Average Internode Length Research Articles

A CONCEPTUAL DYNAMIC MODEL FOR EXTERNAL QUALITY IN KALANCHOE

Modelling quality in pot plants is still a weak feature in crop modelling research. This work aims at building a conceptual dynamic model for external quality (plant height and number of flower heads) in Kalanchoe blossfeldiana. Four experiments were conducted to quantify the effects of temperature and spacing schedules at two different planting dates. Five constant temperatures (18, 20, 22, 24 and 26°C) and nine spacing schedules, resulting from combinations of spacing at a given leaf area index (LAI: 1.6, 2, 3, 4 and 4.4) into a final plant density (31.1, 34.6, 43.4, 52.0 and 55.6 plants m-2) were studied. Stem length was modelled as the number of internodes (same as number of leaf pairs) times the average internode length. Plant height results from the stem length plus the uppermost pedicel length. The spacing schedules did not affect plant height, but total aerial dry mass (TDM, g plant-1), leaf area and number of flower heads were increased at earlier and wider spacing. In contrast, temperature had a significant effect on the average internode length (internode elongation rate linearly increased with temperature) and on the generative length (optimum response to temperature). However, internode appearance rate was not affected by temperature. Number of flower heads showed a positive linear relationship with TDM. Therefore, by simulating TDM the number of flower heads can be predicted. TDM was simulated based on the intercepted photosynthetic active radiation and light use efficiency. The reaction time showed a quadratic response to temperature, with a maximum rate of progress to flower at 23°C (10 days delay at 18°C). These modules need to be validated to form the basis of a year-round decision support system for Kalanchoe.

Chronic nerve compression induces local demyelination and remyelination in a rat model of carpal tunnel syndrome

In a previous study, we demonstrated that chronic compression of rat sciatic nerve, a model of compressive neuropathies, triggered dramatic Schwann cell proliferation and concurrent apoptosis. Importantly, this Schwann cell response occurred before there are signs of overt axonal pathology, raising the question of whether there are alterations in axonal myelination in the areas of the nerve in which Schwann cell apoptosis and proliferation occur. Here, we use nerve teasing techniques and unbiased stereology to assess myelination in nerves after 1 and 8 months of compression. Evaluations of myelin thickness and axonal diameter (AD) using design-based, unbiased stereology revealed alterations in myelin structure that indicate remyelination, specifically a dramatic decrease in the average internodal length (IL) and an increase in the proportion of axons with thin myelin sheaths. The mean IL was reduced after 1 month of chronic nerve injury with no further decrease in IL at 8 months. There was limited change in average axonal diameter at both 1 and 8 months. Measures of myelin thickness revealed not only a greater than 6-fold increase in the number of axons with very thin (<5 μm thickness) myelin sheaths, but also a proportional decrease in the number of axons with the thick myelin sheaths characteristic of normal nerve. These results confirm that an early consequence of chronic nerve compression (CNC) is local demyelination and remyelination, which may be the primary cause of alterations in nerve function during the early period post-compression.

Cotton responses to ultraviolet-B radiation: experimentation and algorithm development

The potential impact of an increase in solar ultraviolet-B (UV-B) radiation due to human activity on higher plants has been the subject of many studies. Little work has been carried out so far on cotton responses to enhanced UV-B radiation. The objective of this study was to determine whether or not the current and projected increases in UV-B levels affect cotton growth and development, and to quantify and develop UV-B radiation functional algorithms that can be used in simulation models. Two experiments were conducted during the summer of 2001 using sunlit plant growth chambers in a wide range of UV-B radiations under optimal growing conditions. Leaves exposed to UV-B radiation developed chlorotic and necrotic patches depending on the intensity and length of exposure. Along with changes in visible morphology, cotton canopy photosynthesis declined with increased UV-B radiation. The decline in canopy photosynthesis was partly due to loss of photosynthetic pigments and UV-B-induced decay of leaf-level photosynthetic efficiency (maximum photosynthesis) and capacity (quantum yield) as the leaves aged. The total leaf area was less due to smaller leaves and fewer leaves per plant. Less plant height was closely related to a shorter average internode length rather than a fewer mainstem nodes. The UV-B did not affect cotton major developmental events such as time taken to square, time to flower, and leaf addition rates on the mainstem. Lower biomass was closely related to both smaller leaf area and lower photosynthesis. The critical limit, defined as 90% of optimum or the control, for stem elongation was lower (8.7 kJ m −2 per day UV-B) than the critical limit for leaf expansion (11.2 kJ m −2 per day UV-B), indicating that stem elongation was more sensitive to UV-B than leaf expansion. The critical limits for canopy photosynthesis and total dry weight were 7 and 7.3 kJ m −2 per day, respectively. The identified UV-B-specific indices for stem and leaf growth and photosynthesis parameters may be incorporated into cotton simulation models such as GOSSYM to predict yields under present and future climatic conditions.

