Quantitation of gibberellins and indoleacetic acid in Begonia leaves: Relationship with environment, regeneration and flowering

Indole-3-acetic acid (IAA) was purified by high performance liquid chromatography (HPLC) and identified by gas chromatography - mass spectrometry (GC-MS) in leaf extracts of Begonia × cheimantha Everett cv. Nova. The content of IAA and of gibberellins A4, A9, A19 and A20 (GAs) previously identified in this material, were quantified by GC-MS in leaves of Begonia plants grown under different temperature and daylength conditions, using deuterated compounds as internal standards. GA1, which was also identified, was present in too low quantities for reliable quantitation. Rapid and significant decreases (within 2–4 days) occurred in the content of both IAA and GAs when the plants were transferred from conditions which are non-inductive for adventitious bud formation and flowering (24°C/long day) to inductive conditions (24°C/short day, 15°C/long day or 15°C/short day). GA4 and GA9 were affected by photoperiod only, whereas IAA, GA19 and GA20 were affected by both photoperiod and temperature. The data suggest that biosynthesis of GA9 and GA4 are blocked in short days at a step located before GA9. Conversion of GA19 to GA20 seemed to be blocked by both short days and low temperature, while an additional block located before GA19 seemed to be imposed in 15°C/short day. The results confirm earlier results and support the hypothesis that photoperiod and temperature effects in Begonia are mediated by endogenous hormones.     

The Relationship between Flower Abortion and Endogenous Auxin Content of Rose Shoots

The amount of endogenous growth substances in stem, flowers and leaves of rose plants grown under different temperature and light conditions has been determined. It appeared to be two main growth promoting factors in the acidic fraction of the ether extract. One of them is assumed to be an auxin, probably indol-3yl-acetic acid (IAA); the other is not identified. The level of auxin was much higher in extracts from shoots grown at high temperature than in shoots grown at low temperature. Increasing light intensity also seemed to increase the auxin content of the shoots. Shoots which developed after a high cut back of the rose stem had a higher auxin content than shoots which developed after a low cut back. These findings are discussed in relation to the effect of temperature, light intensity and cut back practise on blind shoot formation in roses. The result of these investigations strongly indicate that abortion in roses is promoted by a low auxin level in the shoots.     

Effects of temperature and gibberellin on the activity of endogenous cytokinin-like substances in leaves of Begonia x cheimantha

Changes in activity of endogenous cytokinin-like substances were examined in intact plants and excised leaves of Begonia x chemantha Everett cv. Prinsesse Astrid (Christimas Begonia) by means of the tobacco callus bioassay. Cytokinin activity in the leaves of intact plants was higher in plants grown at 18°C than in those grown at 21° or 24°C. In excised leaves, an increase in cytokinin activity was observed during the first 4 days following leaf detachment. However, after the seventh day cylokinin activity decreased again. This decrease was more profound in leaves exposed to 24°C than in those exposed to 18°C.
Treatment of detached leaves with gibberellic acid (2.8 m M ) caused an increase in measurable cytokinin activity. This increase was more profound in the zones of activity which correspond with zeatin glucosides on paper and Sephadex LH-20 chromatography. Additional zones of activity appeared after Sephadex chromatography. These were of a more slow moving nature with elution volumes corresponding to N^b-(Δ²-isopentenyl)adenine and its derivaties. Water-treated control leaves had higher activity in the regions corresponding to zeatin and zeatin riboside.     

Indole auxins in spinach plants grown in long and short days

The endogenous auxin-like substances were analyzed in the shoot extracts of young spinach seedlings, exposed to photoperiodic induction. At least eight indole auxins were found. One of them was identified as tryptophan, the other one is most probably IAA. The plants grown in long days had a higher level of ether soluble auxins than the controls in short days. Separate extractions of plants after each of the eight inductive days showed that the auxin content was not constant, but subjected to irregular oscillations. However, parallel oscillations were also found in control plants grown in short days. Staminate plants were found to contain more endogenous auxins than the pistillate ones. It is concluded that the quantitative changes in auxins during the photoperiodic induction are probably not related to flowering, but to some other growth process, common to all plants in that phase of growth. The higher level of auxins in staminate plants may be the cause of their faster elongation before the onset of flowering.     

