Photoperiodic control of endogenous gibberellins in seedlings of Salix pentandra

In the temperate-zone woody species Salix pentandra elongation growth is regulated by the photoperiod. Long days sustain active growth, whereas short days induce cessation of apical growth, which is a prerequisite for winter hardening. It is shown that this is correlated to quantitative changes in levels of endogenous GA₁₉ GA₂₀, and GA₁. Within two short days the amount of the active GA₁ and its immediate precursor GA₂₀, decreased markedly in young leaves us well as in stem tissue. Also, the amount of GA¹⁹, declined, but the decrease was delayed relative to that of GA₁ and GA₂₀. The ability of S. pentandra seedlings to respond to exogenous GA₁₉, decreased with increasing numbers of short days. Observations that support the hypothesis that the level of GA₁ in S. pentandra is regulated by the photoperiod in a quantitative mode with conversion of GA₁₉, to GA₂₀, being one target for control.
Different distribution of GAs in various plant parts was observed. The level of GA was higher in young leaves than in other plant parts, and the amount of GA₁₉ was 5–10 times higher in stem tissue than in leaves and roots. The ratios of GA₈ to GA¹ and GA₂₀, were higher in roots as compared with other parts, as rods contained very low levels of GA₁ and GA₂₀, but amounts of GA₂₀ comparable with other parts.     

Flower bud differentiation in Salix pentandra as affected by photoperiod, temperature and growth regulators

Flower bud initiation in seedlings and vegetatively propagated plants of Salix pentandra from different locations has been studied under controlled conditions. In mature plants flower bud formation was induced by 2-chloroethyltrimethylammoniumchloride (CCC) and by short day treatment. The effect of CCC was antagonized by GA₃. The critical photoperiod for flower bud formation was about 18 h for a southern clone (from 49°48'N), but cuttings of a northern ecotype (from 69°39'N) formed flower buds even at 24 h photoperiod. Generally, flower bud formation occurred simultaneously with apical growth cessation. However, apical growth cessation was not a prerequisite for floral initiation and flower buds were also found in elongating plants. Seedlings up to 60 days old did not form flower buds in growth chamber studies. The length of the juvenile phase has not been studied in detail, but cuttings taken from seedlings approximately 20 cm high and 60 days old were able to develop flower buds when treated with CCC. A gradual transition from the juvenile to the mature phase was obtained by repeated pruning of seedlings grown at 18°C and 24 h photoperiod.     

Growth-promoting activity of gibberellins on shoot elongation in Salix pentandra is reduced by 16,17-dihydro derivatisation

The metabolism of GA₁₀ is thought to be under photoperiodic control in the woody plant Salix pentandra . However, in a recent study using 16,17-[³H₂]GA₁₉ as a mimic of Ga₁₀, no effect of photoperiod was found on its metabolism to 16,17-dihydro-GA₂₀ and 16,17-dihydro-GA₁. To investigate if this was due to differential action of exogenous 16,17-dihydro-GAs and GAs, the effects of the 16,17-dihydro-derivatives of the gibberellins GA₁₉, GA₁, and GA₁ as compared with their parent GAs, on shoot elongation in seedlings of S. pentandra were studied. 16,17-Dihydro-GA₁₉, and -GA₂₀ were both almost inactive, while 16,17-dihydro-GA₁ induced some shoot elongation in seedlings treated with ancymidol as well as under short days. GA₁₉, GA₂₀ and GA₁ were all able to counteract the inhibitory effect of ancymidol under continuous light, while inhibition induced by a 12-h photoperiod was antagonised only by GA₂₀ and GA₁. Thus, the growth-stimulating activity of the tested GAs is significantly reduced by 16,17-dihydro derivatisation, but the derivatives do not inhibit stem elongation in S, pentandra , as has been found in monocotyledons.     

