The Effect of Temperature on the Production and Abscission of Flowers and Pods in Snap Bean (Phaseolus vulgaris L.)

The effect of temperature on production and abscission of flowerbuds, flowers and pods was studied in a determinate snap-beancultivar (cv. Tenderette). Under moderate temperature (e.g.27/17 °C) the onset of pod development was associated withcessation of flower bud production and with enhanced abscissionof flower buds. Raising night temperature from 17 °C to27 °C strongly reduced pod production, mature pod size andseeds per pod, while an increase in day temperature from 22°C to 32 °C had smaller and less consistent effects.Pod production under high night temperature was not constrainedby flower production since 27 °C at night promoted branchingand flower bud appearance. Under 32/27 °C day/night temperaturethe large reduction in pod set was due to enhanced abscissionof flower buds, flowers and young pods (< 3 cm). Flowershad the highest relative abscission followed by young pods andflower buds. Therefore, the onset of anthesis and of pod developmentwere the plant stages most sensitive to night temperature. Podslarger than 3 cm did not abscise but usually aborted and shrivelledunder high night temperature. The effects of 32/27 °C werenot due to transient water stresses and were observed even undercontinuous irrigation and mist-spraying. High temperature, flower production, pod set, seed set, abscission, snap bean, Phaseolus vulgaris L., cv. Tenderette     

Seed Germination in Amaranthus retroflexus L. as Affected by the Photoperiod and Age During Flower Induction of the Parent Plants

Seed germination in Amaranthtis retroflexus, a facultative shortday plant, was affected by the parental photoperiodic conditions.Seeds from parents grown continuously in short days (SD, 8 h)had a higher dark germination and a greater response (at 30°C) to a short irradiation or low temperature pretreatmentthan seeds from plants grown continuously in long days (LD,16 h). Daily night breaks of 1 h in the middle of the long-nightinhibited the SD induction of flowering as well as the SD promotionof germinability. Germinability of seeds produced by plantsinduced to flower in LD by 1, 2, or 3 SD was lower than thatof seeds produced by plants grown continuously in SD, and decreasedwith the age of the parent plants at the time of flower induction.     

Consequences of climate and body size on the foraging performance of seed‐eating ants

1. Changes in climatic factors could have major effects on the foraging performance of animals. To date, however, no study has attempted to examine the concurrent effect of different climatic factors on foraging performance of individual organisms. 2. In the present study, this issue was addressed by studying changes in foraging performance of seed‐eating ant colonies of the genus Messor in response to variation in precipitation and ambient temperature along a macroecological gradient. In addition, we examined the way three colony‐level attributes, foraging distance, forager number, and variance in worker‐size, could affect foraging performance in those ants. Foraging performance was measured as size matching, i.e. the correlation between forager size and load size. The study was carried out for 2 years in six sites along a south‐north productivity gradient in a semi‐arid region of the Eastern‐Mediterranean. 3. Size matching increased with increased precipitation as well as with an increase in worker‐size variability, but slightly decreased with increasing temperatures, as predicted by foraging‐decision models. In contrast, foraging distance had no effect on size matching. Interestingly, size matching showed a unimodal relationship with forager number. 4. These results indicate that interplay between climate and body size affects foraging performance either directly via physiological constraints, or indirectly through their effect on food availability. Moreover, this is one of the first evidences to support the assumption that ant colonies can differ in their ability to optimally allocate their workforce in natural environments. This emphasises the importance of studying the way foraging strategies vary across environmental gradients at macroecological scales.     

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     

The role of the leaves in the regulation of internode elongation in Phaseolus vulgaris

Time-course patterns of leaf and internode elongation were studied in bean plants. Each leaf started its main elongation period when the leaf below reached half of its final length. The onset of leaf unfolding was nearly synchronous with the initiation of the elongation of the subjacent internode. Excision of young leaves increased the rate of stem elongation as a result of an earlier unfolding of the next upper leaves and the concomitant advancement in the elongation of their subjacent internodes. IAA or NAA (1% in lanolin) suppressed the enhancement effects of leaf excision on leaf and internode elongation. The excision of a young leaf increased the final length of internodes located below it, and at the same time decreased the final length of the internodes located above the excised leaf. The reduction was greater the younger the internode. Differences in internode elongation after leaf excision were related to changes during internode ontogenesis in their relative response to the availability of assimilates on the one hand, and on the other hand to hormonal factors transported acropetally from the young leaves to the growing internodes.     

Analysis of Regrowth Patterns and Carbohydrate Levels in Lolium multiflorum Lam.

The regrowth pattern in Lolium multiflorum was analysed in relationto carbohydrate levels and developmental characteristics, usingtwo contrasting populations. Liscate (a natural population collectedin Northern Italy) and the cultivar S 22, the former havingmore erect tillers, longer leaves and a lower rate of leaf appearance.The plants were grown in 16 h photoperiods, at 15/10 °C.NAR was lower in S. 22, but because LAR was higher as a resultof the greater SLA, the RGR was similar in Liscate and S. 22Starch levels were also similar in the two populations, butthe level of WSC was higher in Liscate than in S 22. When thetwo populations were defoliated to the same extent, total leafregrowth and rate of leaf elongation were greater in Liscate,but its tillering was more inhibited. Although the rates ofleaf regrowth were eventually similar in both populations, theywere initially lower in S. 22, leading to a higher total regrowthin Liscate. In both populations, WSC levels in the roots andstubble decreased after defoliation, but starch levels remainedunchanged. During regrowth in the dark, starch levels also decreased,but only when most of the WSC in the stubble was depleted. Lolium multiflorum Lam, Italian ryegrass, relative growth rate, net assimilation rate, leaf area ratio, specific leaf area, leaf weight ratio, carbohydrate     

Initiation, Orientation and Early Development of Primary Rhizomes in Sorghum halepense (L.) Pers.