Effects of growth temperature and chilling duration on leaf phenology of <Emphasis Type="Italic">Fauria crista</Emphasis>-<Emphasis Type="Italic">galli</Emphasis> subsp. <Emphasis Type="Italic">japonica</Emphasis>, an alpine snowbed geophyte

I examined the effects of growth temperature and winter duration on the leaf phenology of Fauria crista-galli plants, which have an indeterminate growth habit. After a 220-day chilling treatment, the leaf expansion and green periods of plants maintained at 25/20°C were much longer than those of plants maintained at 15/10°C and of plants at the natural habitat obtained in a previous study. The results indicate that early growth cessation and early leaf senescence in the natural habitat are not only due to endogenous rhythm but determined to some extent by cool summer temperatures. When grown at 15/10°C, the green period of individual leaves and plants was much shorter after a long chilling treatment (220 days) than after a short chilling treatment (110 days). The plants sprouted during or immediately after the termination of chilling treatment, suggesting that the decrease in the green period results partly from an advance of endogenous developmental stages during the chilling treatment and that the timing of snowmelt potentially affects the time of leaf senescence in the natural habitat.     

Mobilization of sulphur in soybean cotyledons during germination

Soybean seeds ( Glycine max L. cv , Stephens) contain a large amount of sulphur (ca 40 μ mol seed⁻¹), mostly in the insoluble fraction in the cotyledons. During germination in nutrient solution lacking sulphur the amount of insoluble sulphur decreases to very low levels. This is accompanied by a transitory increase in the pool of soluble sulphur which then declines. All of the sulphur lost from the cotyledons is quantitatively recovered in the seedling. In the short term, the root and the stem are the most important sinks for sulphur from the cotyledons but as growth proceeds the shoot becomes the dominant sink for remobilized sulphur. Within the shoot most of the sulphur is recovered in leaves L1 and L2. The growth of L3 and, to a lesser extent, L2, was retarded due to sulphur insufficiency. The cotyledons of plants treated with 20 μ M sulphate also exhibited mobilization of sulphur from the insoluble fraction except that the maximum rate of loss of sulphur occurred somewhat later. Plants grown with sulphate exhibited a net gain of sulphur and did not exhibit sulphur insufficiency. In these plants, endogenous sulphur from the cotyledons was directed into L1–L3 and this sulphur remained within these leaves for the duration of the experiment. The delivery of exogenous sulphur (supplied as [³⁵S]sulphate via the roots) to the leaves increased with leaf number. In leaves L1–L3, the level of exogenous sulphur in any one leaf declined with time, indicating that this sulphur was remobilized and did not mix with the sulphur derived from the cotyledons. It was concluded that the cotyledons are an important source of sulphur to support early plant growth and development of soybean.     

Interaction of Growth Retardants and Temperature in Growth, Flowering, Regeneration, and Auxin Activity of Begonia × cheimantha Everett

Soil application of CCC reduced stem and leaf growth in Begonia plants. This effect was evident with all concentrations tested at 18°C, whereas at 21 and 24°C no growth–retarding effect was observed with 2 × 10^?2 M CCC, and with 5 × 10^?3 M growth was even stimulated. Flowering was promoted by CCC in long day and neur–critical temperature, particularly under low light intensity in the winter. The formation of adventitious buds in leaves of plants grown at 21 and 24°C was stimulated when the plants received 5 × 10^?2 and 2 × 10^?2 M CCC, while 8 7times; 10^?2 M was inhibitory. In plants grown at 18°C bud formation was inhibited by all CCC concentrations. Root formation in the the leaves was usually stimulated by high CCC concentrations, while root elongation was reduced. The level of ether–extractable. acidic auxin (presumably IAA) in the leaves was lowered by CCC treatment of the plants, hut this required higher CCC concentrations at higt than at low temperature. When applied to detached leaves CCC stimulated bud formation at concentrations ranging from 10^?4 to 10^?2 M in leaves planted at 18 and 21°C. At 24°C budding was inhibited by 10^?2 M CCC, the lower concentrations being stimulatory also at this temperature. Root formation and growth were not much affected by CCC treatment of the leaves, but increased with the temperature. Soil application of Phosfon (4 × 10^?4 M) had no effect on growth and flowering, nov did it affect the subsequent regeneration of buds and roots in the leaves. In detached leaves Phosfon stimulated bud formation with au optimum at 10^?6 M. Root formation was stimulated by Phosfon at all temperatures, the optimal concentration being 10^?5 M, whereas root length was conversely affected. Foliar application of B-995 to intact plants and treatment of detached leaves greatly inhibited the formation of buds and had little effect on root formation. B-99D reduced the growth and delayed flowering in the plants.     