Application of architectural analysis and AMAPmod methodology to study dwarfing phenomenon: the branch structure of 'Royal Gala' apple grafted on dwarfing and non-dwarfing rootstock/interstock combinations.

Architectural analysis was applied to study branch development of 'Royal Gala' apple trees grafted with dwarfing and non-dwarfing rootstock/interstock combinations, which had been chosen to produce trees with a wide range of vigour. Using AMAPmod methodology, the structure of 3-year-old branches was described at four levels of representation: branch; annual shoot; growth unit; and node. Three types of growth units were distinguished: extension growth unit (vegetative unit with internode extension); vegetative spur with minimal internode extension; and fruiting spur or bourse. The aim of the analysis was to describe exactly how the rootstock/interstock combinations affected the structure building process. The number of extension growth units, vegetative spurs and fruiting spurs per annual shoot changed over the years, but this was not affected by rootstock/interstock combination. Compared with MM.106 rootstock, M.9 rootstock reduced the number of nodes per extension growth unit. In most cases, rootstock/interstock combination had no effect on the linear relationship between extension growth unit length and node number (R(2) = 0.88). Average internode length depended on unit node number, with internodes being shorter for units with fewer nodes. Thus the difference in apple branch size induced by the rootstock/interstock combinations was mainly due to a reduction in the length and number of neoformed nodes produced on extension growth units. As percentage budbreak of axillary buds on extension growth units was not affected by rootstock/interstock combination, differences in numbers of axillary annual shoots per branch were entirely due to differences in the total numbers of nodes extended during the previous year.

Triple test cross analysis for some morphological traits in mungbean (Vigna radiata (L.) Wilczek)

Thirty progenies of mungbean were produced by crossing 10 true-breeding genotypes with three testers (NM 92, 6601, and their F1) in a Triple Test cross (TTC) fashion and evaluated with parents in the kharif (July-October) and spring/summer (March-June) seasons. The data on parents and F1s were analysed for pod clusters on main stem, pod clusters on branches, node of the first peduncle, nodes on main stem and average internode length to detect epistasis and estimate additive and dominance components of genetic variation. Epistasis was observed for node of the first peduncle and nodes on main stem in the kharif season. Partitioning of total epistasis revealed that both additive × additive (i type), and additive × dominance, and dominance × dominance (j and l types) interactions were significant with prevalent influence of i type interactions on these traits. Both additive and dominance components of genetic variation were significant for all those traits not significantly influenced by epistasis in either or both seasons. The additive component was predominant for pod clusters on main stem, pod clusters on branches and average internode length in the kharif season, and for the node of the first peduncle and nodes on main stem in spring/summer season whereas dominance component was important for pod clusters on main stem, pod clusters on branches, and average internode length in spring/summer season. These results suggested that particular generation of segregating population and specific breeding method for selection might be adopted in each season for the improvement of these traits in mungbean.

Effects of Light Quality, Intensity and Duration from Different Artificial Light Sources on the Growth of Petunia (Petunia*hybrida Vilm.).

The effect of light quality on the growth of petunia (Petunia×hybrida Vilm.) 'Baccarat Blue Picotee' was studied. Petunias were grown in growth chambers under a metal halide (MH), high pressure sodium (HPS) and blue (B) lamps, at different light intensities and duration, additionally, these were sprayed with GA3 and Uniconazol, a growth retardant. 1. Plant shapes were more compact under HPS than under MH or B. The longest lateral shoot under HPS was about 30% shorter than that of plants grown under MH or B. The average internode length was also shorter under HPS than the others ; this result is attributed to the high-red : far-red light ratio (R/FR) of HPS, which was mediated by plant phytochromes. 2. Light intensities also influenced plant height, which increased with decreasing light intensity under MH and HPS. Furthermore, plant height and stem length under HPS were shorter than those under MH in all light intensities. 3. The rate of shoot elongation was reduced when the plants were transferred from MH to HPS. The final light quality determined the plant height. But, it had no residual effect. 4. The growth inhibition by HPS was reversible by the application of GA3. Whereas, Uniconazol had no effect on stems exposed to HPS. These results suggest that the high R/FR ratio of HPS inhibits GA synthesis and, therefore, plant height was shorter than plant exposed to which has a lower R/FR ratio.

