Leaf Span Research Articles

Split X-Jaw techniques of volumetric modulated arc radiotherapy in nasopharyngeal cancer: A dosimetric comparison.

The current study aims to compare the split x-jaw planning technique of volumetric modulated arc radiotherapy (VMAT) with the traditional open and limited jaw techniques of VAMT in nasopharyngeal carcinoma treatment. The multi-leaf collimators on the varian linear accelerator move on a carriage with a maximum leaf span of 15 cm. Therefore, treatment of larger planning target volumes, such as in nasopharyngeal cancer with traditional open and limited jaw technique, yields compromised dose distribution. Computed tomography data sets of 10 nasopharynx cancer patients were enrolled for the study. For each case, three separate treatment plans were generated viz. open, limited, and split x-jaw planning techniques with similar planning objectives. Only PTVs requiring a field size larger than 18 cm in the x-jaw position were considered. Comparable results were obtained regarding organs at risk (OAR) sparing in all the techniques. The target dose coverage with split x-jaw VMAT was superior to both open and limited jaw planning techniques, with a statistically significant difference in the intermediate dose planning target volumes (PTVs) (PTV59.4), P < 0.05. However, the split technique's dose to the spinal cord and larynx was significantly lower (P < 0.05). The split x-jaw planning technique of VMAT can be adapted for larger PTVs requiring an x-jaw of more than 15 cm. The only concern with this technique is the increased MU.

Compost from willow biomass (Salix viminalis L.) as a horticultural substrate alternative to peat in the production of vegetable transplants

Willow (Salix viminalis L.) is a species well adapted to the environment conditions of central Europe. It is mainly cultivated for energy purposes as solid fuel. In this study, an evaluation of its suitability for other purposes was made using a 4-year old short rotation coppice (SRC) willow regrowth to produce chipped biomass which was composted. Four composting methods were used: without additives (WC), with the addition of nitrogen to narrow the C:N ratio (WN), with the addition of mycelium (WPG) and with the addition of mycelium and nitrogen (WPGN). A mixture of WC and WPGN composts was also prepared at 75:25% and 50:50% by volume. Composts, different proportion (25, 50 and 75%) of peat (SM) were evaluated for suitability as a substrate for tomato and cucumber transplant production. Tomato transplants produced in the medium were prepared from mixtures of willow composts (WPGN + WC(1) and WPGN + WC(2) and these mixtures with peat (WPGN + WC(1):SM and WPGN + WC(2):SM) were characterised as having the best parameters: plant height, lateral leaf span and number of leaves. Similarly, for cucumber transplants, better growth conditions than in peat substrate were obtained in the variant WPGN + WC(1) and WPGN + WC(1):SM. The addition of nitrogen to the composted biomass positively influenced the composting process. N concentration in the substrate was too high and toxic for the growth of tomato and cucumber transplants. At the end of the tomato and cucumber experiment, the nitrate content was 1510 and 2260 mg dm−3, respectively, in the WN substrate. Similarly, the high N–NO3− content in the composted willow substrate with the addition of nitrogen and mycelium did not promote the growth of tomato and cucumber. Based on this research at least 25% of the mass of the peat can be replaced by different willow composts without having an adverse impact on seedling growth and with some of the willow compost mixtures this could be as high as 50%.

Numerical simulation for deformation characteristic of tea shoot under negative pressure guidance by the immersed boundary–lattice Boltzmann method

At present, due to the shortage of tea picking labour force, realizing the mechanized picking of famous tea is urgent. Using negative pressure guidance is a feasible method, which can compensate the localization error of machine vision. In this paper, tea shoot with one bud and two leaves is taken as the study object, and a ‘Y-type’ tea physical model is established according to its physical properties. Moreover, the deformation characteristic of tea shoot under negative pressure guidance is studied by using the immersed boundary–lattice Boltzmann method. The purpose is to analyse the effects of pressure P inside the pipe, vertical deviation H and horizontal deviation W on the deformation characteristics of tea shoot quantitatively. The effectiveness of the numerical calculation method is verified by the negative pressure guiding test. The results show that the success rate of negative pressure guidance is 100% when the leaf span d ≤ 30 mm and the horizontal deviation W ≤ 10 mm. The useful data and insights into the picking technology of famous tea based on negative pressure guidance are provided in this paper according to the findings mentioned above.

