共查询到20条相似文献,搜索用时 31 毫秒
1.
Hongyan Dai Zhihong Zhang Xiuwu Guo 《In vitro cellular & developmental biology. Plant》2007,43(1):2-8
Hawthorn (Crataegus spp.) is an important plant with a long history as an ornamental and a source of medicine. A protocol is outlined for adventitious
bud regeneration from leaf and cotyledon explants of Chinese hawthorn (C. pinnatifida Bge. var. major N.E.Br.). Adventitious buds were induced on both the leaves of sprouting winter buds and the leaves of in vitro plants, but the percentage of bud regeneration from leaves of in vitro plants was very low—less than 6%. On N6 medium supplemented with 31.08 μM BA and 9.67 μM NAA, the percentages of bud regeneration
from leaves of sprouting winter buds of cultivars “Liaohong” and “Qiujinxing” were 31.4% and 17.6%, respectively. The regeneration
abilities of three kinds of cotyledon explants, immature cotyledon, mature cotyledon, and cotyledon leaf, were compared. The
percentage of bud regeneration from cotyledon leaves was higher. On MS media supplemented with 4.44 μM BA and 4.54–9.08 μM
TDZ, the percentages of bud regeneration from cotyledon leaves of cultivars “Qiujinxing” and “Xiajinxing” were 27.7 ± 7.8%
and 20.1 ± 4.7%, respectively, and the numbers of buds per explant were 5.9 ± 1.6 and 3.2 ± 0.7, respectively. On B5 medium
supplemented with 2.22 μM BA, 2.32 μM Kn, and 0.57 μM IAA, adventitious buds grew quickly and 80–100% of buds developed into
shoots. The shoots rooted successfully with the two-step rooting method. Ninety days after transplantation, more than 80%
plants were survived. This system of adventitious bud regeneration from leaf and cotyledon explants could be useful for the
genetic transformation and polyploidization of Chinese hawthorn. 相似文献
2.
The rooting capacity of leaves isolated from a vegetative clone ofAnagallis arvensis L. exposed to 9 hours of light (75 W m−2) at 22 °C and 15 hours of dark at 12 °C a day is significant only in F1 young leaves and not in adult ones. The rooting capacity of the young leaves and of the vegetative shoots is greater in longer
photoperiods. The leaves make roots even under weak (14 W m−2) irradiance. The rooting capacity of the leaves is diminished and even suppressed by exogenous sucrose (14,60 ×10−3M). This inhibition may be counteracted by IAA (10−6M). When leaves and shoots are taken from clones under long (16 h) photoperiods, or in constant irradiance, they progressively
lose their rooting capacity during the treatment. Rooting capaoity is regained if the clones are returned again to “short
day” (9 h) condition.
相似文献
3.
Regeneration abilities of buds on shoot segment explants isolated from adult trees of oak (Quercus robur), aspen (Populus tremula), black locust (Robinia pseudacacia), Japan pagoda tree (Sophora japonica), and English walnut (Ailanthus glandulosa) were studied during the growing season. Optimum BAP concentrations for the regeneration of oak bud meristems were dependent
on the date of sampling. Axillary shoots could be induced from winter and summer buds of oak and aspen on Dustan and Short
media supplemented with activated charcoal and BAP at concentrations from 0.5 to 2 mg 1-1. More intensive rooting of segments of newly formed shoots was observed on MS medium diluted to one half and supplemented
with 2 % sucrose and 0.2 mg 1−1 of IBA.Populus tremula formed longer axillary shoots on DS media supplemented with 0.5 mg 1−1 of BAP and 1 mg 1−1 of GA3.
Regeneration capacities of black locust, Japan pagoda tree, and English walnut were higher. In addition to the induction of
multiple shoots from buds, shoots could also be obtained from calluses formed on basal segment parts. Asparagine and glutamine
at a concentration of 25 mg 1−1 stimulated the percentage of differentiated stems on callus surface. Inhibitory effects of substances which accumulated in
buds in the second half of the growing season could be reduced by means of pulse treatments in 50 mg 1−1 BAP solutions or using short-term dipping into 0.1 % AgNO3 solution. 相似文献
4.