Morphological and mechanical properties of Miscanthus in relation to harvesting, lodging, and growth conditions

Field experiments with Miscanthus ‘ giganteus’ and Miscanthus ‘ sinensis’ including studies concerning effects of harvest time, lodging, pruning, and fertilisation on morphological and mechanical properties were conducted. Stem length increased from the first to the second harvest and then decreased due to natural internode abscission starting at the upper internodes. An average of three internodes was lost from the stems. The lengths of internodes 2 and 4 were independent of harvest time. However, the lengths of the upper internodes were at a minimum at harvest times 2–4. The internode length increased from the second to the fourth internode and then followed by a decrease. Outer diameter, inner diameter, culm wall thickness, moment of inertia, modulus of elasticity, and flexural rigidity decreased from the lower to the upper nodes and internodes. Average internode length, culm wall thickness, internal diameter, outer diameter, moment of inertia (I) of internodes, and modulus of elasticity of internodes were not influenced by harvest time. Moment of inertia was high and modulus of elasticity was low for internodes compared to the nodes. However, the flexural rigidity was highest for internodes. The measured values for modulus of elasticity ranged from 2–8 GPa. Pruning of the crop and use of a minimum of nitrogen fertilizer reduced the risk of lodging.

Componentes morfológicos e produção de matéria seca de milho em função da aplicação de calcário e zinco&lt;A NAME="top"&gt;&lt;/A&gt;

O milho é uma das plantas que mais responde positivamente à aplicação de zinco no solo, com ganhos na produção de matéria seca e grãos. Entretanto, a disponibilidade e a absorção do elemento pelas plantas são influenciadas negativamente pela elevação do pH, da V% e do teor de P nos solos. Para estudar o efeito da calagem e do zinco aplicado na adubação, e o seus efeitos residuais sobre a produção de matéria seca e o desenvolvimento das plantas de milho, foram realizados três cultivos subsequentes, em condição de casa de vegetação, utilizando-se vasos que receberam 20 kg de um Latossolo Vermelho distrófico. O delineamento experimental foi inteiramente casualizado em esquema fatorial 3x3, com três saturações por bases (15, 50 e 70%) e três teores de zinco no solo (0,70, 5 e 10 mg dm-3), com quatro repetições. Em cada cultivo deixaram-se duas plantas de milho (híbrido tríplo XL 370) por vaso até os 57 dias após a emergência, momento em que foi realizada a colheita para a determinação da produção de matéria seca. A análise de desenvolvimento da planta foi realizada a cada sete dias, avaliando-se: altura média, número de folhas e comprimento médio de entrenós/planta, num total de oito coletas. A aplicação de zinco não alterou as variáveis morfológicas da planta de milho. A calagem incrementou a altura das plantas. O aumento da dose de calcário resultou em maior produção de matéria seca e teores de Ca e Mg nas folhas e colmos de milho. A aplicação de zinco incrementou os teores do elemento na matéria seca. Houve efeito residual da calagem e da adubação com zinco na produção de matéria seca em três cultivos de milho.

Crescimento do milho em função da saturação por bases e da adubação potássica

Os teores de Ca, Mg e K no solo interferem no crescimento e na produção das culturas. No entanto, a relação entre esses nutrientes que proporciona o desenvolvimento adequado das plantas varia entre as espécies vegetais. O presente teve por objetivo estudar o desenvolvimento do milho em função da saturação do solo por bases e adubação potássica. O delineamento experimental foi inteiramente casualizado, com quatro repetições, em esquema fatorial 3x2x4, constituindo-se de três solos (Neossolo Quartzarênico, Latossolo Vermelho e Latossolo Bruno), dois valores de saturação por bases (40 e 70 %) e quatro doses de potássio no solo (0, 60, 120 e 240 mg kg-1). O experimento foi conduzido em casa-de-vegetação, utilizando-se o milho cv. Zêneca 8392 com uma planta por vaso de 30 L. Aos 29, 57 e 127 dias após a emergência das plântulas, efetuaram-se medidas do número de folhas por planta, altura média das plantas, diâmetro basal do colmo e comprimento médio de entrenós. Após a colheita final determinou-se a produção de grãos por planta. O desenvolvimento e a produção de grãos do milho aumentou até a adição de 60 mg kg-1 de K ao solo. O crescimento do milho foi mais rápido no solo mais arenoso, até o florescimento masculino. Solos com maior capacidade de troca catiônica proporcionaram maior comprimento de entrenós. O comprimento médio de entrenós foi inversamente relacionado ao número médio de entrenós por planta, em função do tipo de solo.

