Life cycle and growth ofPotamogeton crispus L. in a shallow pond,ojaga-ike

The life cycle and growth ofPotamogeton crispus L. were studied in a shallow pond, Ojaga-ike. With respect to the shoot elongation and seed and turion formations, the life cycle of this plant in the pond could be divided into following five stages: germination, inactive growth, active growth, reproductive and dormant stages. It was suggested that the plant showed these successive stages depending mainly upon water temperature. The turions germinated on the bottom in autumn when the water temperature fell below ca. 20 C. The plant showed hardly any growth during winter (December—early March) when the temperature was below 10 C. In the spring when the bottom water temperature rose to above 10 C (mid-March), the plant started to grow again and the shoot elongated rapidly at the rate of 4.2 cm day⁻¹ until the shoot apex reached the pond surface in late April. Both the increment of node number and the internodal elongation were associated with this rapid shoot growth. On 10 May (last sampling date), the mean values of shoot length, internodal length and the number of nodes estimated for 10 predominant plants were 238.2±5.6 cm, 7.1±0.8 cm and 34.9±4.0 cm, respectively. The turion formation and flowering occurred during the period from mid-April to mid-May when the surface water temperature ranged 19 and 22 C. The dry weight of a plant reached the maximum mean value of 1180 mg on 10 May. At its peak biomass, an individual plant produced 1–10 turions (5.5 on average) of which the mean individual turion dry weight was 53.2 mg. The turion dry weight accounted for ca. 42% of the total plant biomass m⁻² at that time.     

Pollen-Specific Expression of <Emphasis Type="Italic">Oryza sativa Indica</Emphasis> Pollen Allergen Gene (<Emphasis Type="Italic">OSIPA</Emphasis>) Promoter in Rice and <Emphasis Type="Italic">Arabidopsis</Emphasis> Transgenic Systems

Earlier, a pollen-specific Oryza sativa indica pollen allergen gene (OSIPA), coding for expansins/pollen allergens, was isolated from rice, and its promoter—upon expression in tobacco and Arabidopsis—was found active during the late stages of pollen development. In this investigation, to analyze the effects of different putative regulatory motifs of OSIPA promoter, a series of 5′ deletions were fused to β-glucuronidase gene (GUS) which were stably introduced into rice and Arabidopsis. Histochemical GUS analysis of the transgenic plants revealed that a 1631 bp promoter fragment mediates maximum GUS expression at different stages of anther/pollen development. Promoter deletions to −1272, −966, −617, and −199 bp did not change the expression profile of the pollen specificity. However, the activity of promoter was reduced as the length of promoter decreased. The region between −1567 and −199 bp was found adequate to confer pollen-specific expression in both rice and Arabidopsis systems. An approximate 4-fold increase in the GUS activity was observed in the pollen of rice when compared to that of Arabidopsis. As such, the OSIPA promoter seems promising for generation of stable male-sterile lines required for the production of hybrids in rice and other crop plants.     

In vitro propagation of the endangered plant <Emphasis Type="Italic">Centaurea ultreiae</Emphasis>: assessment of genetic stability by cytological studies,flow cytometry and RAPD analysis

The effect of different cytokinins on multiple shoot regeneration from shoots of Centaurea ultreiae was studied. The culture system consisted of solid basal half-strength Murashige and Skoog medium supplemented with one of four cytokinins [6-benzyladenine (BA), zeatin, kinetin, or N⁶-(2-isopentyl) adenine (2-iP)] at each of five different concentrations. The highest multiplication rate (5.52 shoots per explant) was obtained in the medium supplemented with 4.44 μM BA. Shoots were successfully rooted (91% success) by dipping the basal end into a solution containing 10 M 1-naphthaleneacetic acid for 30 s. Genetic stability of the regenerated plants was assessed by random amplified polymorphic DNA (RAPD) analysis and flow cytometry. In the initial randomly selected plant material (control) and 20 of its regenerants, 2,688 bands were generated by RAPD with 12 different primers, and the same banding profiles were exhibited. Molecular and cytological analyses did not reveal genomic alterations in any of the regenerated plants obtained on medium containing 4.44 μM BA. The success of acclimatization to environmental conditions—100% of plants were successfully acclimatized—suggests that the micropropagation system described is a reliable method for propagation of C. ultreiae.     