Lech Michalczuk 《Acta Physiologiae Plantarum》2002,24(2):131-136
Free and conjugated IAA levels were determined in wood, bark and cambial sap of M.9, M.26 and MM.106 apple rootstock genotypes
differing in growth vigour. The measurements were done on May 15th, June 15th and July 15th. The level of free IAA in bark and wood of the tested trees varied from 27.0 to 52.7 ng·g−1 f.w. while the conjugated hormone content averaged 3–5 times higher. In the bark and wood samples, the differences in auxin
content between rootstock genotypes and the time of stem harvesting were insignificant. The level of free IAA in cambial sap
was on average 10 to 20 times higher than in both bark and wood tissues, while the conjugated hormone level varied from none
(below detection limit) to 37 ng·g−1 f.w. Content of free IAA level in cambial sap from dwarf M.9 rootstock was significantly lower than that in either of the
more vigorous genotypes. In both vigorous rootstocks IAA level in cambial sap remained at a similar level at all sampling
dates but M.9 cambial sap showed a trend towards decreasing auxin content later in the growing season. 相似文献
5.
The hypocotyls, cotyledons, leaf blades, whole leaves and petioles of seedlings ofAilanthus altissima are capable of producing callus and budsin vitro. Buds and callus were also obtained from whole leaves and internodes of 2-years old plantlets grownin vitro. From the calli buds differentiated and later, both from buds developing directly without a callus phase and alsovia a callus phase, well developed shoots were formed. The cultures were mainained on MS medium in 2 combinations: A) IAA - 0.2
mg 1−1, BAP - 1 mg 1−1, GA3 - 0.5 mg 1−1, thiamine - 4 mg 1−1 and sucrose 3 %; B) BAP - 0.5 mg 1−1, IAA - 1 mg 1−1, casein hydrolysate 400 mg 1−1, thiamine 4 mg 1−1 and sucrose 3 %. Excised shoots, which had developedde novo in culture, produced roots when incubated on the basic mineral medium of MS with the addition of IAA. The regenerative potential
ofA. altissima is very high and this woody species seems to be an ideal object for various morphogenetic studies. 相似文献
6.
The effect of copper sulphate on differentiation and elongation of shoot buds from cotyledonary explants of Capsicum annuum L. cv X-235 was investigated. Shoot buds were induced on medium supplemented with 22.2 μM BAP and 14.7 μM PAA. Elongation
of shoot buds was obtained on MS medium containing 13.3 μM BAP + 0.58 μM GA3. Both shoot induction and elongation media were supplemented with different levels of CuSO4 (0–5 μM). The levels of CuSO4 in the induction as well as elongation medium highly influenced the shoot bud formation and their subsequent elongation.
Highest number of shoot buds per explant was obtained when the concentration of CuSO4 was increased 30 times to the normal MS level. Shoot buds formation frequency i.e., the number of shoots formed per explant
was increased two fold as compared to those formed on control. Elongation both in terms of percentage and length of shoots
was better than that on control. Healthy elongated shoots were rooted on MS medium supplemented with 5.7 μM IAA. Rooted plantlets
were transferred to field conditions. 相似文献
7.
An efficient in vitro propagation of kava (Piper methysticum) was established. Utilizing 15-d-old tender shoots from dormant auxiliary buds as explants, significant induction of vigorous
aseptic cluster shoots was achieved in Murashige and Skoog (MS) medium containing 0.5 mg dm−3 6-benzyladenine (BA), 0.5 mg dm−3 indole-3-acetic acid (IAA), and antibiotics after 30 d. In vitro rooting was achieved at 100 % efficiency in MS medium containing 0.75 to 1.00 mg dm−3 IAA or indole-3-butyric acid and 3 % sucrose. The most robust and long roots were observed in medium with IBA. Moreover,
the embryonic callus was induced from petioles in MS medium supplemented with 1.0 mg dm−3 BA and 0.1 mg dm−3 IAA, of which 70 % differentiated into shoots in the presence of 1.0 mg dm−3 BA and 0.5 mg dm−3 IAA. 相似文献
8.
Rapid clonal multiplication of Aegle marmelos (L.) Corr. (Rutaceae), a medicinal tree, was achieved by enhanced axillary bud proliferation in young single-node segments
of a 25-year-old tree cultured in Murashige and Skoog (MS) nutrient medium. Bud break was dependent on cytokinin supply, but
the synergistic combination of 2.5 mg l–1 6-benzylaminopurine (BAP) and 1.0 mg l–1 indole-3-acetic acid (IAA) induced the formation of 12.1 shoots of up to 5.2 cm length in 48% of the explants after 7 weeks
of culture. Explants of in-vitro-grown shoots – node, whole leaf, shoot tip and internode – were subcultured in the presence
of 0.05–2.5 mg l–1 BAP to produce 11.3, 18.4, 5.3 and 3.2 shoots and shoot buds at a 100%, 70%, 95% and 40% rate respectively, in 7 weeks. Different
shoot nodes and leaves were equally regenerative and adventitious organogenesis in the latter was confined to cut petiolar
ends. Nodal explants responded most favourably at low BAP (0.05–0.1 mg l–1) and produced uniform (3.8–5.3 cm) shoots facilitating their simultaneous harvest for rooting. Repeated subculturing through
five cycles of nodes and leaves of shoot cultures enabled continuous production of healthy callus-free shoots without any
sign of decline. Shoot cuttings (3.0–5.2 cm) were best rooted in half-strength MS medium with 0.5 mg l–1 IAA (70%) or 10.0 mg l–1 indole-3-butyric acid (90%). Eighty-eight percent of the rooted plants were established in polybags after hardening.