Gibberellins in Leaves of Alstroemeria hybrida: Identification and Quantification in Relation to Leaf Age

In alstroemeria (Alstroemeria hybrida), leaf senescence is retarded effectively by the application of gibberellins (GAs). To study the role of endogenous GAs in leaf senescence, the GA content was analyzed by combined gas chromatography and mass spectrometry. Five 13-hydroxy GAs (GA₁₉, GA₂₀, GA₁, GA₈, and GA₂₉) and three non-13-hydroxy GAs (GA₉ and GA₄) were identified in leaf extracts by comparing Kováts retention indices (KRIs) and full scan mass sprectra with those of reference GAs. In addition, GA₁₅, GA₄₄, GA₂₄, and GA₃₄ were tentatively identified by comparing selected ion monitoring results and KRIs with those of reference GAs. A number of GAs were detected in conjugated form as well. Concentrations of GAs in alstroemeria changed with the development of leaves. The proportion of biologically active GA₁ and GA₄ decreased with progressive senescence and the fraction of conjugated GAs increased. Received May 26, 1997; accepted August 12, 1997     

Lack of effect of photoperiod on metabolism of exogenous GA19 and GA1 in Salix pentandra seedlings

The effect of photoperiod on metabolism of 16,17-[³H₂]GA₁₉, and 1.2-[³H₂]GA₁ applied to intact seedlings of Salix pentandra, was investigated. No difference was found in conversion of 16,17-[³H₂]GA₁₉ to 16,17-[³H₂]GA₂₀, and 16,17-[³H₂]GA₁, or in metabolism of 1,2-[³H₂]GA₁ to [³H]GA₈ between plants grown in continuous light and plants exposed for 14 days to a 12-h photoperiod. Also, leaf discs from plants grown in long or short days, converted 16,17-[³H₂]GA₁₉ both in light and darkness. These data on metabolism of 16,17-[³H₂]GA₁₉, contrast with previous results, which have indicated a photoperiodic control of the metabolism of GA₁₉ to GA₂₀ in S. pentandra. Presence of these applied labelled GAs and their metabolites in different parts of seedlings was recorded, after application to intact seedlings as well as to isolated plant parts. When 16,17-[³H₂]GA₁₉ was applied through the roots of intact plants, the relative amounts of 16,17-[³H₂]GA₁ present in leaves and shoot apices were higher than in roots and stems. In corresponding experiments with 1,2-[³H₂]GA₁, relatively higher amounts of [³H₂]GA₈ were found in roots and stems than in leaves and shoot apices. Twenty-four hours after application of 16,17-[³H₂]GA₁₉ to isolated plant parts, 16,17-[³H₂]GA₂₀ and 16,17-[³H₂]GA₁ were found in leaves and roots, but not in internodes. Incubation of isolated plant parts with 1,2-[³H₂]GA₁ for 24 h resulted in presence of [³H]GA₈ in all parts. The results mentioned above were obtained by monitoring metabolites by HPLC with on-line radio counting. The conversions of 17-[²H₂]GA₁₉ to 17-[²H₂]GA₂₀ and 17-[²H₂]GA₁ in shoot apices and whole seedlings, and of 17-[²H₂]GA₈ in whole seedlings, were confirmed by GC-MS.     

Thermo- and Photoperiodicity and Involvement of Gibberellins during Day and Night Cycle on Elongation Growth of Begonia x hiemalis Fotsch

The effects of thermo- and photoperiodicity on elongation growth and on endogenous level of gibberellins (GAs) in Begonia x hiemalis during various phases of the day-night cycle have been studied. Plant tissue was harvested during the day and night cycle after temperature and photoperiodic treatments and analyzed for endogenous GAs using combined gas chromatography and mass spectrometry. Elongation growth increased when the difference between day and night temperature (DIF = DT − NT) increased from a negative value (−9.0 and −4.5°C) to zero and with increasing photoperiod from 8 to 16 h. When applied to the youngest apical leaf, gibberellins A₁, A₄, and A₉ increased the elongation of internodes and petioles. GA₄ had a stronger effect on elongation growth than GA₁ and GA₉. In relative values, the effect of these GAs decreased when DIF increased from −9 to 0°C. The time of applying the GAs during a day and night cycle had no effect on the growth responses. In general, endogenous levels of GA₁₉ and GA₂₀ were higher under negative DIF compared with zero DIF. The level of endogenous GA₁ in short day (SD)-grown plants was higher under zero DIF than under negative DIF, but this relationship did not appear in long day (LD)-grown plants. The main effects of photoperiod seem to be a higher level of GA₁₉ and GA₁ at SD compared with LD, whereas GA₂₀ and GA₉ show the opposite response to photoperiod. No significant differences in endogenous level of GA₁, GA₉, GA₁₉, and GA₂₀ were found for various time points during the diurnal day and night cycle. Endogenous GA₂₀ was higher in petiole and leaf compared with stem, whereas there were no differences of GA₁, GA₉, and GA₁₉ between plant parts. No clear relationship was found between elongation of internodes and petioles and levels of endogenous GAs. Received December 26 1996; accepted July 1, 1997     