Inheritance of Some Important Agronomic Traits in Mungbean (Vigna radiata (L.) Wilczek).

The inheritance of some important agronomic traits (the node of the first peduncle, nodes on main stem, average internode length, pod clusters on main stem and pod clusters on branches) has been studied through a half diallel cross of six diverse mungbean genotypes. Additive and dominant gene actions were responsible for the inheritance of node of the first peduncle, pod clusters on main stem and pod clusters on branches, whereas only additive gene effects were responsible for nodes on main stem and average internode length. However, the additive gene effects were predominant for all these traits. For the lower node of the pod peduncle, the cultivar, NM 92 and combination, NM 92×VC 3902A were the best general and specific combiners, respectively. The combination NM 92×6601 may be used directly to select lodging-resistant mungbean genotypes. High narrow-sense heritability estimates for node of the first peduncle and average internodal length indicated the possibility of developing mungbean genotypes with pod peduncles starting from lower nodes and resistant to lodging.

Modification of Plant Architecture in Chrysanthemum by Ectopic Expression of the Tobacco Phytochrome B1 Gene

Height control is a major consideration during commercial production of chrysanthemum [Dendranthema×grandiflora Kitam. (syn. Chrysanthemum×morifolium Ramat.)]. We have addressed this problem by a biotechnological approach. Plants of `Iridon' chrysanthemum were genetically engineered to ectopically express a tobacco (Nicotiana tabacum L.) phytochrome B1 gene under the control of the CaMV 35S promoter. The transgenic plants were shorter in stature and had larger branch angles than wild type (WT) plants. Reduction in growth caused by the ectopic expression of the tobacco phytochrome B1 gene was similar to that caused using a commercial growth retardant at the recommended rate. Another morphological effect observed in the leaves of the transgenic plants was more intense green color that was related to higher levels of chlorophyll. The transgenic plants appeared very similar to WT plants grown under a filter that selectively attenuated far red wavelengths. Furthermore, when plants were treated either with gibberellin A3 (which promoted growth) or 2-chlorocholine chloride, an inhibitor of gibberellin biosynthesis (which inhibited growth) the difference in the average internode length between the transgenic plants and WT plants was the same in absolute terms. This suggests that reduction of growth by the expressed PHY-B1 transgene did not directly involve gibberellin biosynthesis. The commercial application of this biotechnology could provide an economic alternative to the use of chemical growth regulators, thereby reducing production costs.

196 Growth of Grapevines With and Without Grow Tubes

Grapevines (cv. Steuben) were field-grown for 1 year to determine the effects of pruning and grow tube use on vine growth. Plots were grown on Crosby-Miami silt loam soils, trickle irrigated as needed to ensure adequate moisture, and provided a 3-ft band of weed control on each side of the row. Vines were trained onto a 5-ft. tall-trellis using the following techniques: 1) pruned to a single shoot and placed in a grow tube supported by a bamboo stake, 2) pruned to a single shoot and trained on a bamboo stake without a grow tube, or 3) left unpruned and trained on four strings radiating out from the vine to the top wire. At the end of the growing season, the vines were destructively sampled for leaf area, total shoot growth, average internode length, shoot diameter, top growth dry weight, and root system dry weight. The results indicate that pruning vines to a single shoot significantly reduced overall vine growth, whether a tube was used or not. Vines trained to single shoots and grown with or without grow tubes did not differ significantly for the various parameters measured. Unpruned vines produced nearly three times more leaf area, more than two times more total shoot length, and more than two times more top dry weight and root dry weight than the other treatments. A sub-set of these vines will be grown for one more season to determine if the negative effects of pruning and/or tubes will effect vine size after a second season.