INFLUENCE OF THE LEVEL PRUNING ON AGRONOMIC PARAMETERS OF SAVANNAH TEA (LIPPIA MULTIFLORA L., VERBENACEAE) IN YAMOUSSOUKRO, CENTRAL COTE DIVOIRE

On Yamoussoukro autonomous district, a study on the ability of Lippia multiflora L. (Verbenaceae) to shoot and grow was carried out at six soil height levels: 0 cm, 5 cm, 10 cm, 15 cm, 20 cm, 25 cm and 30 cm. The objectif was to determine the favourable levels of pruning for better leaf production. From 28 samples grouped in 7 batches, the pruning was carried out. After 3 months of vegetation, the agronomic parameters of vigour were determined. The results showed that various growth parameters such as number of buds, number of leaves per bud, bud height, leaf length and width as well as budding time and leaf span were measured. Receiving levels at 10 cm, 15 cm and 20 cm from the ground resulted in good leaf production and bud growth.

Unsupervised analysis of NIRS spectra to assess complex plant traits: leaf senescence as a use case

BackgroundAs a rapid and non-destructive method, Near Infrared Spectroscopy is classically proposed to assess plant traits in many scientific fields, to observe enlarged genotype panels and to document the temporal kinetic of some biological processes. Most often, supervised models are used. The signal is calibrated thanks to reference measurements, and dedicated models are generated to predict biological traits. An alternative unsupervised approach considers the whole spectra information in order to point out various matrix changes. Although more generic, and faster to implement, as it does not require a reference data set, this latter approach is rarely used to document biological processes, and does requires more information of the process.MethodsIn our work, an unsupervised model was used to document the flag leaf senescence of durum wheat (Triticum turgidum durum). Leaf spectra changes were observed using Moving Window Principal Component Analysis (MWPCA). The dates related to earlier and later spectra changes were compared to two key points on the senescence time course: senescence onset (T0) and the end of the leaf span (T1) derived from a supervised strategy.ResultsFor almost all leaves and whatever the signal pre-treatments and window size considered, the MWPCA found significant spectral changes. The latter was highly correlated with T1 (0.59 ≤ r ≤ 0.86) whereas the correlations between the first significant spectrum changes and T0 were lower (0.09 ≤ r ≤ 0.56). These different relationships are discussed below since they define the potential as well as the limitations of MWPCA to model biological processes.ConclusionOverall, our study demonstrates that the information contained in the spectra can be used when applying an unsupervised method, here the MWPCA, to characterize a complex biological phenomenon such leaf senescence. It also means that using whole spectra may be relevant in agriculture and plant biology.

Impact of split X-jaw technique on target volume coverage and organ at risk sparing in prostate cancer: a comparative dosimetric study

Abstract Introduction: The Varian Trilogy linear accelerator’s multi-leaf collimator moves on a carriage with a maximum leaf span of 15 cm. The traditional open and limited X-jaw technique of volumetric-modulated arc radiotherapy (VMAT) yields a relatively compromised dose distribution within the planning target volume (PTV) region. This study aimed to determine whether the split X-jaw planning technique for VMAT improves plan quality regarding target dose coverage and organs at risk (OAR) sparing for PTVs that require a field size of more than 15 cm in the X-jaw direction in prostate cancer patients. Method: Computed tomography data sets from 15 patients with prostate cancer were enrolled in the study. Only the PTVs requiring a field size larger than 18 cm in the X-jaw position were considered, and a dose of 4500 cGy in 25 fractions was prescribed. For each case, three separate treatment plans were generated: open, limited and split X-jaw planning techniques with similar planning objectives Results: The split X-jaw technique resulted in statistically significant superior coverage of PTV when compared with the open (P &lt; 0·0001) and limited methods (P &lt; 0·001). The split technique delivered a lower dose to the OARs, although statistical significance could not be achieved. D2% (cGy) was lowest for the PTV in the split technique (4684·8 ± 18·16) and highest for the open technique (4710 ± 18·75), P &lt; 0·001. Conclusion: The x-split jaw technique can replace the traditional open X-jaw practice of VMAT for PTVs requiring an X-jaw width of more than 15 cm in the Varian linear accelerator.