A localised decrease of GA1 in shoot tips of Salix pentandra seedings precedes cessation of shoot elongation under short photoperiod

By application of a recently developed method allowing analysis of gibberellins (GAs) in mg amounts of tissue, the effect of photoperiod on levels of GAs in shoot tips of individual seedlings of the woody species Salix pentandra was studied. In elongating long day-grown seedlings, maximum levels of GA₁ were found 5–20 mm below the apex, approximately twice the levels in other segments. After exposure of plants to 5 or 15 short days, the levels of GA₁ were about 50% lower within this specific region of the stem, as compared with seedlings grown under long days. Short day-induced cessation of shoot elongation also correlated with overall declines in the levels of GA₅₃, GA₁₉, GA₂₀ and GA₈, Within each photoperiodic treatment the levels of these GAs were generally relatively similar throughout the upper 35 mm of stems. No differences in internode lengths or in lengths of pith or epidermal cells were found in plants grown under long days compared with those exposed to 5 short days. In both cases, cells in mitosis were observed in the subapical stem tissues of shoot tips. After 15 short days, stem elongation was completed, and dividing cells were generally not found in the subapical part of the stem. However, short day exposure did not prevent elongation of internodes and cells differentiated before the treatment was started. Thus, the localised decrease in level of GA₁ in shoot tips under short days precedes the morphological and anatomical changes connected with the short day-induced cessation of elongation growth. This supports the hypothesised role for GA₁ in photoperiodic control of shoot elongation in S. pentandra .     

Comparison of endogenous gibberellins in roots and shoots of elongating Salix pentandra seedlings

Gibberellins GA₁, GA₈. GA₁₉. GA₂₉. GA₂₀ and GA₅₆ (2-epi-GA₈). were identified by combined gas chromatography-mass spectrometry in root extracts of elongating Salix pentandra L. seedlings. The presence of GA₈ was also demonstrated for the first time in S. pentandra shoots. The levels of GA₁, GA₈, GA₁₉, GA₂₀ in shoot tissue and in roots were estimated by selected ion monitoring. While the amounts of GA₈ and GA₁₉ were similar in both plant parts. the levels of the biologically active GA₁ and its immediate precursor GA₂₀. were found to be much lower in roots than in shoots.     

Gibberellins and photoperiodic control of shoot elongation in Salix

Effects of exogenous gibberellins GA₅₃, GA₄₄, GA₁₉, GA₂₀ and GA₁ on photoperiodically controlled shoot elongation in seedlings of Salix pentandra L. were studied. Gibberellins GA₂₀ and GA₁ induced shoot elongation under short days (SD) and could substitute for a transfer to long day (LD), while gibberellins A₅₃, A₄₄ and A₁₉ were inactive. In seedlings exposed to a prolonged SD-treatment (30 days) there was a significant positive interaction between a transfer to LD and a treatment with GA₂₀ and GA₁ on shoot elongation. In addition, GA₁₉ enhanced the growth promotive effect of LD in these seedlings. The results are compatible with the suggestion that conversion of GA₁₉ to GA₂₀ is blocked under SD. This effect is supposed to be an early process leading to the cessation of shoot elongation under SD. Responsiveness of the seedlings to LD and to a GA-treatment gradually decreased with an increasing length of exposure to SD.     

Effects of Ring D-Modified Gibberellins on Gibberellin Levels and Development in Selected Sorghum bicolor Maturity Genotypes