569 Photoselective Filters Affect Flowering and Stem Extension In Viola ×wittrockiana and Pisum sativum

For many plants, light quality has a pronounced effect on plant morphology; light with a low red (R, 600 to 700 nm) to far-red (FR, 700 to 800 nm) ratio promotes stem elongation and a high R: FR, or blue light (B, 400 to 500 nm), suppresses it. In addition, FR light is required for rapid flowering in some species, particularly for long-day plants. Our objective was to quantify how flexible spectral filters, which selectively reduce FR, B, or R, influence plant height and flowering of the quantitative long-day plants Pisum sativum L. `Utrillo' and Viola ×wittrockiana Gams. `Crystal Bowl Yellow'. Plants were grown at 20 °C with reduced FR, B, or R environments or with a neutral density control (C) filter. Calculated phytochrome photoequilebria were 0.78, 0.73, 0.71, or 0.46 for the altered FR, B, C, or R environments, respectively. All filter treatments transmitted a similar photosynthetic photon flux. Sixteen-hour photoperiods were created with natural daylight supplemented with high-pressure sodium lamps positioned above filters. Viola grown under the FR filter never reached 100% flowering within 8 weeks, and visible bud appearance was delayed by at least 17 days compared to all other filters. The R and B filters enhanced peduncle length by at least 25% compared to the C or FR filters. In Pisum, average internode length was 2.2, 2.9, 3.4, and 3.7 cm under the FR, C, B, and R filters, respectively, all statistically different. Fresh and dry shoot weights were similar under the C and FR filters but were at least 35% greater under the B filter and 35% lower under the R filter.

USING DIF TO SHORTEN INTERNODES AND INCREASE HEAT TOLERANCE IN GREENHOUSE GROWN WATERMELONS (CITRULLUS LANATUS THUNB. 'BINKNA' AND 'KAMRO')

Watermelon plants were grown for 30 days in all combinations of day and night temperatures of 25°C, 30°C, and 35°C; yielding 9 separate treatments with DIFs from -10 to +10. At harvest, plant internode length, dry weight, total chlorophyll, number of flowers and heat tolerance were measured. Dry weight accumulation was very sensitive to average daily temperature with plants grown at 35/30°C (DT/NT) being the most sensitive. However, within the same average daily temperatures, a negative DIF had no effect on total dry matter accumulation. A negative DIF did shorten the average internode length as compared to the plants with no DIF or plants grown under a positive DIF. Flowering of these cultivars appeared to be promoted by increasing day temperature, while high night temperature regimes of 35°C significantly reduced it as compared to 30°C night temperature regimes. Growth at a higher average daily temperature with DIF significantly increased the heat tolerance as measured by chlorophyll fluorescence. There was no significant difference in heat tolerance between negative DIF and positive DIF grown watermelon. However, these results suggest that watermelon morphology can be controlled by DIF treatment during the seedling stage. The shortening of distance between the first 14 internodes where fruits are set, will result in more compact plants which are easier to harvest.

Sheath lengths of large motor axons in the ventral root L5 of neonatal and adult rats

This study examines the developmental sheath elongation in the rat ventral root L5. Electron microscopic analysis of serial transverse sections through roots from newborn rats shows an average internuclear distance (IND) of 66 μm (calculated fresh length 73 μm). Light microscopic analysis of teased adult roots shows that the largest fibers have an average internodal length of some 1250 μm at 5 months. Hence, large fibers exhibit a developmental sheath elongation of 17 times. The ventral root L5 elongates 11 times only. This mismatch necessitates a myelin sheath remodelling.

Growth Response of 20 Seed Geranium Cultivars to Three Day–Night Temperature Regimes

The influence of temperature and genotype on plant height, internode length, and morphological development of 20 cultivars of Pelargonium ×hortorum Bailey were determined by growing plants under one of three day–night temperature regimes (18/18C, 18/24C, and 24/18C). Temperature regime influenced internode length and plant height regardless of plant genotype. Internode length and plant height increased as the day–night temperature differential (DIF) increased from –6 to 6C. Average internode length increased from 5.3 ± 0.2 mm for –6C DIF to 6.3 ± 0.2 mm for +6C DIF. Genotypes differed for average internode length (4.2 to 8.7 mm) and plant height (54 to 95 mm). Node count increased as average daily temperature (ADT) increased. Node counts were 11.2 at 18/18C (ADT = 18), 11.9 at 24/18C (ADT = 20.3), and 12.1 at 18/24C (ADT = 21.8). Genotype × temperature interactions were not significant for the recorded traits. This study demonstrates that DIF is an effective height control strategy, regardless of geranium genotype, and that DIF combined with the selection of genetically short cultivars may eliminate the need for chemical height control in the commercial production of geraniums.

