STUDIES ON THE FORMATION AND SPROUTING OF AERIAL TUBERS IN BEGONIA EVANSIANA ANDR. VIII. DUAL EFFECT ON TUBERIZATION OF NEAR INFRARED LIGHT GIVEN IN DARK PERIODS

This preliminary report describes how the formation of aerialtubers of Begonia evansiana in response to short-days is inhibitedby near infrared irradiations given before and during dark periods.The time of application of red light during the dark period,which caused the maximum inhibition, was found to have no relationto the day. length while that of near infrared light causingthe same effect shifted from an early to a later part of thedark period as daylength was shortened. It was also observedthat the effect of near infrared light given before the darkperiod was inhibitive when the photoperiod was short, and somewhatpromotive when the latter was long. (Received October 31, 1962; )     

The Effect of Length of Dark Period on the Amplitude of Leaf Movement in Bauhinia monandra

In Bauhinia monandra, a short-day plant with a critical daylengthfor flowering of about 12 hours, there is a progressive decreasein the amount of nastic leaf movement as daylength increases.When the daylength is increased from 18 to 18.5 hours, however,there is such a sudden decrease as to suggest the existenceof a critical dark period at that daylength. The parallel withthe critical dark period in the photoperiodism of some short-dayplants lends some support to Bünning's endogenous rhythmexplanation of photoperiodism. All the same, in Bauhinia thesame rhythm cannot very well control both leaf movement andphotoperiodic response, for the observed critical daylengthsdo not agree.     

STUDIES ON THE FORMATION AND SPROUTING OF AERIAL TUBERS IN BEGONIA EVANSIANA ANDR. X. TUBERIZATION UNDER LONG-DAYS AND IN DARKNESS

1. Aerial tuber formation of Begonia evansiana Andr. known totake place usually in response to short-day conditions occurredalso under long-day conditions, provided a part of the photoperiodswas maintained at a lower temperature (chillng). Such a changeof the critical daylength was marked in degree when the chillingtemperature was from 9° to 13°. The effectiveness ofthe chilling was more pronounced when it was given during thelater part of photoperiods, namely, just before nyctoperiods,than when given during the early part. No promotion of the chillingeffect by sugar application was found. 2. If the plant was previously subjected to chilling under illumination,aerial tuber formation occurred in continuous darkness. Themagnitude of this dark tuberization increased with decreasingthe temperature and with prolonging the duration of the chilling. 3. If the plant was previously exposed to chilling, aerial tuberformation occurred in response to a single photoperiodic cycle,whose critical dark length was shorter than that in the standardcondition. The magnitude of the tuberization was increased withthe prolongation of the chilling period. The effectiveness ofthis previous chilling survived over one day even under illuminationand a temperature of 30°. In a plant unexposed to the chilling,tuber formation required at least two cycles of short-days. 4. The aged plant which is known to tuberize in darkness wasunable to respond to a single short-day. 5. Upon a modification of Gregory's scheme of the process ofshort-day response, the above findings were inclusively explained. (Received August 2, 1963; )     

The Effects of Light Breaks in the Dark Period on Flower-bud Development in Varieties of Phaseolus vulgaris L.

A light break imposed in the middle of, or more effectively,two-thirds of the way through a 13 h dark period inhibited thedevelopment of the first initiated flower buds and reduced theproduction of open flowers in two daylength-sensitive varietiesof Phaseolus vulgaris. The effects were similar to those ofa long photoperiod applied continuously and therefore provideclear evidence of the importance of the dark period in mediatingthe effects of daylength on flower-bud development in the twovarieties. Phaseolus vulgaris, bean flower-bud development, photopcriodism     