The influence of waterlogging at different temperatures on penetration depth and porosity of roots and on stomatal diffusive resistance of pea and maize seedlings

The 8 days old seedlings of pea (cv. Ilowiecki) and maize (cv. Alma F1) were subjected to differentiated aeration conditions (control — with pore water tension about 15 kPa and flooded treatment) for 12 days at three soil temperatures (7, 15 and 25 °C). The shoots were grown at 25 °C while the soil temperature was differentiated by keeping the cylinders with the soil in thermostated water bath of the appropriate temperature. Lowering the root temperature with respect to the shoot temperature caused under control (oxic) conditions a decrease of the root penetration depth, their mass and porosity as well as a decrease of shoot height, their mass and chlorophyll content; the changes being more pronounced in maize as compared to the pea plants. Flooding the soil diminished the effect of temperature on the investigated parameters; the temperature effect remaining significant only in the case of shoot biomass and root porosity of pea plants. Root porosity of pea plants ranged from 2 to 4 % and that of maize plants — from 4 to 6 % of the root volume. Flooding the soil caused an increase in the root porosity of the pea plants in the entire temperature range and in maize roots at lower temperatures by about 1 % of the root volume. Flooding the soil caused a decrease of root mass and penetration depth as well as a decrease of plant height, biomass and leaf chlorophyll content.     

Plant frequency,stem and root characteristics,and CO<Subscript>2</Subscript> uptake for <Emphasis Type="Italic">Opuntia acanthocarpa</Emphasis>: elevational correlates in the northwestern Sonoran Desert

A common cylindropuntia in the northwestern Sonoran Desert, Opuntia acanthocarpa, was investigated for the following hypotheses: its lower elevational limit is set by high temperatures, so its seedlings require nurse plants; its upper elevational limit is set by freezing; spine shading is the least at intermediate elevations; and changes in plant size and frequency with elevation reflect net CO₂ uptake ability. For four elevations ranging from 230 m to 1,050 m, the mean height of O. acanthocarpa approximately doubled and its frequency increased 14-fold. Nurse plants were associated with only 4% of O. acanthocarpa less than 20 cm tall at the two lower elevations compared with 57% at 1,050 m, where putative freezing damage was especially noticeable, suggesting that nurse plants protect from low temperature damage. Spine shading of the stem doubled from the lowest to the highest elevation. Net CO₂ uptake, which followed a Crassulacean acid metabolism pattern, was maximal at day/night air temperatures of 25/15°C and was halved by 4 weeks of drought and by reducing the photosynthetic photon flux from 30 to 12 mol m^-2 day^-1. The root system of O. acanthocarpa was shallow, with a mean depth of only 9 cm for the largest plants. Root growth was substantial and similar for plants at 25/15°C and 35/25°C, decreasing over 70-fold at 15/5°C and 45/35°C. Based on cellular uptake of the vital stain neutral red, neither roots nor stems tolerated tissue temperatures below -5°C for 1 h while both showed substantial high temperature acclimation, roots tolerating 1 h at 61°C and stems 1 h at 70°C for plants grown at 35/25°C. The increase in height and frequency of O. acanthocarpa with elevation apparently reflected both a greater ability for net CO₂ uptake and greater root growth and hence water uptake. This species achieves its greatest ecological success at elevations where it becomes vulnerable to low temperature damage.     