Shoot Growth Rate and Density Affect Bud Necrosis of `Riesling' Grapevines

Examination of `Riesling' grape (Vitis vinifera L.) in Virginia suggested that a high incidence of bud necrosis (BN) in some vineyards was associated with canopy shade and rapid shoot growth. BN appeared to originate as an abortion and dehydration of the primary, and occasionally secondary, buds of the developing dormant bud. BN frequency was lowest among the basal four nodes of a given shoot or cane, and increased in frequency through node 20. Experiments were conducted in 1991 and 1992 to evaluate the specific involvement of shoot growth rate and canopy shade on `Riesling' BN. Shoot growth rate (SGR), measured in a 17-day period around bloom, had a significant, positive relationship with BN in one of two vineyards. BN was positively associated with cane diameter and average internode length. Applying the growth retardant paclobutrazol significantly reduced SGR and BN incidence up to 80% among nodes 6 to 15 in two separate vineyards. Artificial shade (64% or 92% reduction in photosynthetic photon flux), suspended over vine canopies in the 3-week period before véraison, did not affect BN. Shoots of canopies that had been thinned before bloom to 10 shoots/m of canopy expressed slightly lower BN levels than shoots sampled from canopies that had been thinned to 20 shoots per meter. `Riesling' BN appeared more influenced by shoot vigor than shade under Virginia growing conditions. Chemical name β-[(4-chlorophenyl)methyl]-α-(1,1-dimethyl-ethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Effects of Different Durations and Timing of Far-red-deficient Environments on Chrysanthemum Growth

The effect on plant height and internode length of `Iridon' chrysanthemum by far-red-deficient environments for two different durations was evaluated. Far-red deficiency was achieved by placing plants under double-walled polycarbonate panels filled with 6% (w/v) copper sulfate (CuSO4) solution. Controls were polycarbonate panels without CuSO4 solution. The plants were divided at random into four groups. One group was exposed all day to the CuSO4-filtered (ADCu) environment and another to all-day clear (ADCl) environment. Another set of plants were grown under CuSO4 filters and moved under clear filters 1 h before sunset each day (EODCl), while the last set of plants were grown under clear panels and moved under CuSO4 panels 1 h before sunset each day (EODCu). Plants moved at the end of the day were moved back to their original chambers after dark each night. The experiment was replicated. Overall change in plant height and average internode lengths were measured. The results were compared to ADCl (control). A 31% reduction in plant height was observed for EODCl, 42% reduction for ADCu, and 25% reduction for EODCu. Average internode length was reduced 11% for EODCl, 14% for EODCu, and 33% for ADCu.

Light Quality Initiating or Ending the Day Affects Internode Length in Petunia

`Ultra Rose Star' petunia plants were germinated and grown at 21C. The study was initiated 26 days after seeding and the photoperiod was 15 h of light and 9 h of darkness. During the initial or ending 90 min of the light period, the plants were exposed to a light quality of a higher (≈2.0) or lower (≈0.8) red (R, 660 nm) to far red (FR, 730 nm) ratio than daylight (R: FR, ≈1.1). Flowering occurred within 65 days from seeding for plants in all treatments. Plants receiving a low R: FR during the initial 90 min of the day had similar internode lengths as those plants receiving a high R: FR at the end of the day. The average internode length of the main stem at flowering was 0.6 ± 0.08 cm for plants receiving a low R: FR in the morning or a high R: FR at the end of the day. In addition, the internodes of those plants exposed to a low R: FR in the morning were longer than on plants receiving a low R: FR at night or a high R: FR in the morning. The average internode length at flowering was 0.4 ± 0.08 cm for plants with an ending low R: FR or a beginning high R: FR light quality of the day.

Hyphal Morphology Associated with Strain Instability in the Commercial Mushroom, Agaricus bisporus

Light microscopy was used to examine the morphology of surface hyphae of strains of Agaricus bisporus that form “fluffy” or “stromatal” sectors on agar medium or in grain culture. Although differences were found between normal (U1 strain) and some sectoring isolates in the mean distance from the hyphal apex to the first branch, and in average internode length, these differences were not consistent under different growth conditions. Fluffy and stromatal isolates did show a high frequency of hyphae with irregular branching patterns. A correlation between high prevalence of hyphae with certain types of branching patterns and the ability to form sectors in grain culture was also observed in 35 single-basidiospore isolates derived from mushrooms produced by normal and sectoring cultures. It is suggested that the ability of any subculture to form a sector may depend on the prevalence of aberrent hyphae in the initial inoculum.