The Effects of Brown Rust and Phosphate on Cold Acclimation in Winter Barley

The green leaf area of winter barley, cv. Sonja, sampled fromthe field at different times during winter was always greatestin plants grown at high soil phosphate and smallest in plantsgrown at low soil phosphate, and at each fertilizer level wasgreater in healthy plants than in plants infected by rust (Pucciniahordei). In leaves that survived the coldest period of winter,the percentage area that was damaged was increased by rust infectionwhich prevented the ameliorating effects of high soil P. Rustand low P interacted to reduce the increases in leaf area andshoot d. wt that occurred when higher temperatures prevailedin spring. Under controlled conditions in the laboratory, phosphate reducedthe injury suffered when plants not acclimated to low temperatureswere exposed to freezing conditions, but this effect was removedby rust infection. After rust infection, freezing temperatureswere damaging even to acclimated plants, particularly if grownwith low soil P. Evidence of visible symptoms, and quantitativemeasurements of electrolyte efflux from intact leaves, chlorophyllfluorescence in vivo, and ethane and ethylene evolution fromcold-acclimated plants, showed that infection raised the minimumtemperature at which tissues could survive without injury. Infectedleaves were more sensitive to low temperature post-sporulationthan presporulation. Measurements of electrolyte efflux andchlorophyll fluorescence on plants growing under cold conditionsshowed that infection inhibited the processes of acclimationto low temperatures. Winter barley, Puccinia hordei, injury, low temperature, acclimation     

Studies in Dormancy of Sycamore: II. THE EFFECT OF DAYLENGTH ON THE NATURAL GROWTH-INHIBITOR CONTENT OF THE SHOOT

1. An investigation was made into effect of daylength conditionsof the inhibition content of first-year seedlings of sycamore(Acer pseudoplatanus). 2. The shoot apical regions and mature leaves were extractedwith 80 per cent. Aqueous methanol, fractionated by paper chromatographyin isopropanol/ammonia and assayed by the wheat-coleptile growthtest. 3. A growth inhibitor was present in all extracts at R_f 0.7.Higher levels of inhibitor were present in both apices and matureleaves of plants transferred to short-day conditions than ofthose maintained under long-days throughout. 4. These difference in inhibitor level can be detected after2–5 days of short-day treatment, Preceding any markedeffect of daylength on growth. 5. Evidence is adduced in support of the hypothesis that theinhibitors is produced in the leaves during darkness and istransported to the apex during the photoperiod.     

Studies on the Expansion of the Leaf Surface: II. THE INFLUENCE OF LIGHT INTENSITY AND DAYLENGTH

The parts played by constant amounts of visible radiation perday and its two components—daylength and intensity—ininfluencing the growth of Cucumis sativus have been investigated.The amount of radiation per day had a far greater influencethan either of its components per se. Nevertheless, small significanteffects of photoperiod were found, leaf expansion and dry weightincrease being greatest at daylengths between 10 and 15 hr.rather than with longer days which, with similar daily totals,would be expected to give the greatest amounts of assimilation. Rates of leaf production and appearance were greatest with thehighest amounts of radiation, but the rates of expansion ofindividual leaves and their maximum areas were greatest withintermediate amounts of radiation. This response resulted inan optimum curve relating the leaf surface and the dry weightattained after a given period to radiation. The amount of radiationgiving the maximum leaf surface and dry weight decreased withage and with external nutrient supply, but at any one age washigher for increase in dry weight than for increase in leafsurface; stem and root tissues responded more to high radiationthan did the leaf surface. The net assimilation rate was a linearfunction of visible radiation over the range of 15–120cal. cm.^-2 day^-1 explored, the highest value of radiation usedrepresenting the intensity at which photosynthesis would beexpected to be maximal over a 12–15 hr. day. The inhibitory effect of high radiation on leaf expansion andthe resultant influence on the growth of the plant are explainedin terms of the number and intensity of ‘sinks’for carbohydrate and mineral nutrients within the plant.     

Developmental and photobiological factors affecting photoperiodic induction in Arabidopsis thaliana Heynh. Landsberg erecta