Received: 4 April 1996 / Revision received: 8 September 1997 / Accepted: 20 September 1997 相似文献
9.
Triploid plants of ornamental Phlox drummondii Hook. were raised from cultures of endosperm excised from immature fruits having zygotic embryo at early dicotyledonous stage. Endosperm tissue was firstly cultured with the embryo on the Murashige and Skoog’s (MS) medium supplemented with 5 μM 6-benzylaminopurine (BAP) + 10 μM α-napthaleneacetic acid (NAA) for 7 d and recultured after the embryo was removed. A friable callus appeared two weeks after removal of the embryo and it became compact callus mass in another three weeks. Upon transfer of this 5-week-old callus to the MS medium with 10 μM BAP + 2.5 μM indole-3-acetic acid (IAA), maximum percentage of green nodular shoot buds appeared from which regenerated dwarf shoots. Elongation of the dwarf shoots, however, required transfer of the individual dwarf shoots excised from the callus on the fresh medium and best results achieved on medium with low concentration of IAA (0.5 μM) in presence of 10 μM BAP. The shoots were then rooted in vitro and plants subsequently established in pots containing soil. Over 70 % of plants were triploid with a chromosome number of 2n=3x=21. Size of stem, leaves, flowers, pollen, and stomata of these triploid plants were higher and the plants were more vigorous as compared to naturally occurring diploid plants. In particular, flowers showed bright colour with enlarged central eye adding to their ornamental value. 相似文献
10.
An efficient regeneration protocol for genetic transformation was developed from the leaves of an 11-year-old Phtinia × fraseri “Red Robin” tree. A high frequency of adventitious buds (88.63 ± 1.38%) and the highest maximum mean number of adventitious
buds per explant (4.65 ± 0.48) were obtained in light conditions on Murashige–Skoog (MS) medium containing 2 mg l−1 benzyladenine (BA) and 0.2 mg l−1 α-Naphthaleneacetic acid (NAA). After preculturing for 6 days, over 95% of the shoots successfully rooted on 1/2 MS medium
supplemented with 0.3 mg l−1 indole-3-butyric acid (IBA) within 3 weeks. For genetic transformation, two crucial parameters (30 mg l−1 kanamycin for selection and 30-min suspension time) were optimized. Taken together, a reliable transformation system with
an efficiency of more than 5% was established. This genetic transformation protocol can be utilized for further genetic manipulation
of the Photinia tree. 相似文献
11.
A process with controlled pattern of regenerant differentiation from leaflet segments leading to production of cloned plants
of a 40-year-old tree of Azadirachta indica was developed. A two-step procedure was adopted for containing intervening callusing during regenerant differentiation using
modified Murashige and Skoog (MS) medium, where in the first step the explants were subjected to pulse treatments having higher
concentration of 6-benzylaminopurine (BAP), while in the second step they were cultured in one-tenth of the initial concentrations
of BAP. In the present case, simultaneous differentiation of two types of morphogenetic structures, that is, shoot buds and
the meristematic nodules was observed. However, differentiation of higher number of desirable regenerants—the shoot buds and
a few meristematic nodules, rather than vice-versa could be controlled by increasing both, the concentration of BAP in pulse
treatment and the duration of pulse treatment. In the optimum treatment, where the explants were exposed to 8.88 μM BAP and
81.43 μM adenine hemisulphate for 5 days followed by their transfer to 0.88 μM BAP and 81.43 μM adenine hemisulphate, on an
average, 17.4 shoot buds and only 1.6 meristematic nodules were formed from a leaflet. On subculturing, the shoot buds developed
into shoots, whereas the meristematic nodules produced three kinds of organized structures that too in varied proportions.
Multiplication of shoots was sustained in proliferation medium supplemented with 1.11 μM BAP, 1.43 μM indole-3-acetic acid
(IAA) and 135.72 μM adenine hemisulphate. The isolated shoots were rooted and complete plantlets were transferred to potted
soil with 100% survival. 相似文献
12.