Thermal acclimation of leaf and root respiration: an investigation comparing inherently fast- and slow-growing plant species

We investigated the extent to which leaf and root respiration (R) differ in their response to short‐ and long‐term changes in temperature in several contrasting plant species (herbs, grasses, shrubs and trees) that differ in inherent relative growth rate (RGR, increase in mass per unit starting mass and time). Two experiments were conducted using hydroponically grown plants. In the long‐term (LT) acclimation experiment, 16 species were grown at constant 18, 23 and 28 °C. In the short‐term (ST) acclimation experiment, 9 of those species were grown at 25/20 °C (day/night) and then shifted to a 15/10 °C for 7 days. Short‐term Q₁₀ values (proportional change in R per 10 °C) and the degree of acclimation to longer‐term changes in temperature were compared. The effect of growth temperature on root and leaf soluble sugar and nitrogen concentrations was examined. Light‐saturated photosynthesis (A_sat) was also measured in the LT acclimation experiment. Our results show that Q₁₀ values and the degree of acclimation are highly variable amongst species and that roots exhibit lower Q₁₀ values than leaves over the 15–25 °C measurement temperature range. Differences in RGR or concentrations of soluble sugars/nitrogen could not account for the inter‐specific differences in the Q₁₀ or degree of acclimation. There were no systematic differences in the ability of roots and leaves to acclimate when plants developed under contrasting temperatures (LT acclimation). However, acclimation was greater in both leaves and roots that developed at the growth temperature (LT acclimation) than in pre‐existing leaves and roots shifted from one temperature to another (ST acclimation). The balance between leaf R and A_sat was maintained in plants grown at different temperatures, regardless of their inherent relative growth rate. We conclude that there is tight coupling between the respiratory acclimation and the temperature under which leaves and roots developed and that acclimation plays an important role in determining the relationship between respiration and photosynthesis.     

Time course of photosynthetic temperature acclimation in Carex eleocharis Bailey

Abstract Photosynthetic temperature acclimation in Carex eleocharis has been demonstrated in a previous study in which warm grown (35/15°C) plants were shown to have photosynthetic temperature optima approximately 14°C higher than cool grown (20/15°C) plants (Monson, Littlejohn & Williams, 1983). The current study examined the time course of this acclimation by determining photo-synthetic temperature optima as a function of time, of cool grown plants moved to warm growing conditions. Leaves which had developed under cool conditions were capable of an upward adjustment of 6–8°C of their optimum photosynthetic temperature within a time span of 6–14 d. For greatest photosynthetic temperature acclimation it was necessary for leaves to form and develop entirely under warm conditions. These leaves exhibited a 14–15°C upward adjustment of their optimum temperature for photosynthesis within 20–31 d since moving plants from cool to warm growing conditions. Thus, the time course of this acclimation is of short enough duration to be significant during the growing season and presumably contributes toward the ability of this species to maintain active growth during the cool and warm portions of the growing season. It is also noted that the plant with its capacity to form new leaves, has a much wider acclimation capacity than any single leaf.     