We have tested whether the promotion of flowering by long days(LD) in Arabidopsis thaliana is a consequence of photoperiodicinduction. To achieve this, the flowering responses of Arabidopsisthaliana (L.) Heynh. Landsberg erecta (Ler) and the long-hypocotylmutants hy2, hy3 and hy4 were determined with respect to age,daylength and light quality. Ler was capable of distinguishingbetween short days (SD) and long days (LD) from about 4 d aftersowing at 20 C, the time at which cotyledons were expandingand greening. At this stage, the critical daylength was between8 h and 10 h. At 7 d, seedlings required five LD for inductionand, as the seedlings aged, they became more sensitive so thatby day 20, one LD was fully inductive. The response to SD innewly germinated seedlings was to delay flowering without alteringleaf number, but after about 10 d, delay of flowering by SDwas accompanied by extra leaves. In light quality experiments,blue light (B) was inductive for 5-d-old plants and in all subsequenttreatments, far-red (FR) caused induction in treatments at 12d and 18 d and low pressure sodium, equivalent to red, was notinductive at 5 d and 12 d, but partially inductive at day 18.Hence, both a specific blue-light photoreceptor and phytochromeA in High Irradiance Response mode promote floral induction.In daylength transfer experiments all three hy mutants respondedto LD by earlier flowering. Both hy2 and hy3 produced substantiallyfewer leaves than Ler in SD and hy3 flowered slightly earlierthan Ler. The hy4 mutants flowered later than Ler in SD andhad a higher leaf number. A scheme is proposed in which photoperiodicinduction depends on the ability of the plant to sense photoperiod,the stage of development and the photobiological input. We alsopropose that phytochrome A and the blue photoreceptor promoteflowering whereas phytochrome B promotes vegetative development. Key words: Arabidopsis thaliana, blue-absorbing photoreceptor, flowering, photoperiodic induction, phytochrome     

Pre-flowering Growth and Development of the Inflorescences of Maize: I. PRIMORDIA PRODUCTION AND APICAL DOME VOLUME

The growth and development of the main stem and the two uppermostaxillary apices of maize were studied during the period fromemergence until flowering. Plants were grown in the field undervarying levels of applied nitrogen fertilizer at two times ofsowing. The effects of daylength were isolated from those oftemperature by making comparisons of growth and developmenton a thermal time basis. The growth and development of the terminal (male) apex and thetwo uppermost axillary (female) apices followed the same patterns,with apex volumes increasing curvilinearly with increase innumber of leaf or husk primordia. The RGR(relative growth rateof volume) of the terminal apex was, however, only approximatelyone-tenth of the axillary apices. There was no difference ingrowth and development between the first and second axillaryapices before flowering: other factors, such as accumulationof dry weight, rather than primordia production, must be responsiblefor an axillary apex's potential to bear grain. Applied N, andto a lesser extent short days, increased the rates of growthand development of all the apices. For example, applied N increasedthe RGR (volume) of the apical domes, and the rate of productionof spikelet primordia, by about 25%. All axillary apices and treatments showed a single relationshipbetween number of spikelets and surface area of the ear: a favourableenvironment (e.g. high N) simply accelerated the progressionof spikelet production and area expansion along this singlepath. We conclude that this path is probably determined geneticallyand that N and time of sowing influence potential yield of maizethrough effects on the surface area of the ear but not on thedensity of spikelets formed. Key words: Maize, inflorescence, N application, daylength, temperature, apex volume     

松毛虫卵期几种寄生蜂的共寄生现象及其对寄生率的影响

松毛虫赤跟蜂 Trichogramma dendrolimi Matsumura 白跗平腹Pseudanastatusalbitarsis Ashmead松毛虫宽缘金小蜂Pachyneuron olitarium(Harig), 松毛虫黑卵蜂 Telenomus dendrolimusi Chu和大蛾卵跳小蜂Ooenvyrtus Kuwanae(Howard)是松毛虫卵期几种主要寄生蜂。通过对上述几种寄生蜂寄生习性的研究表明：赤眼蜂和平腹小蜂不但能寄生新鲜害虫卵,还可以寄生对方已寄生并巳发育1-3天的寄生卵,但羽化串均不高;松毛虫宽缘金小蜂不寄生新鲜害虫卵,专门寄生赤眼蜂寄生后巳发育1-7,天的寄生卵,其中又以赤眼蜂发育3-5天的卵寄生串和羽化率为最高。除赤眼蜂和平腹小蜂可以混合使用外,其它蜂种混用都不同程度地存在相互排挤的现象。如果先让平腹小蜂寄生尔后再让赤眼蜂寄生或先让赤眼蜂寄生,尔后再让跳小蜂或黑卵蜂寄生,能够提高卵块寄生串和充分发挥各自天敌的作用。     

