Photoperiod Responses of Corchorus olitorius L. in Controlled Environments

Controlled environments were used to establish the base-linegrowth and to evaluate the photoperiodic response of two Tossajute (Corchorus olitorius) cultivars. Fresh and dry weightsof shoots and roots, leaf areas and stem lengths were much greaterat long day (LD) 12·5, 11·5 than LD 11·5,12·5 photoperiods for both cultivars. Root lengths weregreater at LD 12·5, 11·5 initially but were longestat LD 11·5, 12·5 at 35 days from emergence. Meanrelative growth rates (MRGR) were similar irrespective of photoperiodor cultivar but declined with plant age. The superior growthof cultivar ‘Yaya’ at LD 12·5, 11·5was due to more growth in the first 7 days, while, for cultivar‘Angbadu’ it was a combination of growth for 7 days,and higher MRGR up to 21 days. Stomatal density was greaterat LD 12·5, 11·5 than LD 11·5, 12·5. Corchorus olitorius L., Tossa jute, photoperiodism, relative growth rate     

Temperature and Photoperiod Influence Trichome Density and Sesquiterpene Content of Lycopersicon hirsutum f. hirsutum

Resistance to Colorado potato beetle in a clone of Lycopersicon hirsutum f. hirsutum L. is attributed to the presence of the sesquiterpene zingiberene in the type VI leaf trichomes; however, both day/night temperature regimen and photoperiod affect zingiberene content and trichome density. In short days (SD), zingiberene content per trichome is more than 3-fold greater than in long days. In SD, trichome density per unit leaf surface is 2-fold greater at 25/20°C (day/night) than at either 30/25°C or 20/15°C, thus indirectly influencing zingiberene content per cm². In long days, temperature regimen had little effect on either trichome density or zingiberene content, although trichome density was greater than or equal to that in SD.     

Dormancy and Flowering in Anemone coronaria L. as Affected by Photoperiod and Temperature

The effects of day-length and temperature on flowering and dormancyinduction were studied in Anemone coronaria L., with plantsraised either from corms or achenes. An Israeli hybrid sourcewas used (de Caen cv. Hollandia x Israeli wild type). Dormancy onset is characterized by the cessation of foliageleaf production, the appearance of leaf scales protecting theperennating bud, and leaf senescence. Dormancy was induced byhigh temperature and long days but increasing temperatures (from17/12 °C to 32/12 °C) induced earlier dormancy thanprolonging the photoperiod (range 8–16 h). A significant(P = 0.01) interaction was found between these factors, withsmaller photoperiodic effects the higher the temperature. At22/17 °C the critical day-length for dormancy inductionwas between 11 and 12 h. The transition from the vegetative to the reproductive stageappears to be an autonomous process that occurs with developmentin plants raised from either corms or achenes and does not requireenvironmental induction. Photo- and thermoperiodic effects onflowering were indirect, being mediated through their influenceon dormancy induction. Anemone coronaria L., dormancy, flowering, photoperiod, thermoperiod     

Single gene control of postzygotic self-incompatibility in poke milkweed, Asclepias exaltata L

Most individuals of Asclepias exaltata are self-sterile, but all plants lack prezygotic barriers to self-fertilization. To determine whether postzygotic rejection of self-fertilized ovules is due to late-acting self-incompatibility or to extreme, early acting inbreeding depression, we performed three diallel crosses among self-sterile plants related as full-sibs. The full-sibs segregated into four compatibility classes, suggesting that late acting self-incompatibility is controlled by a single gene (S-locus). Crosses between plants sharing one or both alleles at the S-locus are incompatible. An additional diallel cross was done among full-sib progeny from a cross of a self-sterile and a self-fertile plant. These progeny grouped into two compatibility classes, and plants within classes displayed varying levels of self-fertility. This suggests that the occasional self-fertility documented in natural pollinations is caused by pseudo-self-fertility alleles that alter the functioning of the S-locus.     

Effects of pre-storage conditions on storage of in vitro cultures of Nephrolepis exaltata (L.) Schott and Cordyline fruticosa (L.) A. Chev.

