B-uptake efficiency. These results showed that Carrizo citrange and Red tangerine are B-efficient, Trifoliate orange is the moderate B-efficient genotypic rootstocks, whereas Fragrant citrus and Sour orange are B-inefficient genotypic rootstocks. In addition, Trifoliate orange was the moderate B-efficient rootstocks of five genotypes. The root-to-shoot dry mass ratio (R/S) and longer root numbers were higher in the Carrizo citrange and Red tangerine than that of Trifoliate orange, Fragrant citrus and Sour orange genotypes. That is to say, maintaining higher R/S and numerous longer lateral roots is very important in improving the B-efficiency and thus contribute much to the resistance of seedlings to B-deficiency in the Carrizo citrange and Red tangerine genotypes.     

The influence of arbuscular mycorrhizal colonisation on key growth parameters and fruit yield of pepper plants grown at high salinity

This study investigated the effects of arbuscular mycorrhizal (AM) colonisation by Glomus clarum on growth and fruit yield of pepper (Capsicum annum cv. 11B 14) grown at high salinity. The experiment was conducted in pots containing a mixture of perlite and sand (1:1, v/v) under glasshouse conditions. Treatments were: (1) no added NaCl without arbuscular mycorrhizae (NS-AM), (2) no added NaCl with arbuscular mycorrhizae (NS + AM), (3) added 50 mM NaCl without arbuscular mycorrhizae (S1-AM) and (4) added 100 mM NaCl without arbuscular mycorrhizae (S2-AM), (5) added 50 mM NaCl with arbuscular mycorrhizae (S1 + AM) and (4) added 100 mM NaCl with arbuscular mycorrhizae (S2 + AM). The NaCl treatments reduced pepper shoot and root dry matter, and fruit yield compared with the non-saline treatments. The concentrations of N, P and K, in the leaves were significantly reduced by salinity stress, however, mycorrhizal colonisation of the salt-stressed plants restored leaf nutrient concentrations to the levels in non-stressed plants in most cases. AM inoculation improved pepper growth under salt or saltless conditions and reduced cell membrane leakage.     

Integration of soil solarization and chemical sterilization with beneficial microorganisms for the control of white root rot and growth of nursery apple

White root rot (Dematophora necatrix (Mart.)) is a serious disease of apple (Malus domestica Borkh) in nurseries and orchards in India. In 2002 and 2003, field experiments were conducted to integrate soil solarization with native isolates of Azotobacter chrococcum and vesicular–arbuscular mycorrhizal fungi and observe its effect on the incidence of white root rot and growth of the saplings. Apple seeds coated with two native isolates of A. chrococcum (AZUHF₁ and AZUHF₂) were sown in plots inoculated with 4 native isolates of va-mycorrhiza, i.e. AMUHF₁ (Glomus fesiculatum), AMUHF₂ (Glomus macrocarpum), AMUHF₃ (Glomus mosseae) and AMUHF₄ (Gigaspora sp.) in 14 different combinations and these plots were solarized with transparent polyethylene mulch (25 μm thick) for 40 days in summer months. Soil solarization resulted around 9 °C higher temperature with average maximum temperature of 38–39 °C. Inoculation of saplings with AMUHF₁ isolate of va-mycorrhiza and AZUHF₁ isolate of A. chrococcum and then their planting in solarized soil was found most effective with no incidence of white root rot in comparison to 33.6–35.4% in control accompanied with 78–113% increase in shoot length and 81.6–84.3% increase in root length. Shoot and root length of the saplings was 9.6–10.6 and 9.2–16.0% higher, respectively, in solarized plots in comparison to sterilized plots.     

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.     