Shortening the Vegetative Growth Stage of Phalaenopsis Queen Beer ‘Mantefon’ by Controlling Light with Calcium Ammonium Nitrate Levels under Enriched CO2

The vegetative growth, photosynthetic, and stomatal characteristics were investigated in Phalaenopsis Queen Beer ‘Mantefon’ to determine light’s influence with calcium ammonium nitrate (CAN) levels under 800 μmol·mol−1 CO2. Two lights (150 ± 20 and 300 ± 20 μmol·m−2·s−1) and CAN levels were employed for 40 weeks: calcium, ammonium, and nitrate levels by 0.90, 0.55, and 2.97 mmol·L−1 (CAN1), 8.63, 1.11, and 6.05 mmol·L−1 (CAN2), 12.80, 1.72, and 9.13 mmol·L−1 (CAN3), and 18.80, 2.27, and 12.20 mmol·L−1 (CAN4), respectively. The number of leaves increased in the plants grown at 300 ± 20 μmol·m−2·s−1 with CAN1 compared to control. Plants grown at 300 ± 20 μmol·m−2·s−1 with CAN4 had the lowest number of leaves among all plants. The time to the mature leaf span decreased in the plants grown at 300 ± 20 μmol·m−2·s−1 with CAN1. The net CO2 uptake was higher in the plants grown at 300 ± 20 μmol·m−2·s−1 than those grown at 150 ± 20 μmol·m−2·s−1 with CAN1–3 conditions. The water-use efficiency is higher in the plants grown with CAN1 than those with CAN2–4 at 300 ± 20 μmol·m−2·s−1. The maximum stomatal aperture was the largest in the plants grown at 300 ± 20 μmol·m−2·s−1 with CAN1–2 among all plants. Consequently, light levels of 300 ± 20 μmol·m−2·s−1 in Phalaenopsis Queen Beer ‘Mantefon’ must be accompanied by nutrient CAN1 to improve photosynthesis and stomatal activity and promote leaf growth under 800 μmol·mol−1 CO2 conditions.

Combining Willow Compost and Peat as Media for Juvenile Tomato Transplant Production

In 2019–2020, a study was conducted to evaluate the suitability of willow composts as a substrate or substrate component in tomato transplant cultivation. In 2019, 4-year-old chopped willow biomass (mostly chips &lt;2 cm long) was formed into four compost prisms: S0—willow compost without additives; SN—willow compost with the addition of nitrogen; SF—willow compost with the addition of wood-decaying mycelium; and SFN—willow compost with the addition of wood-decaying mycelium and nitrogen. Willow compost was rated as a homogeneous substrate (S0, SN, SF, and SFN) and as a substrate component with peat (P), mixed in willow:peat ratios such as 25:75, 50:50, and 75:25, in the variants S0:P, SN:P, SF:P, and SFN:P. For reference, deacidified peat was used as a homogeneous substrate. The study showed that willow compost could be used as a renewable plant material replacing peat. The best parameters (plant height, leaf span, number of leaves, and especially the highest weight) were found in tomato transplants grown in the SF:P and SFN:P substrates and at a 25:75 ratio. It was found that the addition of nitrogen to the compost, in order to obtain a wide C:N ratio, negatively affected the initial growth of tomato plants.