Plants of early flowering mutant and wild type genotypes of Sorghum bicolor were treated with ring D-modified gibberellins (GAs), and the effects on endogenous GA levels were determined. The growth and timing of floral initiation in 58M plants grown under 18-h days (which significantly delays floral initiation in this short day plant) following treatment with these compounds, relative to GA₃ and GA₅ treatments, were also investigated. Application of the endo-isomer of C16,17-dihydro-GA₅ (endo-DiHGA₅), the exo-isomer of C16,17-dihydro-GA₅ (exo-DiHGA₅), and C16α,17-dichloromethanodihydro-GA₅ (DMDGA₅) altered GA levels in both genotypes. Each ring D-modified GA significantly inhibited shoot growth while significantly decreasing levels of GA₁ and increasing levels of its immediate precursor, GA₂₀. Gibberellin A₈ levels also decreased. Tillering was not affected by any treatment. For the early flowering genotype 58M, grown under noninductive long days, both dihydro-GA₅ isomers promoted floral initiation while shoot growth was strongly inhibited, and floral development was strongly advanced beyond floral stage 4. Gibberellin A₃ and GA₅, applied under the same conditions, promoted shoot growth slightly and gave ``floral-like' apical meristems that did not develop past floral stage 1. These results suggest that the reduced shoot growth of sorghum, which follows application of those ring D-modified GAs, is due to their inhibiting the 3β hydroxylation of GA₂₀ to GA₁, thereby reducing the GA₁ content. That floral initiation was hastened and floral development promoted in genotype 58M by application of both isomers of DiHGA₅ are in contrast to the effects of other GA biosynthesis inhibitors, which act earlier in the GA biosynthesis pathway, but are consistent with results seen for long day grasses. This suggests that endo-DiHGA₅ and exo-DiHGA₅ may be acting directly in promoting floral initiation and subsequent floral apex development of this short day plant under long day conditions. Received October 3, 1996; accepted January 22, 1997     

Thermomorphogenic and Photomorphogenic Control of Stem Elongation in Fuchsia Is Not Mediated by Changes in Responsiveness to Gibberellins

Stem elongation in Fuchsia × hybrida was influenced by cultivation at different day and night temperatures or in different light qualities. Internode elongation of plants grown at a day (25°C) to night (15°C) temperature difference (DIF+10) in white light was almost twofold that of plants grown at the opposite temperature regime (DIF−10). Orange light resulted in a threefold stimulation of internode elongation compared with white light DIF−10. Surprisingly, internode elongation in orange light was similar for plants grown at DIF−10 and DIF+10. Flower development was accelerated at DIF−10 compared with DIF+10 in both white and orange light. To examine whether the effects of DIF and light quality on shoot elongation were related to changes in gibberellin metabolism or plant sensitivity to gibberellins (GAs), the stem elongation responses of paclobutrazol-treated plants to applied gibberellins were determined. In the absence of applied gibberellins paclobutrazol (>0.32 μmol plant⁻¹) strongly retarded shoot elongation. This inhibition was nullified by the application of about 10–32 nmol of GA₁, GA₄, GA₉, GA₁₅, GA₁₉, GA₂₀, GA₂₄, or GA₄₄. The results are discussed in relation to possible effects of DIF and light quality on endogenous gibberellin levels and gibberellin sensitivity of fuchsia and their effects on stem elongation. Received October 4, 1997; accepted December 17, 1997     

Conditioning of Fasciation by Gibberellin and Genotype in Cotton (Gossypium hirsutum L.)

The round-leafed mutant cotton line L-501 developed fasciation of the upper stem when field grown in Central Asia. Fasciation co-segregated with the mutant gene for round leaves In. ^l Fasciation developed at the flowering stage, but removal of floral buds did not prevent fasciation. Fasciation in L-501 could be inhibited by the gibberellin (GA) biosynthesis inhibitor chlorocholine chloride or by fusicoccin. GA₃ application in the field induced fasciation in the mutant's parental line L-463, which has five-lobed leaves and does not normally develop fasciation. Fasciation did not develop in either line, even after GA₃ treatment, in UK glasshouse conditions. Received June 17, 1998; accepted January 25, 1999     

The Response to Gibberellin in Pisum sativum Grown under Alternating Day and Night Temperature

The application of gibberellins (GA) reduces the difference in stem elongation observed under a low day (DT) and high night temperature (NT) combination (negative DIF) compared with the opposite regime, a high DT/low NT (positive DIF). The aim of this work was to investigate possible thermoperiodic effects on GA metabolism and tissue sensitivity to GA by comparing the response to exogenously applied GA (in particular, GA₁ and GA₃) in pea plants (Pisum sativum cv. Torsdag) grown under contrasting DIF. Control plants not treated with growth inhibitors or additional GA were 38% shorter under negative (DT/NT 13/21°C) than positive DIF (DT/NT 21/13°C) because of shorter internodes. Additional GA₁ or GA₃ decreased the difference between positive and negative DIF. In pea plants dwarfed with paclobutrazol, which inhibits GA biosynthesis at an early step, the response to GA₁ was reduced more strongly by negative compared with positive DIF than the response to GA₃. The induced stem elongation by GA₁₉ and GA₂₀ did not deviate significantly from the response to GA₁. Plants treated with prohexadione-calcium, an inhibitor of both the production and the inactivation of GA₁, grew equally tall under the two temperature regimes in response to both GA₁ and GA₃. We hypothesize that the reduced response to GA₁ compared with GA₃ in paclobutrazol-treated plants grown under negative DIF is caused by a higher rate of 2β-hydroxylation of GA₁ into GA₈ under negative than positive DIF. This contributes to lower levels of GA₁ and consequently shorter stems and internodes in pea plants grown under negative than positive DIF. Differences in tissue sensitivity to GA alone cannot account for this specific thermoperiodic effect on stem elongation. Received May 28, 1998; accepted May 29, 1998     