Selection of arbuscular mycorrhizal fungi for citrus growth promotion and Phytophthora suppression

In order to reduce unnecessary amount of P-fertilizer and severity of Phytophthora root rot in citrus orchards, the experiment was set up. Thirteen indigenous arbuscular mycorrhiza (AM) fungi species were isolated from rhizosphere soil of citrus orchards in Thailand and were then propagated into three host plants [sorghum (Sorghum bicolor), maize (Zea mays), and leek (Allium cepa)] by trap culture. We also tested whether indigenous AMF species (13 different species) could colonize into three cultivars of citrus scions and rootstocks (Shogun: Citrus reticulata Blanco cv. Shogun; Tangerine: C. reticulata; and C-35 citrange: Citrus sinensis × Poncirus trifoliata). With root colonization rates, the results indicated that Acaulospora tuberculata and Glomus etunicatum provided the best colonization in all citrus cultivars. We selected, therefore, those AMF species to verify their influences on citrus growth and Phytophthora root rot resistance. Three cultivars of citrus scions and rootstocks, Shogun, Tangerine and C-35 citrange, were inoculated with two effective indigenous AMF species, G. etunicatum or A. tuberculata in order to determine the influences on citrus growth. The plants were investigated to determine the mycorrhizal efficiency index (MEI), AM colonization, P content, and other parameters. Co-inoculation of AMF species (G. etunicatum or A. tuberculata) with Phytophthora nicotianae was also carried out in Shogun scion/C-35 citrange rootstocks. The results of citrus growth revealed that Shogun and Tangerine inoculated with G. etunicatum produced the highest MEI. Tangerine and C-35 citrange amended with fertilizers and G. etunicatum showed the highest P content in leaves. This indicated that G. etunicatum has an influence on citrus growth and P uptake, suggesting it to be the highly effective strain. Shogun scion/C-35 citrange rootstock combinations that were inoculated by both P. nicotianae and different AM fungi (G. etunicatum or A. tuberculata) showed root injury at low level of root rot symptom. However, the part of Shogun scions grafted on rootstocks showed severe symptom of shoot die back in treatment inoculated with P. nicotianae alone, while treatment inoculated with different AM species (G. etunicatum or A. tuberculata) and P. nicotianae rendered lower shoot die back symptoms than that of Phytophthora treatment. The low level of shoot die back symptom was shown at first, then healthy young shoot was restored. Our results indicated the facts that different host plants and different AMF species produced different outcomes of growth and pathogen resistance. The application of both AM isolates, therefore, has an enormous potential to be produced the inoculum for citrus orchards.     

Effect of arbuscular mycorrhizal fungi on growth,mineral nutrition,antioxidant enzymes activity and fruit yield of tomato grown under salinity stress

The purpose of this study was to investigate the mechanisms underlying alleviation of salt stress by arbuscular mycorrhizal fungi Glomus mosseae. Tomato (Lycopersicon esculentum L. cv. Zhongzha105) plants were cultivated in soil with 0, 50 and 100 mM NaCl. Mycorrhization alleviated salt induced reduction of root colonization, growth, leaf area, chlorophyll content, fruit fresh weight and fruit yield. The concentrations of P and K were higher in AM compared with nonAM plants grown under nonsaline and saline conditions. Na concentration was lower in AM than nonAM plants grown under nonsaline and saline conditions. AMF colonization was accompanied by an enhancement of activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in leaves of both salt-affected and control plants. In addition, inoculation with AMF caused reduction in MDA content in comparison to salinized plants, indicating lower oxidative damage in the colonized plants.     

Effects of low temperature storage on growth and transplant quality of non-grafted and grafted cantaloupe-type muskmelon seedlings