Strategy to implement RapidArc® using HD120™MLC for irradiation of whole pelvis and lower para-aortic lymph nodes in cervical carcinoma

Purpose: To compare the utility of RapidArc® technique with mono or dual isocentre using high-definition 120 multileaf collimator (HD120™MLC) for irradiation of whole pelvis and lower para-aortic lymph node (PALN) in cervical carcinoma.Methods: Ten patients having more than 22-cm treatment target length were delivered 45 Gy in 25 fractions by RapidArc® technique using mono or dual isocenter. Dose distribution characteristics were monitored using various indices. Doses to critical organs were also compared for the sparing effects.Results: Conformity and dose-gradient indices for mono or dual isocenter plans were comparable. However, mono-isocentric plan decreased the heterogeneity index (0.07±0.01) as compared to dual-isocentric plan (0.08±0.01; p&lt;0.05). Mean and maximal doses to various critical organs remained comparable. The mean dose to bowel bag was significantly reduced (p&lt;0.05) in mono-isocentric plan (18.78±5.18 Gy) as compared to dual-isocentric plan (19.20±5.27 Gy). Mono-isocentric plan required 1.3 times higher exposure time than the dual-isocentric plans but reduced the overall treatment time by eliminating intra-fraction patient shift that is inevitable in dual isocenter plan.Discussion: Feasibility of mono-isocentric RapidArc® plan using HD120™MLC for irradiation of whole pelvis and PALN relied on ‘Maximum Leaf Span’, which restricted the ‘leading-leaf’ to surpass the ‘trailing-leaf’ beyond 15-cm. This difficulty was overcome by truncating the field size and fixing the jaws at dedicated positions in mono-isocentric plan.Conclusion: The strategy used in mono-isocentric plan enhanced the utility of RapidArc® using HD120™MLC and also minimized the intra-fraction set-up variations and overall treatment time.

CO2 enrichment increased leaf initiation and photosynthesis in Doritaenopsis Queen Beer ‘Mantefon’ orchids

The plants have potential on carbon sink because plants absorb carbon dioxide (CO2) in ambient and use that for photosynthesis. CO2 enrichment, which is a commonly used technique in vegetable culture, may gain importance in ornamental production, potentially shortening the growth period. However, compared with forests and crop plants, the studies of CO2 enrichment on orchids are relatively limited. This study was undertaken to investigate the effects of elevated CO2 concentrations on leaf initiation and photosynthesis in the orchid Doritaenopsis Queen Beer ‘Mantefon’. Leaf growth and photosynthetic characteristics were measured in the plants grown under 450 (ambient control), 800, and 1600 µmol mol−1 CO2 during the latter 6 h of the dark period for 36 weeks. The number of leaves increased with the elevated CO2 concentration, and the time to leaf initiation decreased with elevated CO2 concentration. However, leaf span and biomass was lower in the plants grown under the higher CO2 concentrations compared to the plants grown under ambient CO2. Maximum net CO2 uptake, transpiration rate, and stomatal conductance were higher in the plants grown under 1600 µmol mol−1 CO2 than in the plants grown under 450 µmol mol−1 CO2. The 800 and 1600 µmol mol−1 CO2 concentrations accelerated leaf initiation and net CO2 uptake. We found that concentrations of CO2 in the 800 and 1600 µmol mol−1 CO2 range were controlled for growth of Doritaenopsis orchids.

Growth and CO2 exchange in young Phalaenopsis orchids grown under different levels of humidity during the vegetative period