Stimulation of shoot elongation in Salix pentandra by gibberellin A9; activity appears to be dependent upon hydroxylation to GAl via GA20

Cessation of shoot elongation in seedlings of Salix pentandra L. is induced by short photoperiod. Gibbereliin A₉ (GA₉) applied either to the apical bud or injected into a mature leaf, induced shoot elongation under a short photoperiod of 12 h, and GA₉ could completely substitute for a transfer to a long photoperiod. When [³H]GA₉ or [²H₂]GA₉ was injected into a leaf, no [³H]GA₉ was detected in the elongating apex and only traces of [³H]GA₉ were found in the shoot above the treated leaf. By the use of gas chromatography-mass spectrometry (GC-MS), [²H₂]GA₂₀ was identified as the main metabolite of [²H₂]GA₉ in both the shoot and the treated leaf. In addition, [²H₂]GA₁ and [²H₂]GA₂₉ were also identified as metabolites of [²H₂]GA₉. These results are consistent with the hypothesis that exogenous GA, promotes shoot elongation in Salix through its metabolism to GA₂₀ and GA,.     

Effect of Gibberellin on Growth, Protein Secretion, and Starch Accumulation in Maize Endosperm Suspension Cells

The physiologic effect of gibberellins (GA) in seed development is poorly understood. We examined the effect of gibberellic acid (GA₃) on growth, protein secretion, and starch accumulation in cultured maize (Zea mays L.) endosperm suspension cells. GA₃ (5 and 30 μm) increased the fresh weight, dry weight, and protein content of the cultured cells, but the effect of GA₃ at 50 μm was not significantly different. However, the protein content in the culture medium was increased by these three concentrations of GA₃. The effect of GA₃ on the amount of cellular structural polysaccharides was not significant, but GA₃ had a dramatic effect on the starch content. At 5 μm, GA₃ caused an increase in the starch content, but at 50 μm the starch accumulation was reduced. Chlorocholine chloride (CCC), an inhibitor of GA biosynthesis, significantly increased the starch content and decreased the structural polysaccharide content of the cultured cells. The effects of CCC at 500 μm on the starch and polysaccharide content were partially reversed by 5 μm GA₃ applied exogenously. Based on these results we suggest that GA does not favor starch accumulation in the cell cultures and that the addition of lower concentrations of GA₃ in the medium may provide an improved balance among the endogenous GA in the cultured cells. Received October 31, 1995; accepted March 25, 1997     

Involvement of Abscisic Acid and Indole-3-acetic Acid in the Flowering of Pharbitis nil

The involvement of abscisic acid (ABA) and indole-3-acetic acid (IAA) in the regulation of flowering of Pharbitis nil was investigated through exogenous applications and analyses of endogenous levels. Both hormones inhibited the flowering of P. nil when they were applied before or after a single 15-h dark treatment. The inhibitory effect of ABA and IAA was significant when they were applied before the dark treatment, and the application to plumules was more effective than that to cotyledons. In all applications, the inhibitory effect of IAA was stronger than that of ABA. Endogenous levels of ABA and IAA in the plumules were compared between flower-inductive (15-h dark treatment) and noninductive (continuous light) light conditions. There was no significant difference in the ABA level between light and dark conditions, whereas the level of IAA was decreased by the dark treatment. These results suggest that biosynthesis and/or catabolism of IAA is affected by the light treatment and therefore may be involved in the regulation of early flowering processes in the apex. The inhibitory effects of ABA and IAA were reversed by an application of gibberellin A₃, indicating that gibberellin A₃ counteracts the flowering processes affected by ABA and IAA. Application of aminoethoxyvinylglycine restored the flowering response inhibited by IAA, which suggests the possibility that the inhibitory effect of IAA is the result of enhanced ethylene biosynthesis. Received November 22, 1996; accepted February 17, 1997     