In vitro cultures of Nephrolepis exaltata and Cordyline fruticosa were stored at 5°, 9° or 13°C, at a low irradiance (3–5 mol m^–2 s^–1) or in darkness. Prior to storage the cultures were subjected to 18°, 21°, 24° or 27°C and 15, 30 or 45 mol m^–2 s^–1 in a factorial combination.The optimal storage conditions for Nephrolepis were 9°C in complete darkness. These cultures were still transferable to a peat/perlite mixture at the end of the experimental period of 36 months.The optimal storage conditions for Cordyline were 13°C and a low light level (±3–5 mol m^-2 s^-1). When the pre-storage conditions were normal growth room conditions (24°C and 30 mol m^-2 s^-1), in vitro cultures could be stored for 18 months. With the most favourable pre-storage treatment (18°C and 15 mol m^-2 s^-1) some cultures still had green shoots after 36 months of storage, but did not survive transfer to peat/perlite.Pre-conditioning before storage was most favourable for Nephrolepis, and not that important, but still favourable, for Cordyline. There was an interaction between pre-storage temperature and pre-storage irradiance. For both species a high irradiance level was less favourable than a low irradiance level when combined with high growth room temperatures.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic acid - NOA 2-naphthoxyacetic acid     

Induction and Repression of CAM in Sedum telephium L. in Response to Photoperiod and Water Stress

Lee, H. S. J. and Griffiths, H. 1987. Induction and repressionof CAM in Sedurn relephluni L. in response to photopcnod andwater stress.—J. exp. Bot. 38: 834–841. The introduction and repression of CAM in Sedurn telephiunmL, a temperate succulent, was investigated in watered, progressivelydrouglited and rewatered plants in growth chambers. Measurementswere made of water vapour and CO₂ exchange, titratable acidity(TA) and xylem sap tension. Effects of photoperiod were alsostudied. CAM was induced by drought under long or short days,although when watered no CAM activity was expressed. C₃-CAM intermediate plants were used for the investigation ofwater supply. Those which had received water and those drought-stressedboth displayed a similar nocturnal increase in TA, with a day-nightmaximum (H+) of 69 µmol g^–1 fr. wt. The wateredplants took up CO₂ at a maximum rate of 2?2 µmol m^–2s^–1 only in the light period, while the droughted plantsshowed a maximum nocturnal CO₂ uptake rate of 0?69 µmolm^–2 s^–1. Subsequently, as CAM was repressed, thewatered S. telephiwn displayed little variation in TA, withconstant levels at 42 µmol g^–1 fr. wt. (day 10).After 10 d of drought stress, the CAM characteristics of S.telephiurn were aLso affected, with reduced net CO₂ uptake andH+. The transition between C₃ and CAM in S. telephium can be describedas a progression in terms of the proportion of respiratory CO₂which is recycled and refixed at night as malic acid, in comparisonwith net CO₂ uptake. Recycling increased from 20% (day 1) to44% (day 10) as a result of the drought stress and was highin both the CAM-C₃ stage (no net CO2 uptake at night) and alsoin the drought-stressed CAM stage (reduced net CO₂ uptake atnight). The complete C₃-CAM transition occurred in less than8 d, and the stages could be characterized by xylem sap tensionmeasurements: CAM = 0?50 MPa C₃-CAM = 0?36 MPa C₃ = 0?29 MPa. Key words: CAM, Sedum telephium L., recycling     

Gibberellins and Stem Growth as Related to Photoperiod in Silene armeria L

Stem growth and flowering in the long-day plant Silene armeria L. are induced by exposure to a minimum of 3 to 6 long days (LD). Stem growth continues in subsequent short days (SD), albeit at a reduced rate. The growth retardant tetcyclacis inhibited stem elongation induced by LD, but had no effect on flowering. This indicates that photoperiodic control of stem growth in Silene is mediated by gibberellins (GA). The objective of this study was to analyze the effects of photoperiod on the levels and distribution of endogenous GAs in Silene and to determine the nature of the photoperiodic after-effect on stem growth in this plant. The GAs identified in extracts from Silene by full-scan combined gas chromatography-mass spectrometry (GC-MS), GA₁₂, GA₅₃, GA₄₄, GA₁₇, GA₁₉, GA₂₀, GA₁, GA₂₉, and GA₈, are members of the early 13-hydroxylation pathway. All of these GAs were present in plants under SD as well as under LD conditions. The GA₅₃ level was highest in plants in SD, and decreased in plants transferred to LD conditions. By contrast, GA₁₉, GA₂₀, and GA₁ initially increased in plants transferred to LD, and then declined. Likewise, when Silene plants were returned from LD to SD, there was an increase in GA₅₃, and a decrease in GA₁₉, GA₂₀, and GA₁ which ultimately reached levels similar to those found in plants kept in SD. Thus, measurements of GA levels in whole shoots of Silene as well as in individual parts of the plant suggest that the photoperiod modulates GA metabolism mainly through the rate of conversion of GA₅₃. As a result of LD induction, GA₁ accumulates at its highest level in shoot tips which, in turn, results in stem elongation. In addition, LD also appear to increase the sensitivity of the tissue to GA, and this effect is presumably responsible for the photoperiodic after-effect on stem elongation in Silene.     