Grafting is a unique horticultural technology that allows the grower to select an alternate, compatible root system with natural disease resistance for their desired crop. Short-term storage of grafted seedlings under low temperature may extend the production window of grafted seedlings, reduce the labor input and increase production of grafted seedlings with a small propagation capacity. To evaluate the low temperature storage conditions, Cucumis melo ‘Olympic Gold’ seedlings were grafted onto Cucurbita maxima x Cucurbita moschata ‘Tetsukabuto’ rootstock and stored for a period of 2 or 4 weeks at 9, 12, or 15 °C under 12 μmol m⁻² s⁻¹ photosynthetic photon flux (PPF). The study demonstrated that grafted seedlings could be stored at 12 °C for 4 weeks without significant dry mass accumulation or effects on post-storage growth and development. Grafted seedlings stored at 15 °C for 4 weeks had a significant increase in dry mass and stem elongation; this was not observed for the non-grafted seedlings stored under the same conditions, suggesting that the rootstock enhanced the scion growth at lower temperatures than optimal for muskmelon. Storing muskmelon seedlings at 9 °C caused chilling damage but the damage was pronounced for non-grafted seedlings than grafted seedlings. ‘Tetsukabuto’ rootstock, an interspecific squash, presumably has a chilling tolerance and increased the storability of muskmelon seedlings. Further optimization is needed but there is potential for using this technique as a tool for mass production of grafted muskmelon seedlings.     

Effects of different mulches and irrigation methods on root growth,nutrient uptake,water-use efficiency and yield of strawberry

Field studies were conducted for two consecutive years under sub-temperate climatic conditions at Nauni in district Solan of Himachal Pradesh (30°52′N, 77°11′E 1175 asl) on loamy sand Inceptisols to investigate the effect of different mulches (hay: HM, black polyethylene: BP) on root growth, nutrient uptake, water-use efficiency (WUE) and yield of strawberry cv. Chandler under drip (DI) and surface irrigation (SI) systems. Unmulch (UM) and rainfed treatments were kept as control. Higher soil moisture content was registered under both the mulch materials during entire crop growth period. However, it was greater under BP mulch as compare to HM. The moisture conservation increased by 2.80–12.80% under BP mulch as compared to UM. HM treatment, irrespective of irrigation method increased the minimum soil temperature (2.8–5.2 °C) and reduced the maximum soil temperature (2.7–5.8 °C) as compared to UM. BP mulch increased the minimum soil temperature from 0.4 to 2.5 °C. Application of irrigation moderated the soil (minimum 2.6 and maximum 1.4 °C) temperature. Both the mulch materials were effective in enhancing root growth, nutrient uptake, WUE and yield. Application of mulch enhanced the root growth (63%), nutrient uptake (179.20%), WUE (84.40%) and yield (343%) under DI. However, respective increase under SI was 23.60, 83.80, 109.40 and 219.20%. Under DI, 51% of irrigation water was saved and about 19% higher fruit yield was obtained as compared with SI treatment. Linear regression model could significantly describe the variations in nutrient uptake (N, P and K) and WUE of strawberry under sub-temperate climatic conditions, root mass density was better indicator for estimating nutrient uptake of strawberry.     

Differences of hyphal and soil phosphatase activities in drought-stressed mycorrhizal trifoliate orange (Poncirus trifoliata) seedlings

Differences of hyphal and soil phosphatase activities between mycorrhizal and non-mycorrhizal plants were less studied under drought-stressed (DS) conditions. In a pot experiment, fungal alkaline phosphatase (FALP), and succinate dehydrogenase (FSDH), soil phosphatase activity, both soil and plant P contents were compared in 6.5-month-old trifoliate orange (Poncirus trifoliata) seedlings under 80 days of DS with or without inoculations by arbuscular mycorrhizal fungi (AMF, Glomus diaphanum, Glomus mosseae or Glomus versiforme). Plant growth and biomass production under DS were significantly higher in mycorrhizal than in non-mycorrhizal seedlings. Both the FALP and the FSDH activities under DS were significantly reduced in these three Glomus inoculated seedlings. In general, similar soil neutral and alkaline phosphatase activities, but significantly higher soil acid and total phosphatase activities, were exhibited in mycorrhizal than in non-mycorrhizal seedlings under both the well-watered (WW) and the DS. Both leaf and root P contents were significantly higher in the AM colonized seedlings, but soil available P contents were lower in the growth media with AM seedlings. Our results showed that higher hyphal enzymes’ activities, soil acid and total phosphatase activities, and plant P contents in AM colonized seedlings, particularly in Glomus mosseae-colonized seedlings and/or under DS, would result in a better growth of the host plants, which might be the basis for enhancing drought tolerance in plants.     