Phalaenopsis plants are distributed throughout tropical regions with high humidity, which is generally necessary for their cultivation. This study was conducted to determine the effects of different relative humidity (RH) conditions on the growth and photosynthetic characteristics of young Phalaenopsis plants. Three-month-old clones of Phalaenopsis ‘Blanc Rouge’ and Doritaenopsis ‘Mantefon’ plants were grown under 30 ± 10, 50 ± 10, 70 ± 10, or 90 ± 10% RH conditions. The RH treatments were maintained for approximately 6 months in environment-controlled growth chambers. The temperature and photoperiod were maintained at 28 °C and 12/12 h, respectively. At the start of the RH treatments, the mean leaf span was 14.2 and 16.7 cm in ‘Blanc Rouge’ and ‘Mantefon’ plants, respectively. In both cultivars, plants grown under 70% RH showed the longest leaf span, which was 25.3 and 20.6 cm in ‘Blanc Rouge’ and ‘Mantefon’, respectively. High-humidity conditions (i.e. 70 and 90% RH) generally promoted the length of leaf span, but the growth rate of leaf span was slightly lower at 90% RH than at 70% RH. CO2 exchange, stomatal conductance, and transpiration rate of the uppermost mature leaf were observed in ‘Blanc Rouge’ plants grown at 30, 50, and 70% RH. The highest rate of CO2 uptake was observed in the plants grown at 70% RH, followed by 50 and 30% RH. The stomatal conductance increased and transpiration decreased with increasing RH. The maximum quantum yield of photosystem II (Fv/Fm) of plants grown under 70 and 90% RH slightly decreased after 9 weeks of treatments, but there were no differences among the treatment groups at the conclusion of the study. These results indicated that high RH (e.g. 70%) slightly increases CO2 uptake and leaf span of young Phalaenopsis plants.

Vegetative Growth Characteristics of Phalaenopsis and Doritaenopsis Plants under Different Artificial Lighting Sources

This study was conducted to determine the effects of artificial lighting sources on vegetative growth of Phalaenopsis and Doritaenopsis (an intergeneric hybrid of Doritis and Phalaenopsis) orchids. One - month - old plants were cultivated under fluorescent lamps, cool - white light - emitting diodes (LEDs), or warm - white LEDs at 80 and 160 μ㏖·m -2 ·s -1 . The blue (400 - 500 ㎚) : green (500 - 600 ㎚) : red (600 - 700 ㎚) : far - red (700 - 800 ㎚) ratios of the fluorescent lamps, cool-white LEDs, and warm-white LEDs were 1 : 1.3 : 0.8 : 0.1, 1 : 1.3 : 0.6 : 0.1, and 1 : 2.7 : 2.3 : 0.4, respectively. Each light treatment was maintained for 16 weeks in a closed plant-production system maintained at 28℃ with a 12 h photoperiod. The longest leaf span, as well as the leaf length and width of the uppermost mature leaf, were observed in plants treated with warm-white LEDs. Plants grown under fluorescent lamps had longer and wider leaves with a greater leaf span than plants grown under cool-white LEDs, while the maximum quantum efficiency of photosystem II was higher under cool-white LEDs. The vegetative responses affected by different lighting sources were similar at both 80 and 160 μ㏖·m -2 ·s -1 . Leaf span and root biomass were increased by the higher light intensity in both cultivars, while the relative chlorophyll content was decreased. These results indicate that relatively high intensity light can promote vegetative growth of young Phalaenopsis plants, and that warm - white LEDs, which contain a high red-light ratio, are a better lighting source for the growth of these plants than the cool-white LEDs or fluorescent lamps. These results could therefore be useful in the selection of artificial lighting to maximize vegetative growth of Phalaenopsis plants in a closed plant - production system.

Effects of Light Quality on Vegetative Growth and Flower Initiation in Phalaenopsis

The effects of LEDs (Light-Emitting Diodes) emitting different colours namely red, blue, red andblue, and white lights on vegetative growth and fl ower initiation of Phalaenopsis have been evaluated.Phalaenopsis“otohine/taisuco fi re bird” seedlings in vitro were subjected to different light qualities for either2 or 4 weeks, and then each seedling was planted in a plastic pot containing sphagnum and grown in thegrowth chamber under similar light quality for 3 months. For fl ower induction, mature Phalaenopsis plantshaving 4 – 6 leaves were grown for 3 months in the growth chamber under different light qualities. The leafspan, chlorophyll, gibberellin and cytokinin content were determined. In addition, the expressions of FT-likegene in the leaf, axillary bud, fl ower bud and stalk were examined.Vegetative growth was enhanced under blue, red-blue or white LEDs compared to that of the control.Gibberellin and cytokinin content increased in the seedlings subjected to white LEDs. Based on the averageof leaf span increment it was suggested that the growth of Phalaenopsis seedlings can be promoted by givingeither blue, red-blue or white LEDs. From the second experiment, it was found that fl ower induction inPhalaenopsis can be obtained in plants that had just fi nished fl owering without the application of LEDs. Theexpression of FT-like gene in the leaf as well as fl ower bud and stalk suggests that this gene is involved infl ower regulation of Phalaenopsis.