The effect of air humidity on nutrient uptake of some greenhouse plants

Young plants of nine different greenhouse species were grown for 24 to 100 days at 55–60, 70–75, and 90–95% relative air humidity (RH) in growth rooms. They were given a complete nutrient solution twice a week. Transpiration rate decreased significantly by increasing RH from the lowest to the highest level inEuphorbia pulcherrima (60%), Begonia × hiemalis (54%), Saintpaulia ionantha (54%), Nephrolepis exaltata (48%), andLycopersicon esculentum (44%). The content of macro nutrient elements in the plant leaves decreased by increasing RH. This decrease was significant only for K and Ca in Lycopersicon and Kjeldahl-N in Nephrolepis. The content of the macro nutrient elements in the growth medium at the end of the experiment was lowest when the plants had been growing at high RH. The elements mainly affected were N and K. Report No. 342     

Pattern of growth regulating substances in the leaves of vernalized sugar-beet during flowering period

The changes in the levels of growth regulating substances using the wheat coleoptile straight growth test were determined in the leaves of vernalized (flowering) and non-vernalized (non-flowering) plants of sugar-beet, cv. Poly-AG-Poland at two stages; the end of vernalization treatment (210 days from planting) and full-flowering stage. IAA was detected only in the extracts of the leaves of non-vernalized plants after210 days from planting. No inhibitory activity was detected, except in the case of the concentrated extract of the leaves of non-vernalized plants. This growth promoting zone was found at R_f 0.5–0.8 in the leaves of flowering plants after cold treatment and at flowering time. This zone of growth promoting action was suggested to have a major role in the flowering of sugar-beet.     

In vitro Organogenesis in Explants from Different Cultivars of Begonia X hiemalis

Petiole explants from 17 cultivars of Begonia X hiemalis were grown on a basal agar medium with different combinations of NAA and BA as well as on media lacking microelements or vitamins. The stock plants were kept either under short days (7–8 h of light perday) at 15°C or under long days (15–16 h of light) at 18–21°C. The day length during the in vitro culture was 20 h of light and the temperature 21°C. Explants from short-day treated stock plants did not show any differentiation. In explants from long-day treated stock plants, the percentage of explants with shoot, root and with both shoot and root initiation were recorded after 55 days. Explants forming both shoots and roots were transferred to soil, and plantlet formation was observed after another 55 days. The percentage of explants with organ and plantlet formation differed between cultivars. With increasing NAA and decreasing BA concentrations, the percentage of explants forming only roots increased, whereas the percentage of explants with only shoots decreased. Plantlet formation was most frequent in explants from NAA: BA ratios of 2: 1 and 10: 1, and a variation was found between different cultivars. When the vitamin fraction was not added to the medium, this did not influence formation of shoots, roots and plantlets. When the microelements were omitted. shoots, roots and callus were formed, but no plantlets.     

Photoperiodic control of growth, development and phytohormone balance in Solanum tuberosum

Some lines of Solanum tuberosum ssp. andigena are strictly photoperiodic, forming tubers only in short days and flowers only in long days. We used this advantageous phenomenon to study phytohormone involvement in the development of the plants, mainly that of tuber formation. Plants grown for 2 months under short days (SD) of 14 h darkness, night break (1 h white light in the middle of the 14‐h dark period) and continuous light (LD) were compared. Short day‐grown plants formed tubers, while plants in LD flowered. Night break prevented tuber formation, but caused flowering, although it was weaker than in LD. Plants grown under night break displayed many growth characteristics intermediate between SD and LD. Under LD and night break regimes ABA levels in all organs were about one‐fourth of those under SD. An opposite trend was found for gibberellin content: it was very low in SD‐grown plants and 4‐10 times higher under both other conditions with the exception of roots and stolons in night break. Thus, the ratio of ABA/GA, known to be important for tuber formation, was high in SD and low in night break and LD. The level of free indoleacetic acid (IAA) was high in LD‐ and night break‐grown plants and it was much lower in SD‐grown plants, including tubers. Cytokinin (CK) levels were also high in LD‐ and night break‐grown plants. In SD, leaves had slightly decreased and stems and roots + stolons had more pronouncedly decreased cytokinin levels. The CK/IAA ratio was thus higher in SD in stems and roots + stolons; it was also high in tubers and no difference was found in leaves. These results indicate that the effect of photoperiod on tuber formation and development may be mediated by photoperiod‐induced changes in hormone levels.     