Growth Responses and Allocation of Assimilates of Rice Seedlings by Paclobutrazol and Gibberellin Treatment

Paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)methyl-4,4-dimethyl-2-(1h-1,2,4-trizol-1-yl)penten-3-ol] effectively decreased vegetative growth of rice (Oryza sativa L.) seedlings and increased the chlorophyll content. The number of veins in a leaf, the calculated number of stomata per leaf, and the length of guard cells were not altered by the paclobutrazol treatment, suggesting an effect on cell elongation. The allocation pattern of carbohydrates was changed by either gibberellin (GA) or paclobutrazol treatment. GA₃ induced more shoot growth and less accumulation of starch than the control and paclobutrazol-treated seedlings. Photosynthetic ability was not affected by either paclobutrazol or GA₃ treatment. Paclobutrazol-treated plants allocated a smaller amount of photosynthates for vegetative shoot growth and stored more as starch in the crowns than the control and GA₃-treated plants. The same starch degrading activity in the crown tissue of paclobutrazol-treated seedlings as in control plants suggests that the accumulated starch is utilized in a normal activity for growth including leaf emergence, tiller formation, and root production, resulting in improved seedling quality. Received May 30, 1996; accepted December 10, 1996     

The pro Gene Causes an Enhanced Cell Expansion Response to Fusicoccin in Tomato

The response to fusicoccin (FC) of the elongated tomato mutant procera was tested. Hypocotyl sections from etiolated procera seedlings responded to a range of FC concentrations similar to that of normal sections, but at a given FC concentration the mutant sections exhibited about 40% greater elongation than normal. The initial rates of elongation in FC were similar for normal and procera sections, but elongation continued at a high rate for a longer period in the mutant. Measurements of outer cortical cells demonstrated that the enhanced elongation of the procera hypocotyl sections was due to enhanced cell expansion. Received July 16, 1996; accepted January 17, 1997     

Effects of Chemical Growth Retardants on Growth and Development of Sweetpotato (Ipomoea batatas (L.) Lam.) in Vitro

Plant growth retardants were evaluated for their ability to reduce the growth rate of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro. Nodal sections of cv. Jewel were cultured for 30 days on medium containing NDA, ancymidol, phosfon, TIBA, difenzoquat, chlormequat, ACC, mepiquat chloride, or daminozide at 0, 10⁻⁴, 10⁻⁵, 10⁻⁶, 10⁻⁷, or 10⁻⁸ m. Difenzoquat, NDA, phosfon, and TIBA, at 10⁻⁴ m, were lethal to axillary bud explants. A low concentration (10⁻⁸ m) of chlorflurenol or NDA stimulated shoot elongation. The effective concentration range for most growth retardants was 10⁻⁵ to 10⁻⁶ m. Small (2- to 4-mm diameter) storage root-like swellings were observed on roots in cultures containing TIBA or ancymidol. The growth-inhibiting effects of ancymidol and NDA were transitory and did not persist through a 180-day culture period. Shoots cultured on medium containing 10⁻⁵ m phosfon, TIBA, or difenzoquat were significantly shorter than control plants after a 180-day culture period. Culture on medium containing TIBA, NDA, ancymidol, or ACC resulted in abnormal leaf and stem development. Plants derived from nodal explants cultured on medium containing either phosfon or chlormequat were near normal in appearance but with some plants exhibiting interveinal chlorosis and reduced root system development. Received May 9, 1997; accepted August 14, 1997     

毛乌素沙地旱柳生长和生理特征对遮荫的反应

在一个控制试验中,旱柳经历了全不遮荫、部分遮荫和全部遮荫处理．比较了全不遮荫枝、全部遮荫枝、部分遮荫阳生枝(阳生枝)和部分遮荫阴生枝(阴生枝)的生长和生理特征,结果表明：阳生枝和全部遮荫枝的叶出生率和死亡率分别大于全不遮荫枝和阴生枝;遮荫处理明显影响净光合速率和夜间呼吸速率;阳生枝的分枝生物量、总校长度、枝叶生物量和枝叶重比显著大于全不遮荫枝,而阴生枝的分枝数、分枝生物量、叶面积、叶生物量、基茎、总校长度、枝叶生物量和枝叶重比都显著小于全部遮荫枝．