Development in vitro of Nephrolepis exaltata cv. Bostoniensis Runner Tissues

Study of organogenesis in vitro in runner tissues of the fern Nephrolepis exaltata cv. Bostoniensis has shown that the process involves two stages: the first being primoirdium initiation and the second involving release of these primordia from an apparent quiescent state. In vitro shoot development from the primordia required light and an exogenous supply of carbohydrate. No exogenous growth regulators were necessary, but rate of shoot development was promoted by both NAA and kinetin. Root initiation occurred in both the light and dark and was promoted by 2,4-D and NAA, but neither was essential. Organogenesis was generally inhibited with standard levels of Murashige and Skoog inorganic salts, but inhibition could be avoided with the use of dilute levels.     

Effect of Photoperiod on Vegetative Growth in Two Natural Populations of Dactylis glomerata L.

The growth of two natural populations of cocksfoot from contrastingclimatic regions (Norway and Portugal) was studied at four temperaturesand two photoperiods. Serial harvests were taken and quadraticcurves were fitted to log dry weight and leaf area for eachreplicate in order to calculate growth attributes at a constantplant weight for all treatments. Interactions of population,temperature, and photoperiod on relative growth-rate (RGR) werefound, with the greatest population differences at 5 and 30°C in an 8-h photoperiod. Leaf-area ratio (LAR) played alarger part than net assimilation rate (NAR) in determiningthe differential population responses in RGR to daylength, andthese differences in LAR were primarily the result of differentpatterns of dry-matter distribution within the plant.     

The Effects of Temperature and Photoperiod on the Onset of Summer Dormancy in Poa bulbosa L.

Poa bulbosa L. plants became dormant in long days (16 h), whilein short days (8 h) they remained non-dormant for extended periods.Morphologically, the onset of dormancy was expressed by theformation of a true bulb at the base of every tiller, by thecessation of tillering and leaf emergence and, finally, by thedrying-up of the leaves. Low temperature delayed the onset ofdormancy but did not prevent it. This effect of temperaturemay explain the delayed onset of dormancy observed in naturalpopulations under a cool climate at a hilly habitat, comparedto plants growing under a warmer climate, at a lower, coastal-plainhabitat. Dormancy could be induced under short days by pre-exposureof the plants to a limited number of long days. The responsewas proportional to the number of long days given. The adaptivesignificance of the results for plant survival in a Mediterraneanclimate is discussed. Poa bulbosa L., summer dormancy, photoperiod, temperature, leaf emergence, bulbs, tillers     

Photoperiod and fur lengths in the arctic fox (Alopex lagopus L.)

Pelage is seasonally dimorphic in the Arctic fox. During the winter, fur lengths for this species are nearly double similar values taken during the summer season. Considerable site-specific differences in fur length are noted. In general, body sites which are exposed to the environment when an Arctic fox lies in a curled position show greater fur lengths in all seasons and greater seasonal variations than body sites that are more protected during rest. Well-furred sites may tend to conserve heat during periods of inactivity, and scantily furred sites may tend to dissipate heat during periods of exercise. The growth of winter fur may compensate for the severe cold of the arctic winter. Changes in fur lengths indicate a definite pattern in spite of individual variations. During the fall months, fur lengths seem to lag behind an increasing body-to-ambient temperature gradient. Both body-to-ambient temperature gradients and fur lengths peak during December through February. From March through June, gradual environmental warming is accompanied by a decrease in average fur lengths. Thus, there appears to be a remarkable parallel between the body-to-ambient temperature gradient and the fur lengths. The growth of fur in the Arctic fox parallels annual changes in ambient temperature and photoperiod.Presented at the Eighth International Congres of Biometerorology, 9–14 September 1979, Shefayim, Israel.     

Female Fertility and Mating Type Distribution in a South African Population of Fusarium subglutinans f. sp. pini

Fusarium subglutinans f. sp. pini is the causal agent of pitch canker disease of pines. The initial occurrence of F. subglutinans f. sp. pini in South Africa was limited to a single nursery, and isolates from this population are capable of reproducing sexually. We determined the effective population number, N_e, of this population by using mating type and male/hermaphrodite polymorphisms as indicators. The effective population number for mating type, N_e(mt), is 99% of the count (total population), and that for male/hermaphrodite status, N_e(f), is 42 to 46% of the count (total population). The number of strains that can function as the female parent limits the effective population number of this population. If this population is stable, then, depending upon assumptions about mutation and selection, sexual reproduction need occur only once per 26 to 153 asexual generations to maintain this level of sexual fertility.     