TWO LIGHT REACTIONS IN THE PHOTOPERIODIC CONTROL OF FLOWERING OF LEMNA PERPUSILLA AND L. GIBBA

The effects of light quality on the photoperiodic control inthe flowering of a SD duckweed, Lemna perpusilla strain 6746,and a LD duckweed, L. gibba strain G3, were investigated withspecial reference to the interaction between R and B or FR lights. In the diurnal alternation of R or G light and dark periods,L. perpusilla responded as a SDP, but in that of B or FR lightit was almost daylength-indifferent. On the other hand, L. gibbaresponded as a LDP under B, R or FR light, although the criticallight length was altered by the light quality. In the diurnal alternation of R and B or FR light periods containingno dark period, L. perpusilla flowered with the shortening ofthe optimal and critical R light lengths, compared with theplant exposed to that of R light and dark period. The floweringresponse of L. gibba to the R light length showed double peaks,that is, the first peak at the R duration less than 9 hours,and the second at the R duration longer than 9 hours. The firstpeak corresponds to the optimal R light length in L. perpusilla. Under the CL with a mixture of R and B or FR lights, the floweringand frond production were influenced by the intensity ratioof two light given. In both plants, the optimal ratio of B toR or FR to R for the flowering was always greater than thatfor the frond production. It is suggested that the B or FR light interacts with the Rlight in the photoperiodic process in the plants and this interactionbetween the R and B or FR lights should be of importance forobtaining a better understanding of photoperiodism. (Received August 28, 1965; )     

Studies on the vegetative life cycle of Chlamydomonas reinhardi Dangeard in synchronous culture II. Effects of chloramphenicol and cycloheximide on the length of cell cycle

Cells of Chlamydomonas reinhardi Dangeard were synchronouslygrown under a 12 hr light— 12 hr dark regime. When thesecells were brought into contact with chloramphenicol for a shortperiod at early stages in the cell cycle, zoospore liberationwas delayed for a period which was nearly the same as that ofthe duration of contact with the antibiotic. When given at laterstages, the antibiotic caused no such effect. Cycloheximide,on the other hand, caused—when provided at some intermediatestage of the cell cycle— two different prolonging effectson the length of the cell cycle: one doubled the normal length(observed when the drug was administered at certain stages)and the other caused a delay similar to that caused by chloramphenicol.Interestingly, no prolonging effect was observed when cycloheximidewas given either at early stages or at later stages, such asduring the last 1/4 period of the cell cycle preceding zoosporeliberation. Based on these results, three phases were distinguishedin the algal cell cycle: "chloramphenicolsensitive", "cycloheximide-sensitive"and "insensitive" phases. Considering the known facts aboutthe modes of action of the two antibiotics inhibiting proteinsynthesis, discussions were made on the significance of proteinsynthesis in chloroplasts and in cytoplasm in determining thelength of the cell cycle. (Received October 12, 1970; )     

DORMANCY OF GLADIOLUS CORMS VI. EFFECTS OF TEMPERATURE TREATMENT ON BREAKING DORMANCY OF GLADIOLUS CORMS STORED IN A STORAGE ROOM AND OF THOSE GROWN UNDER DIFFERENT DAY-LENGTH

A high temperature treatment at 35? for 5 days followed by alow temperature treatment at 0-5? for 25 days was given at fifteen-dayintervals to five groups each of two varieties (White Gold andCardinal Prince) stored in a storage room from September 27to November 26. The temperature treatment was apparently effectivefor sprouting of corms of both varieties at earlier period,but rather inhibitory at later period of dormancy. The plants of two varieties (Early Red and Spot Light) grownunder short day-length (9 hr) showed slightly earlier floweringand corm-forming than those grown under natural long day-length.These plants were harvested from July 1 to Septmber 1 at twentydayintervals, and sprouting of their corms with and without temperaturetreatment similar to the previous method was investigated. SpotLight corms did not sprout irrespective of temperature treatment.Early Red corms always sprouted earlier in the temperature-treatedlots, whereas they sprouted a little later in the non-treatedlots. The temperature treated corms grown under the short day-lengthshowed delaying and low percentage of sprouting. On the contrary,in the non-treated lots, sprouting of corms grown under thelong day-length was slower than those grown under the shortday-length. ¹Contribution No. 24 from Laboratory of Horticulture (Olericultureand Floriculture), Kyoto University. (Received May 23, 1960; )     

Pathway of dark inorganic carbon fixation in two species of diatoms: influence of light regime and regulator factors on diel variations