<Emphasis Type="Italic">In vitro</Emphasis> micropropagation of three rare,endangered, and endemic rhododendron species of Northeast India

In vitro propagation of three rare, endangered and endemic rhododendron species—Rhododendron dalhousiae var. rhabdotum, R. elliottii, and R. johnstoneanum—was attained. Nodal explants were used for multiple shoot induction studies. Three cytokinins (isopentenyladenine, benzyladenine, and kinetin) were evaluated in all three species. Isopentenyladenine performed better in all three species, especially at the concentration of 39.36 μM. Testing of combinations of growth regulators revealed that explants grown on Anderson medium supplemented with 39.36 μM isopentenyladenine and 4.90 μM indole butyric acid gave optimum results with 100% multiple shoot induction, 18 shoots per explant, and shoot length of 2.07 cm with R. johnstoneanum. Indole butyric acid was found to be the best auxin for root formation. Around 60% of the in vitro-raised plants of R. elliottii, R. johnstoneanum, and R. dalhousiae var. rhabdotum were able to establish ex vitro.     

<Emphasis Type="Italic">Drepanocladus longifolius</Emphasis> (Amblystegiaceae), an addition to the moss flora of King George Island,South Shetland Islands,with a review of Antarctic benthic mosses

Drepanocladus longifolius (Mitt.) Paris is recorded for the first time from King George Island, South Shetland Islands, in the maritime Antarctic. It was collected in West Lake during the 23rd Chinese National Antarctic Research Expedition in 2006–2007. The moss was found at a depth of 5–6 m attached to the bed of the lake. The stems of the moss are about 1–1.5 m in length. The moss exhibits seasonal growth patterns, with shorter branch internodes, more widely spaced leaves and more branches in summer than in winter. Most of the branches are initiated in summer. The annual shoot extension is about 3–6 cm, which implies that the plants must be at least 15 years of age. The distribution of aquatic moss species and records in Antarctica is outlined and discussed and the nomenclature of previous reports clarified.     

The effects of biochars produced in different pyrolsis temperatures from agricultural wastes on cadmium uptake of tobacco plant

Abiotic stresses caused by cadmium (Cd) contamination in soil retard plant growth and decline the quality of food. Amendment of biochar was reported effective in reduction of mobility, plant uptake and toxicity of Cd in plants. The aim of this study was to investigate the effect of biochar applications produced from corn cob and rice husk at three different pyrolysis temperatures (400, 500 and 600 °C) on Cd uptake of tobacco plants. The results showed that the shoot Cd concentration and content of tobacco plants significantly increased with the application of Cd in increasing doses. The results showed that increasing Cd dosescaused significant increase (P < 0.01) in shoot Cd concentration and content of the tobacco plant at three different pyrolysis temperatures of both corn cob and rice husk biochars. The concentration of Cd was 0.48 mg kg^?1 in Cd0 dose of corn cob biochar produced at 500 °C and increased to 61.6 mg kg^?1 at Cd5, while Cd concentration increased to 72.3 mg kg^?1 with rice husk biochar. Despite the increase in Cd concentrations and content, shoot Cd concentrations and contents were significantly (P < 0.01) reduced with the treatments of corn cob and rice husk biochars produced at different pyrolysis temperatures. The Cd concentration at Cd5 dose in the absence of biochar addition was 90.5 mg kg^?1, while Cd concentration at Cd5 dose in 400, 500 and 600 °C treatments of corn cob biochar was reduced to 66.5, 61.6 and 67.3 mg kg^?1 respectively, and to 77.0, 72.3 and 70.2 mg kg^?1 in rice husk biochar. The results also revealed that corn cob biochar treatments were more effective in reducing Cd uptake of tobacco plants compared to rice husk biochar. Higher specific surface area of corncob biochar compared to rice husk biochar caused to the difference between two biochar sources on Cd uptake of tobacco plants.     

Effects of Low Temperature on Growth and Nutrient Accumulation in Rye (Secale cereale) and Wheat (Triticum aestivum)