Effects of theobroxide, a natural product, on the level of endogenous jasmonoids

The natural potato microtuber inducing substance, theobroxide, strongly induces the formation of tuber of potato (Solanum tuberosum L.) and flower bud of morning glory (Pharbitis nil) plants under non-inducing conditions (long days) (Yoshihara et al., 2000). In the present study, theobroxide was evaluated for its effect on the level of endogenous jasmonoids in different tissues of such two plants. An in vitro bioassay using cultures of single-node segments of potato stems was performed with the supplement of theobroxide in the medium. The endogenous jasmonic acid (JA) and its analogue tuberonic acid (TA, 12-hydroxyjasmonic acid) in segments and microtubers were quantitatively analyzed. The increase in the endogenous JA level caused by theobroxide was observed in both segments and microtubers. Endogenous TA was only detected in segments, and the content increased with the concentration of theobroxide. As for morning glory, the whole plant was sprayed with theobroxide for 1 approximately 5 weeks under different photoperiods and endogenous JA in the leaves was quantitatively analyzed. Theobroxide spraying increased the level of endogenous JA in the leaves of the plants grown under both long and short days.     

Selenium Modifies the Effect of Short-Term Chilling Stress on Cucumber Plants

The objective of this study was to investigate the effect of selenium (Se) supply (0, control; 2.5, 5, 10, or 20 μM) on cucumber (Cucumis sativus L.) cv. Polan F1 plants grown under short-term low temperature stress. About 14–16 day-old seedlings, grown at an optimal temperature (25/20°C; day/night), were exposed to short-term chilling stress with a day/night temperature of 10°C/5°C for 24 h, for a further 24 h at 20°C/15°C, and then transferred to 25/20°C (re-warming) for 7 days. Se did not affect the fresh weight (FW) of plants at a concentration of 2.5–10 μM, but in the presence of 20 μM Se, the biomass of shoots significantly decreased. The contents of chlorophylls and carotenoids witnessed no significant change after Se supplementation. Compared with the control, the Se-treated plants showed an increase of proline content in leaves, once after chilling and again after 7 days of re-warming. However, proline levels were much higher immediately after chilling than after re-warming. The malondialdehyde (MDA) content in the root of plants treated with 2.5–10 μM Se decreased directly after stress. This was in comparison with the plants grown without Se, whereas it increased in roots and leaves of plants exposed to 20 μM Se. Seven days later, the MDA level in the root of plants grown in the presence of Se was still lower than those of plants not treated with Se and generally witnessed no significant change in leaves. Although Se at concentrations of 2.5–10 μM modified the physiological response of cucumber to short-term chilling stress, causing an increase in proline content in leaves and diminishing lipid peroxidation in roots, the resistance of plants to low temperature was not clearly enhanced, as concluded on the basis of FW and photosynthetic pigments accumulation.     

Jasmonic acid affects plant morphology and calcium-dependent protein kinase expression and activity in Solanum tuberosum

The effect of jasmonic acid (JA) on plant growth and on calcium-dependent protein kinase (CDPK) activity and expression was studied in non-photoperiodic potato plants, Solanum tuberosum L. var. Spunta, grown in vitro. Stem cuttings were grown for 45 days (long treatment, LT) in MS medium with increasing concentrations of JA. For short treatments (ST) adult plants grown in MS were transferred for 1, 4 and 20 h to JA containing media. During the LT, low concentrations of JA promoted cell expansion and shoot elongation while higher concentrations caused growth inhibition. Under these conditions, treated plants showed root shortening and tuber formation was not induced. Morphological and histochemical studies using light microscopy and TEM analysis of leaves from treated plants revealed that JA also affected subcellular organelles of mesophyll cells. Peroxisomes increased in size and number, and an autophagic process was triggered in response to high concentrations of the hormone. CDPK activity, determined in crude extracts of treated plants (LT), was inhibited (up to 80%). Plant growth and CDPK inhibition were reverted upon transfer of the plants to hormone-free medium. Soluble CDPK activity decreased in response to JA short treatment. Concomitantly, a decline in the steady state levels of StCDPK2 mRNA, a potato CDPK isoform that is expressed in leaves, was observed. These data suggest that the phytohormone down-regulated the expression and activity of the kinase.     