Planktonic algae submitted to vertical mixing with a short periodicitycommute many times a day from low to high irradiance levels.To study the influence of this light periodicity, two diatoms,Skeletonema coslatum and Nitzschia turgiduloides, were cultivatedunder alternating conditions of 2 h light/2 h dark (2 h/2 h),simulating vertical mixing in the natural environment. Two otherlight regimes were used: continuous light (CL) and alternatecycles of 12 h light/12 h dark (12 h/12 h). Products synthesizedin the dark by S.costmum during 60 s incubation for 2 h/2 hculture or during 5 min for 12 h/12 h culture were determined.They were essentially sugars, malate, aspartate and glyceratefor 2 h/2 h cells and 12 h/12 h cells taken at the beginningof the light period. In contrast, 12 h/12 h cells taken duringthe darkness or in the middle of the light period and set inthe dark synthesized only amino acids. Our results corroborateprevious reports on dark CO₂ fixation via phosphoenolpyruvatecarboxykinase (PEPCKase, enzyme allowing the fixation of CO₂on PEP and the synthesis of amino acids) with involvement ofa substrate synthesized during the light period, but demonstratethat incorporation also occurs by the C-3 pathway (pathway responsiblefor the major CO₂ fixation in the light) in the very early stagesof the dark period. Another important result highlighted bythis study is the appreciable rate of dark fixation: on average6.7, 8.3 and 12.7% of photosynthesis at saturating photon fluxdensity for N.turgiduloides cultivated under 2 h/2 h, CL and12 h/12 h regime respectively and nearly 12% for S.costatumin the 2 h/2 h light regime. Variation of dark fixation wasinvestigated as a function of hour in the two species. Skeletonemacostatum cells submitted to the 2 h/2 h cycle show a constantrate of light-independent assimilation throughout the day. Bycontrast, both N.turgiduloides grown under the 12 h/12 h or2 h/2 h regime and S.costatum cultured under the 12 h/12 h cycleundergo fluctuations in the rate of dark fixation over the light/darkcycle. The mean dark fixation rate is controlled by the lengthof the photoperiod or the frequency of light fluctuations, dependingon species. We argue that this phenomenon must be taken intoconsideration in primary production calculations. Dependingon whether they are synthesized at the beginning or at the endof the light period, products are somewhat different and therate of fixation varies. This leads us to suggest that the pathwayof dark fixation may be regulated by at least two factors: amountof available substrate and enzyme (RuBPCase and PEPCKase) activityand/or amount.     

Effects of Photoperiod on the Apparent Viscosity of Leaf Cytoplasm in Kalanchoe blossfeldiana: 2. Some Long- and Short-term Effects of Daylength and Spectral Composition of Light

The effects of a range of daylength treatments upon the apparentviscosity of the mesophyll cytoplasm were tested in Kalanchoeand some other daylength-sensitive species by means of a centrifugationtechnique. In Kalanchoe, apparent viscosity increases with increasingshort-day induction, the rise being rapid initially but fallingoff subsequently in the same way as the flowering response.Since the response to light-break treatment is equivalent tolong-day conditions, the effect is truly photoperiodic. Theshort-day increase appears to be only partially reversible uponreturn to long-days. Single leaves may be treated and the effect is not translocatedto the opposite member of a leaf pair. The immediate response to change from light to dark and viceversa is oscillatory; e.g. in the dark an initial fall is succeededby a steep rise and then a more gradual fall in apparent viscosity. Light-breaks with red light are equivalent to white light, andthose with far-red light to darkness. No reversal of red effectsby far-red light has yet been demonstrated. In other species tested, apparent viscosity was significantlyhigher under short-day in Chrysanthemum and Michaelmas Daisy,and under continuous light in Epilobium, i.e. in the daylengthswhich induce flowering. The results are discussed in relationto the present theories of photoperiodism.     

EFFECT OF TWILIGHT ON PHOTOPERIODIC INDUCTION IN SOME SHORT DAY PLANTS

Light-sensitivity of the first and the last processes in theinductive dark period, and the effect of twilight on photoperiodicinduction were investigated with four short day plants. In Oryza sativa (Akebono), the first and the last processesare relatively light-insensitive, and the photoperiodicallyeffective day length under natural conditions is consideredto be equal to the astronomical day length. In Biloxi soybean and Perilla frutescens, the first processis re latively light-insensitive, but the last process is moresensitive. Effective dark period seems to begin when twilightis 50200 lux in the evening and continue until it is about 10lux in the morning. In Xanthium saccharatum, both the first and the last processesare relatively light-sensitive, but the former is more sensitivethan the latter. Effective dark period seems to begin when twilightis 110 lux in the evening and continue until it is 1050 luxin the morning. ¹Present address: Laboratory of Genetics and Plant Breending,Faculty of Agriculture, University of Osaka Prefecture, Sakai-City,Osaka. (Received February 17, 1961; )     