The tryptophan auxotroph mutant trp3-1 of Arabidopsis thaliana (L.) Heynh., despite having reduced levels of l-tryptophan, accumulates the tryptophan-derived glucosinolate, glucobrassicin and, thus, does not appear to be tryptophan-limited.
However, due to the block in tryptophan synthase, the mutant hyperaccumulates the precursor indole-3-glycerophosphate (up
to 10 mg per g FW). Instability of indole-3-glycerophosphate leads to release of indole-3-acetic acid (IAA) from this metabolite
during standard workup of samples for determination of conjugated IAA. The apparent increase in “conjugated IAA” in trp3-1 mutant plants can be traced back entirely to indole-3-glycerophosphate degradation. Thus, the levels of neither free IAA
nor conjugated IAA increase detectably in the trp3-1 mutant compared to wild-type plants. Precursor-feeding experiments to shoots of sterile-grown wild-type plants using [2H]5-l-tryptophan have shown incorporation of label from this precursor into indole-3-acetonitrile and indole-3-acetic acid with
very little isotope dilution. It is concluded that Arabidopsis thaliana shoots synthesize IAA from l-tryptophan and that the non-tryptophan pathway is probably an artifact.
Received: 1 March 2000 / Accepted: 10 April 2000 相似文献
13.
Stem internodes with axillary buds were excised from 5-year old trees ofFicus benjamina cv. Exotica. The effect of 6-benzylaminopurine (BAP), gibberellic acid (GA3), indole-3-acetic acid (IAA), naphthaleneacetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D) on shoot growth and
proliferationin vitro was investigated. Multiple shoots were developed after 3–4 weeks from stem internodes with axillary buds incubated in Murashige
and Skoog (MS) medium supplemented with phloroglucinol (PG) and BAP. Optimum shoot proliferation took place in the presence
of 1.0 mg l−1 BAP. Shoots obtained could be elongated in a medium with 0.5 mg l−1 GA3 prior to their rooting. The root initiation was successfully induced on MS medium either with IAA at 0.5–0.1 mg l−1 or in plant growth regulator-free medium. All rooted plantlets were subsequently transferred to a peat, humus and perlite
mixture in a culture room with high humidity and covered with plastic bags. After one month the plantlets were established
for growing in a greenhouse.
Communicated by J. TUPY 相似文献
14.
Sugarcane plants were grown in sandculture from15N stem cuttings approximately 3 cm long with one node (“nodes”) or 15 cm long, with two nodes (“seedpieces”), in nutrient
solution without or with 8 mM of N. The decrease in the15N enrichment of plants growing in zero-N solution relative to the initial15N enrichment of the cuttings indicated N2 fixation. The contribution from atmospheric dinitrogen to the total N of the plants amounted to 9.3% for those growing from
nodes and 15.2% for those growing from seedpieces after 90 and 60-day growth periods, respectively. Most of the fixed nitrogen
went to the root-N pool. From 9 to 39% of the N initially present in the stem cuttings was lost from the plants while about
45% of the remaining N was translocated to the shoots and roots during a 30-day growth period for seedpieces and a 15-day
growth period for the nodes. More than 85% of the translocated N went to the shoots. At the end of a 60-day growth period
(for nodes and seedpieces, respectively) about 35% of the initial N remained in the stem cuttings, irrespective of type of
cutting or of the presence or absence of N in the nutrient solution. 相似文献
15.
S. Y. Park Y. W. Kim H. K. Moon H. N. Murthy Y. H. Choi H. M. Cho 《Plant Cell, Tissue and Organ Culture》2008,93(3):341-346
The effect of phytohormones on the breaking of dormancy of axillary buds in Salix pseudolasiogyne and their subsequent proliferation from nodal explants were examined. Nodal explants obtained from a 20–year-old S. pseudolasiogyne tree were cultured either on woody plant basal medium (WPM) or WPM supplemented with benzyladenine (BA, 2.2/4.4 μM), zeatin
(1.1/2.2 μM), gibberillic acid (GA3, 2.9 and 14.5 μM), and GA3 + BA (2.9 + 4.4 μM). Although axillary shoots developed in all the media, a higher percentage bud break occurred on BA supplemented
media. To corroborate the results, endogenous levels of cytokinins [Cks, N
6-isopentenyladenine (iP), zeatin riboside (t-ZR), dihydrozeatinriboside (DHZR)] and abscisic acid (ABA) were determined. On BA supplemented media, the levels of zeatin
type (Z-type) of Cks were higher than those of isopentenyladenine type of Ck in the explants, while the ABA level was low.