Nursery inoculation of tomato with arbuscular mycorrhizal fungi and subsequent performance under irrigation with saline water

Protected horticultural crops as well as those planted in open fields particularly in the Mediterranean region have to cope with increasing salinization of irrigation water. High salinity of the supply water has detrimental effects on soil fertility and plant nutrition and reduces crop growth and yield. This study was conducted to determine if pre-inoculation of transplants with arbuscular mycorrhizal (AM) fungi alleviates salt effects on growth and yield of tomato (Lycopersicon esculentum Mill. Cv. Marriha) when irrigated with saline water. Tomato seeds were sown in polystyrene trays with 20 cm³ cells and treated with AM fungi (AM) or without (nonAM) Glomus mosseae. Once the seedlings were reached appropriate size, they were transplanted into nonsterile soil in concrete blocks (1.6 m × 3 m × 0.75 m) under greenhouse conditions. The soil electrical conductivity (EC_e) was 1.4 dS m⁻¹. Plants were irrigated with nonsaline water (EC_w = 0.5 dS m⁻¹) or saline water (EC_w = 2.4 dS m⁻¹) until harvest. These treatments resulted with soil EC at harvest 1.7 and 4.4 dS m⁻¹ for nonsaline and saline water treatments, respectively. Root colonization with AM fungi at flowering was lower under saline than nonsaline conditions. Pre-inoculated tomato plants with AM fungi irrigated with both saline and nonsaline water had greater shoot and root dry matter (DM) yield and fruit fresh yield than nonAM plants. The enhancement in fruit fresh yield due to AM fungi inoculation was 29% under nonsaline and 60% under saline water conditions. Shoot contents of P, K, Zn, Cu, and Fe were higher in AM compared with nonAM plants grown under nonsaline and saline water conditions. Shoot Na concentrations were lower in AM than nonAM plants grown under saline water conditions. Results indicate that pre-inoculation of tomato transplants with AM fungi improved yield and can help alleviate deleterious effects of salt stress on crop yield.     

丛枝菌根真菌对水分胁迫下枇杷实生苗生长和养分吸收的影响

 以‘早钟6号’枇杷（Eriobotrya japonica Lindl.‘Zaozhong 6’）实生苗为试材,研究了3种水分梯度（正常供水、轻度水分胁迫和重度水分胁迫）下,分别接种3种丛枝菌根（arbuscular mycorrhiza,AM）真菌（光壁无梗囊霉Acaulospora laevis、摩西球囊霉Glomus mosseae和苏格兰球囊霉Glomus caledonium）对实生苗生长和养分吸收的影响。结果表明,接种AM真菌的植株具有更高的地上部和地下部干质量;3种AM真菌均可增加枇杷苗氮、钾、磷、钙、镁、铜的吸收。说明接种AM真菌增强了枇杷苗的养分吸收能力,提高了其抗旱性,促进了枇杷苗生长。在3种AM真菌中苏格兰球囊霉是枇杷苗的优势菌种。     

Screening of AM fungi and Azotobacter chroococcum under natural,solarization, chemical sterilization and moisture conservation practices for commercial mango nursery production in north-west Himalayas

The present study investigates the performance of mango seedlings screened with indigenous arbuscular mycorrhizal (AM) fungi and Azotobacter chroococcum strains under solarized, chemical sterilized and natural soil conditions. Two isolates each of AM fungi namely, Glomus fasciculatum (Thaxter sensu Gerdemann) and Glomus mosseae (Nicol. & Gerd.), and two strains of A. chroococcum viz., A. chroococcum strain-I (AZ1) and A. chroococcum strain-II (AZ2) were inoculated at nursery stage under four different moisture conservation practices viz., black polyethylene mulch and organic mulches (grass mulch, cover crops, green manure) and clean cultivation. The observations on microbial population, root colonization, growth parameters and leaf nutrient content of the seedlings were recorded. Mango seedling's inoculated with G. fasciculatum and AZ1 had increased seedling's height, diameter, leaf area and total root length, microbial consortium of the rhizosphere soil and leaf N, P, K and Zn content in plots where solarization and black polyethylene mulching was used. The study revealed that the inoculation of mango stones and the saplings with G. fasciculatum and AZ1 under solarized black polyethylene mulched practice may be considered the best practice for raising mango nursery and maintaining soil health under rain-fed conditions of mid-hills of north-west Himalayas.     