Rye (Secale cereale cv. Rheidol) and wheat (Triticum aestivumcv. Mardler) were grown at shoot/root temperatures of 20/20°C (warm grown, WG plants), 8/8 °C (cold grown, CG plants)and 20/8 °C (differential grown, DG plants). Plants fromcontrasting growth temperature regimes were standardized andcompared using a developmental timescale based on accumulatedthermal time (°C d) at the shoot meristem. Accumulationof dry matter, nitrogen and potassium were exponential overthe time period studied (150–550 °C d). In rye, therates of plant dry matter and f. wt accumulation were linearlyrelated to the temperature of the shoot meristem. However, inwheat, although the rates of plant dry matter and f. wt accumulationwere temperature dependent, the linear relationship with shootmeristem temperature was weaker than in rye. The shoot/rootratio of rye was stable irrespective of growth temperature treatment,but the shoot/root ratio of wheat varied with growth temperaturetreatment. The shoot/root ratio of DG wheat was 50% greaterthan WG wheat. In both cereals, nutrient concentrations anddry matter content tended to be greater in organs exposed directlyto low temperatures. The mean specific absorption rates of nutrientswere calculated for the whole period studied for each species/temperaturecombination and were positively correlated with both plant shoot/rootratio and relative growth rate. The data suggest that nutrientuptake rates were influenced primarily by plant demand, withno indication of specific nutrient limitations at low temperatures. Nutrient accumulation, relative growth rate (RGR), rye, Secale cereale cv. Rheidol, temperature, thermal time, Triticum aestivum cv. Mardler, wheat     

<Emphasis Type="Italic">In vitro</Emphasis> germination and micropropagation of <Emphasis Type="Italic">Givotia rottleriformis</Emphasis> Griff.

The propagation of Givotia rottleriformis Griff. is difficult as a result of long seed dormancy associated with poor seed germination. The present study was undertaken to develop a protocol to overcome seed dormancy by culture of zygotic embryo axes and then develop an efficient method for micropropagation of Givotia. Best germination frequency (78.3%) was achieved from mature zygotic embryo axes isolated from acid-scarified fresh seeds when cultured on Murashige and Skoog (MS) medium (half-strength major salts) with 28.9 μM gibberellic acid (GA₃). Efficient plant conversion was achieved by transfer of 10-d-old germinated embryos to MS medium (half-strength major salts) supplemented with 1.2 μM kinetin (KN) and 0.5 μM indole-3-butyric acid (IBA). However, acid scarification of 1-yr-old seeds decreased the germination frequency of zygotic embryo axes in comparison to those obtained from non-acid-scarified seeds which germinated (96.2%) and converted into plants (80.3%) on MS basal (half-strength major salts) medium. Multiple shoot bud induction was achieved by culture of shoot tips derived from in vitro germinated seedlings on MS medium with 0.5 μM thidiazuron for 4 wk, and the shoots elongated after transfer to a secondary medium with 1.2 μM KN. A maximum number of 7.8 shoots per explant with an average shoot length of 3.2 cm was achieved after two subcultures on this medium. The in vitro regenerated shoots rooted (41.5%) on half-strength MS medium with 0.5 μM IBA. The in vitro generated seedlings and micropropagated plants were established in soil with a survival frequency of 70% and 60%, respectively.     

Effects of Low Temperature on the Development and Morphology of Rye (Secale cereale) and Wheat (Triticum aestivum)

Seedlings of Secale cereale cv. Rheidol and Triticum aestivumcv. Mardler were grown at shoot/root temperatures of 20/20 °C,20/8 °C and 8/8 °C. During vegetative growth both cerealsproduced leaves, tillers and roots in a defined pattern, ata species-specific rate which was linearly related to the temperatureof the shoot meristem. Thus, plant development could be standardizedon a temperature x time (°C d) basis despite contrastinggrowth-temperature treatments. When compared at a similar developmentalstage, the cooling of whole plants or of plant roots resultedin an increase in the d. wt: f. wt ratio of both shoot and roottissues, a decrease in the length of both the longest shootand root, and the development of broader and thicker leaves.Although the effects of temperature on developmental characteristicscould be accurately predicted by an empirical relationship,the effects on morphological characteristics could not. Development, phyllochron, rye, Secale cereale cv. Rheidol, temperature, thermal time, Triticum aestivum cv. Mardler, wheat     

Visual Active Space of the Milfoil Weevil, <Emphasis Type="Italic">Euhrychiopsis lecontei</Emphasis> Dietz (Coleoptera: Curculionidae)