Efect of decapitation on the level of endogenous stimulators and inhibitors and some morphogenetic phenomena in peach trees

In experiments from 1966–1968 a comparison was performed concerning the level of endogenous stimulators and inhibitors in leaves and shoots of peaches decapitated in three different times and in controls. For the determination of these substances a biological test was employed after separation of the acid fraction of ethyl ether extracts by means of paper chromatography. Mathematical addition of total stimulations and inhibitions gave a new value, called “growth disposition” by the authors. Its graphical demonstration gives a simple curve which documents the growth rhythm of control plants as well as the response of plants to the time-regulated decapitation. In the case of shoots this response has always been positive,i.e. at all periods of sampling for analyses the growth disposition with decapitated plants was higher in comparison with controls.     

Thermosensitive genetic dwarfs of apple

The role of environment on the dwarfing (short internode) phenomenon of apple (Malus domestisca Borkh.) was investi gated and defined in controlled environmental chambers. Orchard-grown very dwarf, dwarf and semi-dwarf trees obtained by natural sibcrossing of spur-type cv. Golden Delicious and cv. Delicious, as well as standard cv. Golden Delicious, were propagated via in vitro techniques. Growth was rapid and none of the 4 types exhibited dwarf-like characteristics when grown at constant 27°C with 12, 14 or 16 h daylengths. Standard and very dwarf plants grew at nearly the same rate at constant 30°C, whereas growth nearly ceased on both types at constant 35°C after 7 days. Dwarf and very dwarf plants responded differently from standard and semi-dwarf plants when grown under alternating (ramped) night/day temperatures (15 or 20°C night ramped up to a daytime maximum over 8 h of 23, 28, 33 or 38°C, held for 2 h and then ramped down over 5 h to the night temperature). As the night/maximum day temperature differentia) increased from 0 to 23° under the ramping environments, growth of dwarf plants decreased markedly as compared to standard plants. When the same night/maximum day temperature differential occurred, the effect on decreasing shoot length was greater at the higher (20°C) night temperature. Increasing maximum day temperatures under the ramped environment also reduced leaf area plant^?1 but did not markedly affect leaf number, resulting in short internodes. When a period of constant temperature was followed by ramped temperatures or vice versa, the sequence of constant vs ramped environments made little difference in the final growth of the 4 plant types. The data point to high temperature as the major factor for causing dwarfing of the sensitive plant types. Increasing the differential between night and maximum day temperature resulted in short internode. dwarf plants with small leaves similar to orchard-grown dwarf trees.     

Acid phosphatase activity in maize leaves as related to their evolution and phosphorus deficiency

The effect of phosphorus deficiency on the activity of acid phosphatase of the first, second and third leaves of maize plants was followed. The supernatant obtained by centrifuging the homogenate of plant tissue at 1500 ×g was further centrifuged at 18 000 ×g, the sediment marked as fraction II and the supernatant as fraction III. Acid phosphatase activity of fraction II of the first to third leaves was for the whole period of culture higher in plants grown in the nutrient solution without phosphate. In fraction III this relation was established in the first leaf, after 3 days of culture in the second leaf and after 5 days in the third leaf. In all leaves higher enzyme activity was unambiguously determined in fraction III when compared with fraction II. Higher acid phosphatase activity was established in those leaves which were younger in their development, particularly in the first days of culture. With the ageing of leaves the enzyme activity decreased.     

The effect of NO3- and NH4 + ions on enzymes involved in nitrogen assimilation inPisum sativum L

Nitrate reductase level in leaves of pea plants is higher than in roots despite of the lower content of endogenous nitrate. Addition of ammonium ions to nutrient solution containing nitrate decreases nitrate reductase level in leaves estimatedin vivo while its level estimatedin vitro is increased. Glutamine synthetase (GS) level in roots decreases during short (24 and 48 h) and long (14 d) term cultivation of seedlings in solutions containing ammonium ions. This decrease occurs in leaves only after the long term influence of ammonium ions. Level of this enzyme is higher in plants grown in the presence of nitrogen (ammonium and nitrate) as compared to those grown without the nitrogen. Level of glutamate dehydrogenase in roots is increased after both short and long term cultivation of plants in the presence of ammonium ions.