Dosimetric impact of the 160 MLC on head and neck IMRT treatments.

The purpose of this work is to investigate if the change in plan quality with the finer leaf resolution and lower leakage of the 160 MLC would be dosimetrically significant for head and neck intensity‐modulated radiation therapy (IMRT) treatment plans. The 160 MLC consisting of 80 leaves of 0.5 cm on each bank, a leaf span of 20 cm, and leakage of less than 0.37% without additional backup jaws was compared against the 120 Millennium MLC with 60 leaves of 0.5 and 1.0 cm, a leaf span of 14.5 cm, and leakage of 2.0%. CT image sets of 16 patients previously treated for stage III and IV head and neck carcinomas were replanned on Prowess 5.0 and Eclipse 11.0 using the 160 MLC and the 120 MLC. IMRT constraints for both sets of 6 MV plans were identical and based on RTOG 0522. Dose‐volume histograms (DVHs), minimum dose, mean dose, maximum dose, and dose to 1 cc to the organ at risks (OAR) and the planning target volume, as recommended by QUANTEC 2010, were compared. Both collimators were able to achieve the target dose to the PTVs. The dose to the organs at risk (brainstem, spinal cord, parotids, and larynx) were 1%–12% (i.e., 0.5–8 Gy for a 70 Gy prescription) lower with the 160 MLC compared to the 120 MLC, depending on the proximity of the organ to the target. The large field HN plans generated with the 160 MLC were dosimetrically advantageous for critical structures, especially those located further away from the central axis, without compromising the target volume.PACS number: 87.55 D‐

Phalaenopsis efficiently acclimate to highlight environment through orchid mycorrhization

Phalaenopsis (Phalaenopsis amabilis ‘KC1410’) grow slowly and experience photoinhibition during the daytime. Thus, this study used orchid mycorrhizal (OM) fungus to promote orchid growth hypothetically via increasing the photoacclimation capacity of Phalaenopsis in response to high light (HL). By combining chlorophyll fluorometer and spectral reflectance techniques, the influences of OM colonization on the growth potentials and the photosynthetic performance of HL-grown Phalaenopsis were investigated. OM symbiosis significantly promoted the growth of HL-grown orchids, such as leaf span, fresh weight, and dry weight. Consistent with these observations, OM symbiosis obtained higher value of normalized difference vegetation index (NDVI) and enhanced CO2 uptake rate. This could be attributed to an increase in photosynthetic performance in OM plants. Notably, maximum quantum efficiency of PSII photochemistry (Fv/Fm) was not altered by OM symbiosis, however, the light-adapted fluorescence measurements of PSII operating efficiency (ФPSII) and electron transport rate (ETR) were increased. Nevertheless, OM orchids had higher photochemical quenching (qP) and lower non-photochemical quenching (NPQ). This indicates a relative higher photosynthetic performance and radiation-use efficiency (RUE) in OM plants. The photochemical reflectance index (PRI) as a photoprotection indicator was also enhanced. Based on these results, we proposed that OM symbiosis increases both the photosynthetic performance and the RUE in the HL-acclimated Phalaenopsis, resulting in an advantage to the OM plants to survive the HL stress.

Inhibition of inflorescence initiation in immature Doritaenopsis Queen Beer ‘Mantefon’ by photoperiod and temperature