The influence of irrigation system and nutrient solution concentration on potted geranium production under various conditions of radiation and temperature

Zonal geranium (Pelargonium × hortorum ‘Real Mintaka’) were grown in closed soilless systems to evaluate the effects of irrigation system (drip and subirrigation) and nutrient solution concentration (half and full) under various conditions of radiation and temperature (winter and summer) in terms of substrate electrical conductivity (EC_s), growth, quality, crop evapotranspiration (ET_c) and growth index water use efficiency (WUE_GI) and nutrient uptake. At he end of the cultural cycle the highest EC_s in the upper and lower layers were recorded in the spring season on plants grown in subirrigation using a full nutrient solution concentration. The highest shoot biomass, leaf area, plant growth index, and quality index were recorded in the winter season on plants grown in both drip-irrigation and subirrigation using half and full nutrient solution concentration, whereas the lowest value was observed in the spring season on plants grown with subirrigation using the full nutrient solution concentration. The highest maximum air temperature recorded during the first 20 days after transplanting in the spring growing season was presumably responsible for the reduction in shoot biomass production, growth and quality index, and in time of geranium flowering compared to the plants grown in the winter season. The ET_c was 44% higher in spring than in winter season treatment, while the effect of the irrigation system was less pronounced with an increase in 11% in the subirrigation treatment compared with the drip-irrigation system. WUE_GI was not stable and showed a seasonal variability. Solar radiaton (R_s), air temperature (T_a) and vapour pressure deficit (VPD) were greatly higher in the spring season, which influenced WUE_GI negatively. The WUE_GI improved especially when R_s, T_a and VPD were below 12 MJ m², 20 °C and 0.6 kPa, respectively. The highest N, and Mg uptake were recorded in the winter season, especially on plants grown with subirrigation at 2 dS m⁻¹. The highest P, K, and Ca uptake values were measured during winter season using subirrigation system, and on plants grown under full strength nutrient solution. The variation of the nitrate concentration and EC in the nutrient solution during the spring growing cycle was less pronounced in the subirrigation than with a drip-irrigation system which represents an important aspect for the simplification of the closed loop management of the nutrient solution.     

Growth and nutrient partitioning of containerized Cercis siliquastrum L. under two fertilizer regimes

Lebanon's native flora is threatened by loss of natural habitat to rural and urban development and the increased demand of plant materials for landscaping. Despite Lebanon's floristic richness, most taxa used for landscaping are non-native. This study was done to determine if Cercis siliquastrum (L.) is amenable to container production. Therefore, six open pollinated seeds sources native to Lebanon were grown under two fertilizer rates to study growth, N, P, K uptake efficiency, and partitioning. Two-year-old seedlings were planted in 11 L containers in a 3:1 pine bark:compost substrate. Seedlings within each seed source or mother tree were grown at either 25 or 100 mg N L⁻¹ from 21N–3.1P–5.9K water-soluble fertilizer. Seedlings of all sources grown under 25 mg N L⁻¹ had greater dry weight than those grown at 100 mg. Nutrient loading occurred in plants under the high fertilizer rate, although total plant N, P, and K content were not affected by fertilizer rate. There were significant differences in mineral nutrient uptake and nutrient use efficiencies among the seed sources. The results show that C. siliquastrum is amenable to container production. The great variation in growth rate and nutrient use efficiency among the limited number of seed sources studied suggest that significant improvement can be made through mother tree selection and/or clonal propagation of superior individual plants within a source.     