Photoperiod and diel variations of serum cortisol, thyroxine and protein in goldfish, Carassius auratus L.

Goldfish Carassius auratus L., were held for 1 month on one of four different photoperiods. In those groups with diel variations of serum cortisol and thyroxine (approximately 60%) the variations were entrained to the photoperiod; peak titres occurred around light onset, minimum titres at light offset. Fish held on two of the photoperiod regimes had diel variations in serum protein, however, the pattern was not consistent in relation to any aspect of the photoperiod.     

Effects of Temperature and Photoperiod on Growth and Development of Tillers and Rhizomes in Poa pratensis L. Ecotypes

The vegetative growth of four Norwegian ecotypes of Poa pratensisL. was compared at day/night temperatures of 21/12, 21/6, 12/12and 12/6 °C and at photoperiods of 12, 16, 20 and 24 h,the irradiation being approximately equal in all treatments.Tillering within tufts was most abundant in short days and atthe large temperature amplitude. Rhizome formation and elongationwere stimulated by long days and, more strongly, by high daytemperature, but a greater proportion of the rhizomes formedaerial tillers in short days. Long day stimulation of heightgrowth and dry matter accumulation differed between ecotypesbut was generally most pronounced at low temperatures. The NorthNorwegian ecotype ‘Lavang’ had a higher relativegrowth rate and developed two to three times as many rhizomesas its South Norwegian counterparts. Day/night temperature, growth rate, leaf area, photoperiodicity, Poa pratensis L., rhizomes, roots, smooth meadow grass, tillering, weight gain     

Organic acids in the rhizosphere of Banksia integrifolia L.f.

Water leachates of the proteoid root layer of a mature stand of Banksia integrifolia were analysed for low molecular weight (LMW) organic acids by GC, HPLC and colorimetric techniques. Large amounts of organic acids (2500 g in 100 mL of leachate) were found in the proteoid root layer compared to the surrounding soil and leaf litter (230 g in 100 mL of leachate). Citric acid represented approximately 50% of the total organic acids leached, malic acid approximately 18%, and aconitic acid constituted approximately 17%. Concentration of citric acid in the proteoid root layer may enhance the availability of phosphorus for plant uptake.     

Rapid micropropagation for Mucuna pruriens f. pruriens L.

A rapid micropropagation system was developed for Mucuna pruriens f. pruriens using explants from 1-week-old aseptically grown seedlings. Multiple shoot regeneration occurred following an initial callus growth on Revised Tobacco (RT) medium supplemented with 2.7 M NAA and 9.8 M 2iP. Maximum number of shoot regeneration was achieved only from seedling explant 6 to 7 days old. More than 90% of the regenerated shoots could be rooted on half-strength liquid RT medium supplemented with 2.7 M NAA. Plantlets readily adopted to greenhouse conditions. This system provides a new tool for micropropagation of Mucuna pruriens f. pruriens, an important medicinal plant.Abbreviations BAP 6-benzylaminopurine - Kn kinetin - 2iP 2-isopentenyladenine - AdS adenine sulphate - NAA alpha-naphthalene acetic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - MS Murashige and Skoog (1962) medium - RT Revised Tobacco medium (Kaul and Staba, 1968)     

Effects of Temperature and Photoperiod on Flowering in Chickpeas (Cicer arietinum L.)

Factorial combinations of two photoperiods (12 and 15 h), threeday temperatures (20, 25 and 30 °C) and three night temperatures(10, 15 and 20 °C) were imposed on nodulated plants of ninechickpea genotypes (Cicer arietinum L.) grown in pots in growthcabinets. The times to first appearance of open flowers wererecorded. For all genotypes, the rates of progress towards flowering(the reciprocals of the times taken to flower) were linear functionsof mean temperature. There were no interactions between meantemperature and photoperiod but the longer photoperiod increasedthe rate of progress towards flowering. These effects were independentof both radiation integral (the product of irradiance and photoperiod)and the vegetative stature of the plant. Taken in conjunctionwith evidence from work on other long-day species, it is suggestedthat the photo-thermal response of flowering in chickpeas, overthe range of environments normally experienced by the crop,may be described by the equation: 1/f = a+b