Studies on the Expansion of the Leaf Surface: IV. THE CARBON AND PHOSPHORUS ECONOMY OF A LEAF

The fixation, utilization, and translocation of carbon and thenet import and export of phosphorus by three leaves of Cucumissativus over the course of their lives were measured in a controlledenvironment. The rate of photosynthesis of a leaf followed a regular dailypattern, rising to a maximum during the first 2 hrs. of thelight period and subsequently falling. Dark respiration wasusually highest at the beginning of the dark period and fellthroughout it. The daily rate of photosynthesis per unit areaof a leaf fell during its later life partly as a result of shadingby upper leaves and also because of an independent age factor.The rate of dark respiration per unit area was high in veryyoung leaves but fell rapidly with age. The amount of phosphorus in each leaf reached a maximum beforethe leaf had reached its maximum dry weight. There was thensubstantial net loss of phosphorus from the leaf. The changing function of each leaf as a sink or source of carbohydrateand mineral nutrients was determined. Four stages were recognized:(1) early development from inception until some time after unfolding,when the leaf was dependent upon imported carbohydate; (2) aperiod of rapid expansion, associated with a high rate of uptakeor mineral nutrients, during which translocation of assimilatedcarbon from the leaf was most rapid; (3) a time of decliningrates of growth, photosynthesis and export of carbon, associatedwith substantial loss of phosphorus; (4) finally, a short sensescentphase with net loss of CO₂, terminating in the death of theleaf.     

Diurnal change of light-dependent uridine incorporation into RNA in a long-day duckweed, Lemna gibba G3

Light-dependent incorporation during subjective day and nightof radioactive uridine into RNA of a long-day duckweed, Lemmagibba G3, was examined. When the dark treatment was startedfrom the subjective night phase, the activity of uridine incorporationdropped approximately by half only after the very subjectivenight phase had passed or with the commencement of the subsequentsubjective day phase. However, when the dark treatment was startedfrom the subjective day phase, the incorporating activity promptlybegan to decrease and the inhibition increased with the lengthof the dark period until a final steady level (also at ca. 50%of the initial level) was reached after 24 hr of darkness. Thesetwo phases of different light sensitivities recurred daily undercontrol of the physiological clock and the rhythm was resetby a light-on signal. The lowered incorporating activity dueto the darkened day phase was recovered completely by a 12-hror even 15-min white light period perturbing the succeedingnight phase. That the incorporation of uridine in every RNAspecies, especially in chloroplast ribosomal RNA, was loweredby dark treatment of the day and night phases, was disclosedby MAK column chromatography and acrylamide gel electrophoresis. (Received August 21, 1974; )     

Flower Opening in Asiatic Lily is a Rapid Process Controlled by Dark-light Cycling

In commerce, Asiatic lilies are picked in bud, each stem holdingseveral buds. We found flower opening was rapid, taking lessthan 4 h both on the stem and for excised buds. Opening wasalso strongly synchronous. For a 12 h day-night cycle, openingbegan late in the dark period, reaching a mid-point after 11h of darkness. This was equally true of buds that were excisedwhen nearly ready to open, and those with 3–4 d of developmentto complete. Reversing day and night reversed the time of opening,and red light was as effective as white light in providing ‘day’conditions. A 15 min light break during the night did not affectthe opening. Lengthening the night (8, 12, 16 h) and shorteningthe day delayed opening from 9, to 11, to 13 h after the startof darkness, respectively. In continuous light and continuousdark, synchronicity was lost. If opening flowers were held inextended darkness, two phases of opening could be discriminated.In a ‘dark phase’, petals opened to approx. 40°,and anthers remained intact. When such flowers were returnedto light, there was a ‘light phase’, where petalsopened further, became more pigmented and began to recurve,and the anthers dehisced, these events taking only 2–3h. The net result was that flowers became fully open and anthersdehisced approx. 2 h after dawn, regardless of daylength. Copyright2000 Annals of Botany Company Asiatic lily, Lilium hybrid, flower opening, timing, endogenous rhythm, synchronicity