Inflorescences of Doritaenopsis are commonly induced when the plants are exposed to temperature below 26°C. They need to maintain temperature above 28°C for maintaining the vegetative growth stage and inhibiting inflorescence initiation. We investigated the effects of photoperiod on inflorescence initiation in immature Doritaenopsis at floral inductive temperatures in order to determine an alternative method to prevent inflorescence initiation and to reduce heating expenses. Six-month-old Doritaenopsis Queen Beer ‘Mantefon’ was grown under 9/15 hours (SD), 12/12 hours (MD), 16/8 hours (LD), or SD with night interruption (NI: 22:00–02:00 HR) at 21 or 26°C in module boxes inside a growth chamber. The maximum irradiance was 100 ± 10 and 4 ± 1 μmol·m−2·s−1 during the day and NI, respectively. Inflorescence of the plants was completely inhibited when the plants were grown at 26°C, whereas the plants grown at 21°C could not inhibit inflorescence initiation. However, percent visible inflorescence was reduced greatly in LD when the plants grown at 21°C. NI also reduced visible inflorescence. The LD delayed days to visible inflorescence, followed by MD, NI, and SD when the plants were grown at 21°C. The number of new leaves and leaf span were increased in the plants grown at 26°C more than those grown at 21°C. The plants grown under LD at 21°C had a similar number of new leaves compared to the plants grown at 26°C until 17 weeks of treatment. These results indicated that LD or NI could be an alternative method to high temperature above 26°C for inhibiting inflorescence initiation in immature Doritaenopsis ‘Mantefon’ and could thus save heating costs.

Optimum heating hour to maintain vegetative growth and inhibit premature inflorescence initiation of six-month and one-year-old Phalaenopsis hybrids

This experiment examined the effects of heating hour at 29°C to maintain the vegetative growth and to inhibit premature inflorescence initiation in two stages, immature (6-month-old) and mature (1-year-old), Phalaenopsis hybrids in order to save heating expenses. Plants of Phalaenopsis Norman’s Jade ‘Green Apple’ and Doritaenopsis Queen Beer ‘Mantefon’ at 6-month-old and 1-year-old were grown in separate growth chambers with heating at 29°C for 6, 12, 18, and 24 hours. The photoperiod was 16/8 hours (day/night) consisting of 12 hours PPFD at 120 ± 10 μmol·m−2·s−1 (06:00–18:00 HR) with 4 hours PPFD at 25 ± 10 μmol·m−2·s−1 (18:00–22:00 HR) as a photoperiod-extension. Inflorescence initiation was inhibited in 6-month-old ‘Green Apple’ regardless of the heating hour treatments. However, inflorescence initiation of ‘Mantefon’ at both stages and ‘Green Apple’ at 1-year-old was inhibited only when the plants were exposed at least for 12 hours at 29°C. Overall, the inflorescence initiation of the plants was inhibited or delayed more in 6-month-old plants than 1-year-old plants. Leaf span of the plants was similar among 12, 18, and 24 hours-29°C treatments, except for 6 hours-29°C treatment. In conclusion, it is recommended that high temperature heating at 29°C for at least 12 hours during the day could increase vegetative growth sufficiently and prevent premature inflorescence initiation completely, even though nigh temperature decreased to 20°C in Phalaenopsis hybrids at immature stage. These approaches could be used to save heating cost during the winter season cultivation.

Effects of Paclobutrazol Sprays on Inflorescences of Three Potted Moth Orchid Clones

Inflorescences of some moth orchid (Phalaenopsis and Doritaenopsis) hybrids can become very tall, which can pose shipping challenges for commercial producers and be unwieldy for consumers. We determined the efficacy of paclobutrazol as a foliar spray to inhibit inflorescence elongation of these genera and intergeneric hybrids. A single application of 15, 30, or 45 mg·L−1 palcobutrazol at a volume of 0.2 L·m−2 was applied to Doritaenopsis Miss Saigon, Doritaenopsis Andrew, and Phalaenopsis ‘Smart Thing’ grown at 23 °C to induce flowering. Applications were made after inflorescence emergence but before flower initiation (inflorescences were 1 to 2 cm long) or after flower initiation (inflorescences were 10 to 18 cm long). None of the paclobutrazol applications inhibited total inflorescence elongation of ‘Smart Thing’ or Miss Saigon. However, paclobutrazol inhibited inflorescence elongation from treatment until first flowering of Andrew by 19% to 23% when plants were treated with 15 or 45 mg·L−1 before flower initiation and 30 or 45 mg·L−1 after flower initiation. One or more concentrations of paclobutrazol applied after flower initiation reduced the length of the internode between the first and second flower on all three orchid clones. Paclobutrazol delayed flowering only on Miss Saigon (by 2 days) and only when applied after flower initiation. Paclobutrazol application did not affect the number of inflorescences or flowers, diameter of the first flower, number of new leaves formed, or increase in leaf span. Growers are advised to perform small-scale trials with paclobutrazol solutions starting at 30 to 45 mg·L−1 within 1 week of inflorescence emergence, although higher concentrations may be appropriate for the most vigorous varieties. Furthermore, a late spray application can cause unwanted crowding of the flowers.