Euhrychiopsis lecontei Dietz (Coleoptera: Curculionidae), a native weevil, is used as a biological control agent for the invasive aquatic macrophyte, Eurasian watermilfoil (Myriophyllum spicatum L.). Because E. lecontei overwinters on land in the adult stage and must find plants in lakes each spring, plant finding behaviors are essential to eventually understanding and predicting long term biological control. Our research showed that E. lecontei is visually attracted to M. spicatum at up to 17.5 cm, and is more attracted to plants than other visual stimuli within 15 cm. We also showed that turbidity may affect visual plant finding at 15 cm. Using available data from this and other previous studies involving chemical cues and other life history traits, we propose a testable conceptual model for how E. lecontei finds plants each year, especially while underwater. This model may also be used to explain plant finding by aquatic phytophagous insects in general.     

Micropropagation of the endangered Chilean tree, <Emphasis Type="Italic">Gomortega keule</Emphasis>

The endangered tree Gomortega keule remains only in small, isolated populations surrounded by timber plantations in the biodiversity hotspot of central Chile. This species, belonging to the monotypic family Gomortegaceae, produces edible fruit and high-quality wood, but its difficult propagation makes conservation essential. The percentage of seed germination is less than 40%, germination time exceeds 12 mo, and cuttings fail to root. These difficulties have stimulated efforts to explore in vitro approaches for propagation. Cultures were established from zygotic embryos; the optimum culture conditions for shoot proliferation were semi-solid Woody Plant Medium (WPM) with 20 g/l sucrose, 0.1 mg/l α-naphthaleneacetic acid and 1.0 mg/l 6-benzylaminopurine, at 18°C. Explants required about 12 mo in culture before stabilized growth resulted in consistent shoot production. Regenerated shoots excised from parental explants developed a normal morphology 1 mo after transfer to WPM with 2.0 g/l of activated charcoal, and lacking plant growth regulators. These normal shoots were rooted with a treatment of 7 d on WPM without activated charcoal, but containing 20 mg/l indole-3-butyric acid, followed by return to the same medium with 2.0 g/l activated charcoal, without growth regulators, for 1 mo. Regenerated plants were transferred to compost and covered with transparent plastic sleeves. The latter were opened gradually to decrease humidity and to establish plants under glasshouse conditions. There is an urgent requirement to extend this protocol to material collected from diverse sites and to introduce micropropagated specimens into the wild and living plant repositories to conserve this endangered species.     

Induction of acrosome reaction of spermatozoa in <Emphasis Type="Italic">Eriocheir sinensis</Emphasis> by low temperature

The effects of temperatures, durations of treatment, and derivations from spermatophores or spermaries on in vitro acrosome reaction of the spermatozoa in the Chinese mitten crab Eriocheir sinensis were investigated. The results showed that the different temperatures resulted in extremely significant differences (p < 0.01) in the time of beginning acrosome reaction, the time of the maximum percentage of acrosome reaction, and the maximum percentage of acrosome reaction of the spermatozoa from spermatophores; and the low temperature (−20, −80 °C and liquid nitrogen) induced acrosome reaction of more than 90% spermatozoa while 15 and 4 °C didn’t. Similar results occur in the spermatozoa, treated with −80 °C for 15 min, from spermaries but the time of beginning acrosome reaction and the time of the maximum percentage of acrosome reaction were obviously longer than those from spermatophores. In conclusion, low temperature can induce acrosome reaction, which is a novel and efficient operating method of inducing acrosome reaction; the spermatozoa might be affected physiologically to capacitate with chilling. The study may be beneficial to new understandings of mechanism of acrosome reaction and provide the foundational material for artificial fertilization and breeding of this crab and other commercial aquatic crustaceans.     