Growth and development of Lilium longiflorum ‘Nellie White’ during bulb production under controlled environments : II. Effects of shifting day/night temperature regimes on scale bulblets

One-year old scale bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown for 107 days during growth period 1 (GP-1) in six growth chambers under constant day/night temperature regimes of 30/26, 26/22, 22/18, 18/14, 14/10 and 10/6 °C. Subsequently, half of the plants in each temperature regime were transferred to 18/14 °C and the other half continued at the six constant temperature regimes. Both groups of plants were grown for an additional 89 days in growth period 2 (GP-2). Continuous temperatures of 26/22, 26/22–22/18 and 26/22–18/14 °C produced the greatest increase in basal bulb fresh weight (the main planted bulb), basal bulb circumference and stem bulb fresh weight, respectively. However, shifting these optimal temperatures to 18/14 °C during GP-2 resulted in a lower increase in basal bulb fresh weight and circumference. The optimum range for stem bulb production was expanded to 30/26–14/10 °C by shifting to 18/14 °C. The greatest increase for basal root growth occurred at 14/10–10/6 °C and for stem root growth at 14/10 °C. The temperature shift did not affect either root type. Maximum increase for stem length was at 26/22 and 22/18 °C and for stem plus leaf weight at 14/10 °C under constant temperature regimes. Transferring the plants from 10/6 to 18/14 °C resulted in the greatest increase in stem length and from 10/6 and 14/10 to 18/14 °C in the greatest increase in stem plus leaf weight. The greatest increase in the number of leaves occurred at 26/22 and 10/6 °C, but this growth parameter was unaffected by shifting to 18/14 °C, indicating that leaf number was determined in GP-1. Bulbils developed only when bulbs at high GP-1 temperature regimes (30/26 and 26/22 °C) were transferred to 18/14 °C during GP-2. Lower temperatures tended to favor an increase in flower bud production under continuous temperature regimes, while shifting to 18/14 °C increased flower bud production after initially high and low temperatures. Meristem abortion was greatest at 30/26 °C followed by 26/22 °C, but was not affected by temperature shifts in GP- 2. Thus, it is concluded that the abortion was induced or initiated during GP-1.     

Prolonged high-temperature exposure differentially reduces growth and flowering of 12 Viola × wittrockiana Gams. cvs

Many cool season garden crops, including Viola × wittrockiana Gams. (pansy), exhibit reduced flowering outdoors during the warm summer months. Twelve pansy cultivars varying in summer garden performance were grown under either 20 ± 1.5 or 30 ± 1 °C (air temperature) to determine growth and flowering responses to prolonged high-temperature exposure and to identify selection criteria to screen pansies for flowering heat tolerance. Increasing temperature from 20 to 30 °C increased leaf number below the first flower on ‘Crystal Bowl Primrose’ and ‘Skyline White’ only. Flower bud number reduction at 30 °C versus 20 °C varied from 20% for ‘Crystal Bowl Purple’ to 77% for ‘Majestic Giants Red and Yellow’. Flower diameter reduction at 30 °C versus 20 °C ranged from 14% for ‘Skyline Beaconsfield’ to 44% for ‘Super Majestic Giants Ocean’. The percentage reduction in total color (flower number × estimated flower area) ranged from 60% for ‘Crystal Bowl Primrose’ to 88% for ‘Majestic Giants Rose Shades’. Based on a weighted base selection index, ‘Super Majestic Giants Canary’ and ‘Delta Yellow’ were identified as the most heat-tolerant cultivars, while ‘Super Majestic Giants Ocean’ and ‘Majestic Giants Rose Shades’ were identified as the most heat-sensitive. In a second experiment, root and shoot dry mass were determined after 10, 20, or 30 d when grown at 20 or 30 °C. Relative growth rate and root:shoot ratio were also calculated. After 30 d, ‘Crystal Bowl Primrose’, ‘Crystal Bowl Sky Blue’ and ‘Skyline White’ relative growth rates were lower at 30 °C versus 20 °C. Root:shoot ratio on day 30 was lower at 30 °C compared to 20 °C for six cultivars, but similar across temperature for five cultivars and higher for ‘Crystal Bowl Primrose’. Flower bud number at first flower was positively correlated with branch number, shoot dry mass at flowering, but not correlated with root dry mass at flowering, and negatively correlated with flower diameter and root:shoot ratio (either at flowering, or after 10, 20 or 30 d at 30 °C), suggesting that these traits may be useful when screening pansies for flowering heat tolerance.     