Axillary buds on the most basal portion of the seedling shootof Sorghum halepense differentiate directly into rhizome buds.The initial orientation of these buds is upwards, but this orientationstarts to be reversed almost immediately. The reversal is causedby the combined effect of differential radial expansion of thebasal internodes immediately above and below the bud, and differencesin the extent of mitotic activity on the abaxial and adaxialsides of the bud. Reorientation is a geotropic and is progressivelyless with acropetal nodal position of the bud. Further growthof the rhizomes proceeds in the same orientation as that ofthe bud from which they had developed, until they change theirorientation again by exhibiting diageotropic, or negativelygeotropic responses. The second reorientation coincides moreor less with the onset of flowering and it exhibits a positionalgradient, such that the change is more extensive the higherthe nodal position of the rhizome. Sorghum halepense, rhizome, geotropism, morphogenesis, perennial weeds     

The Effect of Temperature on the Production and Abscission of Flowers and Pods in Snap Bean (Phaseolus vulgaris L.)

The effect of temperature on production and abscission of flowerbuds, flowers and pods was studied in a determinate snap-beancultivar (cv. Tenderette). Under moderate temperature (e.g.27/17°C) the onset of pod development was associated withcessation of flower bud production and with enhanced abscissionof flower buds. Raising night temperature from 17°C to 27°Cstrongly reduced pod production, mature pod size and seeds perpod, while an increase in day temperature from 22°C to 32°Chad smaller and less consistent effects. Pod production underhigh night temperature was not constrained by flower productionsince 27°C at night promoted branching and flower bud appearance.Under 32/27°C day/night temperature the large reductionin pod set was due to enhanced abscission of flower buds, flowersand young pods ( 3 cm). Flowers had the highest relative abscissionfollowed by young pods and flower buds. Therefore, the onsetof anthesis and of pod development were the plant stages mostsensitive to night temperature. Pods larger than 3 cm did notabscise but usually aborted and shrivelled under high nighttemperature. The effects of 32/27°C were not due to transientwater stresses and were observed even under continuous irrigationand mist-spraying. High temperature, flower production, pod set, seed set, abscission, snap bean, Phaseolus vulgaris L, Tenderette     

Analysis of the Control of Development in Oryzopsis miliacea by the Light Environment

The developmental responses of Oryzopsis miliacea plants tothe light environment were separated into those resulting fromthe level of incident solar radiation and those resulting fromthe photoperiod (comparing 16 h, which are inductive for flowering,with 8 h, which are not). The rate of leaf appearance and thetransition from the vegetative to the reporductive state, weredetermined by photoperiod and not by radiation level. In inductivephotoperiods, the ontogenetic timing of internode elongationwas unaffected by radiation level. Lowering the radiation levelprogressively delayed and reduced the activation of axillarybuds and crown roots, whereas photoperiod was without significanteffect. Accumulation of dry matter was progressively reducedas the radiation level was lowered, without affecting its distributionbetween the root and shoot systems. The mean dry-matter contentof a single shoot, as well as that of a single crown root, werealso unaffected by radiation level. The shorter photoperiodresulted in the diversion of a greater proportion of the drymatter to the root system, with the result that individual shootsaccumulated less, and individual roots accumulated more drymatter than in the longer photoperiod. Leaf blades in comparablenodal positions were consistently smaller and contained lessvasucular bundles in the longer photoperiod. These effects wereapparently due to inhibition of the trend for increasing cellproliferation in the surface plane by the long photoperiod,and its very small effect on the trend for diminution in celldimensions in blades on progressively higher nodes. The levelof solar radiation also affected blade surface dimensions, lowerlevels resulting in progressively larger surfaces, but the effectsof photoperiod and those of nodal position were equally modified.The longer photoperiod reduced the cross-sectional area of theinterbundle chlorenchyma strands, without affecting its shape,while reduction in radiation level caused an increase in itswidth and a compensating decrease in its thickness, thus changingthe shape of the cross-section without affecting its area.     

Control of the Germination Responses of Amaranthus retroflexus L. Seeds by their Parental Photothermal Environment

Germination responses of the seeds of Amaranthus retroflexusL. were affected by the photoperiod, temperature, and levelof solar radiation experienced by their parent plants. Seedsfrom parents grown continuously in short days (SD, 8 h) lostpost-harvest dormancy more rapidly and had a higher dark germination,as well as a greater responsiveness (at 30?C) to pretreatmentsat low temperature (5 or 10?C) and to short illuminations, thanseeds from parents grown continuously in long days (LD, 16 h).Dark germination and responsiveness of the seeds to promotivetreatments were both higher when their parents were transferredat flowering from LD to SD than when grown continuously in LD.These responses were lower when their parents were similarlytransferred from SD to LD than when grown continuously in SD.The promotive effects of parental post-flowering SD on darkgermination (at 30?C) were enhanced by reduction of parentaltemperature (from 27/22?C to 22/17?C), but the responsivenessof the seeds to low temperature pretreatment was reduced. Inflorescencesdeveloping in LD produced seed with higher germinability whenfloweringwas not induced (LD throughout) than when it was induced (eitherby SD till flowering, or by three SD cycles when 4–5 leavesappeared). Reduced levels of solar radiation had opposite effectsin the different parental photoperiods: dark germination andthe responsiveness to low temperature pretreatments were reducedin LD, but were increased in SD. Differences in the germination responses resulting from differencesin the parental environment could not be correlated with differencesin seed coat thickness or seed dry weight.