Micropropagation of <Emphasis Type="BoldItalic">Embelia ribes</Emphasis> Burm f. through proliferation of adult plant axillary shoots

Micropropagation of Embelia ribes was achieved through proliferation of axillary shoots obtained from mature plants. Nodal shoot segments, collected March–May, exhibited high-frequency (75%) shoot initiation when cultured on Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ) at 1.13 μM and indole-3-butyric acid (IBA) at 0.49 μM. Subculture of sprouted shoots from the original explants on medium containing TDZ (1.13 and 0.45 μM) during the first and second subcultures was found essential for further shoot proliferation, while inhibition of shoot elongation by TDZ could be overcome by transferring shoot cultures onto MS medium containing 6-benzylaminopurine (BAP; 11.10 μM) for the third subculture. Treating the explants with an antioxidant mixture of 568 μM ascorbic acid, 119 μM citric acid, and 307 μM glutathione prior to inoculation, coupled with subculture at 2-wk intervals onto fresh medium, both helped to reduce browning of the explants and facilitated production of five to six shoots/explant. MS medium supplemented with BAP (4.44 μM) and IBA (0.49 μM) induced shoot multiplication, producing five to six shoots/explant with a shoot length of 3 to 4 cm over a 4-wk culture period. Shoots of 3 to 4 cm in length exhibited 100% rooting within 4 wk after transfer to media containing half the nutrient salt concentration of MS medium with 3.69 μM IBA. Ex vitro rooting in the greenhouse from the in vitro shoots treated with 4.93 μM IBA for 30 min exhibited 95% rooting in soilrite™ medium in a 4-wk period. About 85% of micropropagated plants were established successfully in root trainers. Three-month-old, hardened plants could further be successfully established in the field. In 1 yr, by using the above protocol, 3,200 plants could be produced from a single shoot and 2,700 could be established in the field.     

Factors affecting <Emphasis Type="Italic">in vitro</Emphasis> propagation and field establishment of <Emphasis Type="Italic">Chlorophytum borivilianum</Emphasis>

The effect of plant growth regulators (PGRs), gelling agents, sucrose and heat shock on shoot multiplication, shoot growth, rooting and subsequent survival of Chlorophytum borivilianum Sant. et Fernand was evaluated. Benzyladenine (BA) was found to be better cytokinin over kinetin (KIN) for shoot multiplication. Sucrose concentrations from 116–290 mM in the basal medium (BM) promoted shoot multiplication. Heat shock (50 °C, 1 h) also promoted shoot multiplication at these sucrose concentrations on both BM medium and BM supplemented with 5.0 μM BA. Beneficial effect of sucrose was also observed on rooting of shoots on BM as well as BM supplemented with 5.0 μM indole-3-butyric acid (IBA). Phytagel as a gelling agent was found to be more effective for shoot proliferation and growth compared to agar. Amongst various soil mixtures tested, higher survival of plants was observed in soil containing Vermicompost. It was interesting to note that a maximum plant survival (> 95 %) was observed when plants were directly transferred to net-house (irradiance reduced to 50 % with green net, without humidity and temperature control) than poly-house (with humidity and temperature control). Random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) analysis of regenerated plants showed genetic similarity to mother plant.     

Sink-Regulation of Photosynthesis in Relation to Temperature in Sunflower and Rape

Stimulation of the rate of photosynthesis at 2·0 kPaO₂ in comparison with 21 kPa O₂ and carbohydrate accumulationover 4h were measured during exposure of sunflower (Helianthusannuus L.) and rape (Brassica napus L.), grown at 30 °Cand 13 °C, to temperatures between 7 °C and 35 °C.The effect of reducing source: sink ratio by shading on theresponse of photosynthetic rate to temperature was also determined.Stimulation of photosynthesis by 2·0 kPa O₂ in comparisonwith 21 kPa O₂ decreased over 4 h at cool temperatures in sunflowerplants grown at 30 °C but not in rape grown at 30 °C.Stimulation did not decrease over 4 h in plants grown at 13CC. Sucrose was the main carbohydrate accumulated over 4 h;its accumulation increased with decreasing temperature. Starchaccumulation either decreased or remained the same with decreasingtemperature. In plants grown at 30 °C more carbohydrateaccumulated between 8 °C and 21 °C in sunflower thanin rape, but more carbohydrate accumulated at 30 °C in rapethan in sunflower. In plants grown at 13 °C much less carbohydrateaccumulated between 13 °C and 23 °C than in plants grownat 30 °C. Photosynthetic rate in plants grown at 30 °Cexposed to between 20 °C and 35 °C over 32 h (14 h light-10h dark-8 h light), declined over 32 h at 20 °C and 25 °Cin sunflower and at 20 °C in rape. This fall over 32 h,especially at 20 °C in sunflower, was significantly reducedby shading the rest of the plant. Shading had little effecton photosynthetic rate above 25 °C. The work confirms thatlow temperature imposes a sink-limitation on photosynthesiswhich occurs at higher temperatures in sunflower than in rape.This limitation may be relieved by decreasing the source:sinkratio. Key words: Sunflower, rape, photosynthesis, carbohydrates, sink demand, temperature     