Chloride and sodium excluding capacities of citrus rootstock germplasm introduced to Australia from the People's Republic of China

The responses to root zone salinity (0, 25 and 50 mM NaCl) by 40 citrus rootstock genotypes introduced from the People's Republic of China, measured as shoot chloride (Cl⁻) and sodium (Na⁺) ion accumulation, growth and dry matter accumulation, were investigated under glasshouse conditions. Two experiments, one using aerated nutrient solutions and the other irrigated sand cultures, were conducted with plants grown from rooted cuttings taken from representative trees of different mandarin (Citrus reticulata Blanco and C. erythrosa Hort. ex Tan.), yuzu (C. junos Sieb. ex Tan.), Ichang papeda (C. ichangensis Swing.), sour orange (C. aurantium L.) and trifoliate orange (Poncirus trifoliata (L.) Raf.) genotypes. Two standard genotypes, viz. Rangpur lime (Citrus x limonia Osbeck.) and William's trifoliate orange were included in the experiments as reference controls.     

Addition of salicylic acid to nutrient solution combined with postharvest treatments (hot water,salicylic acid,and calcium dipping) improved postharvest fruit quality of strawberry

This experiment was conducted to study the effect of salicylic acid addition to nutrient solution and different postharvest treatments on fruit quality of strawberry cv. Camarosa after 7 days at 2 °C. Plants were irrigated with two complete nutrient solutions, with salicylic acid (0.03 mM) or without salicylic acid as the control. Fruits were then treated with eight different postharvest treatments (25 °C water, 45 °C water, 25 °C or 45 °C water containing CaCl₂ (1%), 25 °C or 45 °C water containing salicylic acid (2 mM) and 25 °C or 45 °C water containing both CaCl₂ (1%) and salicylic acid (2 mM)). Fruits which received SA in their nutrient solution had less weight loss and decay and higher firmness. All of the postharvest treatments improved fruit quality characteristics. Fruits dipped in salicylic acid solution had less weight loss, decay and a* (redness) and higher firmness and hue angle than control. Heat treated fruits had less decay and a* and higher hue angle than control. Fruits dipped in CaCl₂ solution had less weight loss, decay and a* and higher firmness than control. Combination of the three postharvest treatments improved firmness, decay, weight loss and vitamin C.     

Effect of low temperature on breaking dormancy and flowering of Arisaema sikokianum (Araceae)

Arisaema sikokianum (Araceae) native to Japan is classified as a vulnerable species in the Red Data Book of Japan. Control of dormancy is essential for efficient corm production and forcing culture. Sprouting of both vegetative and reproductive corms was enhanced by exposure to low temperature. Vegetative corms exposed to low temperatures at 5 °C longer sprouted faster when grown at 20 °C. Effective temperatures for breaking dormancy was 5 °C. Reproductive corms treated at 5 °C longer showed shorter days to flower. Successful forcing culture was achieved; corms treated at 5 °C from November for 30 days flowered on 5th February.     

Screening mycorrhiza species for plant growth,P and Zn uptake in pepper seedling grown under greenhouse conditions

We screened the mycorrhizal species for an inoculum protocol would green pepper seedling production and compensate for nutrient deficiency. Three greenhouse studies (on three successive years) were conducted under nursery conditions using five arbuscular mycorrhizal (AM) fungi and their mixture. The AM fungi, Glomus mosseae, G. clarum, G. caledonium, G. intraradices and G. etunicatum propagated on maize roots were used. The AM fungi were inoculated to seed stages and half of the seed stages inoculated plants were re-inoculated at the seedling stages. In Experiment I, plants were harvested once and in Experiments II and III, plants were harvested twice at different developmental stages.