High-temperature Inhibition of Flowering of Phalaenopsis and Doritaenopsis Orchids

Phalaenopsis orchids require a day temperature of 26 °C or less to initiate inflorescences, whereas the night temperature has little or no effect on inflorescence initiation. We determined the duration of high temperature required each day to prevent inflorescence initiation of four Phalaenopsis and Doritaenopsis clones. In Years 1 and 2, mature potted plants were grown in separate greenhouse sections with five daily durations at 29 °C: 0, 4, 8, 12, or 24 h. The high temperature was centered in the 16-h photoperiod (0600 hr to 2200 hr) and the remainder of the day was at 20 °C. Exposure to 29 °C for 8 h or longer inhibited inflorescence initiation of Phalaenopsis Miva Smartissimo × Canberra ‘Mosella’ and Phalaenopsis Brother Pink Mask × Brother Success ‘Explosion’, but Phalaenopsis Baldan's Kaleidoscope ‘Golden Treasure’ and Doritaenopsis ‘Newberry Parfait’ required exposure to 29 °C for 12 h or longer to inhibit inflorescence initiation. Flowering was completely suppressed only when high-temperature exposure time was continual for Doritaenopsis ‘Newberry Parfait’ and Phalaenopsis Baldan's Kaleidoscope ‘Golden Treasure’ and 12 h for Phalaenopsis ‘Mosella’. Plant leaf span generally increased as duration of exposure to 29 °C increased, but high-temperature exposure had few or no significant effects on flowering characteristics of flowering plants. These studies indicate that as few as 8 h of high temperature can prevent flowering of some Phalaenopsis hybrids, whereas others require greater than 12 h of high-temperature exposure.

SU‐FF‐T‐100: The Dosimetric Impact of the New 160MLC On Head and Neck IMRT Treatments

Purpose: The purpose of this work is to investigate if the change in plan quality with the finer leaf resolution and lower leakage of the 160 MLC would be dosimetrically significant for head and neck IMRT treatment plans. Method and Materials: The 160 MLC™ (Siemens Medical Solutions) consists of 80 leaves of 0.5 cm on each bank, a leaf span of 20 cm and leakage of less than 0.37 % without additional back up jaws. CT image sets of 10 patients of previously treated with stage III and IV head and neck carcinomas (HN) were re‐planned on Prowess 4.6 (Prowess Inc., Ca) using the 160 MLC™ (Siemens Medical Solutions, Erlangen, Germany) and the 120 MLC (Varian Medical Systems, Inc., Ca). The underlying beam data for both the treatment units on the planning system were matched to within 1%. IMRT constraints for both 6 MV plans were identical. We compared dose volume histograms (DVHs), minimum, mean and maximum dose to the organ at risks (OAR), the planning target volume (PTV and conformity index. Results: The dose to the organs at risk were 2 – 5% (i.e 1.5 – 3 Gys for a 70 Gy prescription) lower with the 160 MLC compared to the 120 MLC. The PTV conformity index between the 160 MLC and the 120 MLC were similar. Besides dosimetry, the plans generated on the 120 MLC had multiple split fields resulting in almost double the number of treatment fields. Conclusion: The large field HN plans generated with the 160 MLC are dosimetrically advantageous for critical structures especially when they are located further away from the central axis, without compromising target volume coverage. The 20 cm leaf span also reduces the number of split fields which is likely to reduce delivery time.