Thermosensitive genetic dwarfs of apple

The role of environment on the dwarfing (short internode) phenomenon of apple (Malus domestisca Borkh.) was investi gated and defined in controlled environmental chambers. Orchard-grown very dwarf, dwarf and semi-dwarf trees obtained by natural sibcrossing of spur-type cv. Golden Delicious and cv. Delicious, as well as standard cv. Golden Delicious, were propagated via in vitro techniques. Growth was rapid and none of the 4 types exhibited dwarf-like characteristics when grown at constant 27°C with 12, 14 or 16 h daylengths. Standard and very dwarf plants grew at nearly the same rate at constant 30°C, whereas growth nearly ceased on both types at constant 35°C after 7 days. Dwarf and very dwarf plants responded differently from standard and semi-dwarf plants when grown under alternating (ramped) night/day temperatures (15 or 20°C night ramped up to a daytime maximum over 8 h of 23, 28, 33 or 38°C, held for 2 h and then ramped down over 5 h to the night temperature). As the night/maximum day temperature differentia) increased from 0 to 23° under the ramping environments, growth of dwarf plants decreased markedly as compared to standard plants. When the same night/maximum day temperature differential occurred, the effect on decreasing shoot length was greater at the higher (20°C) night temperature. Increasing maximum day temperatures under the ramped environment also reduced leaf area plant^?1 but did not markedly affect leaf number, resulting in short internodes. When a period of constant temperature was followed by ramped temperatures or vice versa, the sequence of constant vs ramped environments made little difference in the final growth of the 4 plant types. The data point to high temperature as the major factor for causing dwarfing of the sensitive plant types. Increasing the differential between night and maximum day temperature resulted in short internode. dwarf plants with small leaves similar to orchard-grown dwarf trees.     

Direct adventitious shoot induction and plant regeneration of <Emphasis Type="Italic">Embelia ribes</Emphasis> Burm F.

An efficient micropropagation system via direct shoot organogenesis from hypocotyl segments of Embelia ribes Burm F. was developed. A high frequency (84%) of adventitious shoot induction was obtained on Murashige and Skoog (MS) medium supplemented with additives (283.85 μM ascorbic acid [AA], 118.96 μM citric acid [CA], 142.33 μM cysteine, and 684.22 μM glutamine) and 1.13 μM of thidiazuron (TDZ) after 4 weeks following culture. Further development of shoot primordia into well-grown shoots of 4–5 cm in length was achieved by sub-culturing explants along with shoot primordia on MS medium supplemented with 0.44 μM benzyl adenine (BA) and 0.49 μM indole butyric acid (IBA) for three sub-culture periods with an interval of 15 days between them. The highest shoot multiplication was obtained when explants were incubated on MS medium supplemented with 2.2 μM BA and 0.49 μM IBA in 4 weeks. All in vitro developed shoots, 3–4 cm in length, rooted when grown on half-strength MS basal medium along with 2.47 μM IBA within 4 weeks. Moreover, 100% of shoots developed roots when these were treated with 4.93 μM IBA for 20 min and then transferred to pots containing soilrite mix and grown in the greenhouse. In vitro and ex vitro rooted plants showed a survival of 85 and 95% respectively, during hardening in the greenhouse for a 6-week period.