Axillary shoots did not grow well and became necrotic upon subculture to fresh basal WPM. In order to improve shoot growth,
they were subcultured twice at a 4-week interval on to WPM supplemented with BA (2.2/4.4 μM), GA3 (1.4 μM), or GA3 + BA (1.4 + 4.4/2.9 + 4.4 μM). Maximal shoot growth (93%) was achieved on WPM supplemented with 2.2 μM BA. Comparative analyses
of endogenous Cks revealed that higher Cks (Z-type Cks) were present in actively growing shoots. Rooting was readily achieved
when the shoots were subcultured to WPM without phytohormones. The rooted plants were acclimatized well upon transplantation. 相似文献
16.
Gonasageran Naidoo 《Trees - Structure and Function》2010,24(4):667-673
In this investigation, morphological and physiological differences between fringe and dwarf Avicennia marina (Forsk.) Vierh. growing in seawater and hypersalinity were compared along a tree height and productivity gradient in Richards
Bay, South Africa. Dwarf trees had thicker leaves and cuticles, lower specific leaf area and salt gland frequency, while the
concentrations of total chlorophyll and chlorophylls a and b were lower by 26, 23 and 39%, respectively, compared to fringe
trees. Soil ψ and soil salinity were −3.04 ± 0.09 MPa and 36 ± 3 psu in the fringe zone, compared to −7.24 ± 0.38 MPa and
58 ± 5 psu, respectively, in the dwarf zone. Midday minimum xylem ψ was −4.3 ± 0.23 MPa in the fringe zone and −6.4 ± 0.28 MPa
in the dwarf zone. In leaves of dwarf trees, the concentration of Na+ was 30% higher, while those of K+, Ca2+ and Mg2+ were lower by 41, 38 and 55%, respectively, than fringe trees. The Na+/K+ ratio of leaves was 2.1 ± 0.03 for fringe and 5.6 ± 0.05 for dwarf trees. Rates of secretion of Na+, Cl−, K+, Ca2+ and Mg2+ over 24 h were significantly lower in dwarf trees by 44, 45, 78, 66 and 54%, respectively. In fringe trees, the rate of secretion
of Na+ and Cl− was about 28% higher during the night than during the day, while in dwarf trees the corresponding increase was about 174%.
CO2 exchange, leaf conductance, quantum yield of PS II, ETR through PSII and intrinsic photochemical efficiency of PS II were
significantly lower in dwarf trees by 50, 83, 39, 33 and 12%, respectively. 相似文献
17.
Melike Bor Ozden Ozkur Filiz Ozdemir Ismail Turkan 《Plant Molecular Biology Reporter》2009,27(4):518-525
Myrosinase (EC 3.2.1.147) catalyzes cleavage of glucosinolates, which consist of a thioglucoside moiety linked to amino acid-derived
side chains. Myrosinase activity and expression profiles were investigated together with glucosinolate contents in Capparis ovata (caper) in order to characterize the glucosinolate–myrosinase system. The desulfoglucosinolates—glucocapparin, glucoiberin,
progoitrin, epiprogoitrin, sinigrin, gluconapin, glucosinalbin, and glucobrassicin—were extracted and quantified from leaves,
seeds, flowers, flower buds, and young shoots. The major desulfoglucosinolate was glucocapparin, which accumulated to values
of 39.35 ± 0.09 and 25.56 ± 0.11 μmol g−1 dry weight in seed and leaf extracts, respectively. Myrosinase has high activity in caper seeds, leaves, flowers, and flower
bud tissues having the highest total activities in seed extracts (79.23 ± 0.18 U). However, specific activities were the highest
in flower bud extracts (200.44 ± 0.09 U mg−1 protein). The myrosinase protein migrated as a single band with a molecular weight of 65 kDa on sodium dodecyl sulfate polyacrylamide
gel electrophoresis and on Western blots probed with the myrosinase-specific 3D7 antibodies. Native gel electrophoresis revealed
two putative myrosinase isoenzymes in seeds, leaves, and flower tissues. The caper homolog of the Arabidopsis thaliana TGG1 gene was differentially expressed in seeds, leaves, flowers, and flower buds with the highest expression levels in leaves
and flower bud tissues. 相似文献
18.
The present study aims at providing standard values for the exploration type (ET)-specific quantification of extramatrical
mycelium (EMM) of ectomycorrhizal fungi applicable to ecological field studies. These values were established from mycelial
systems of ectomycorrhizae (ECM) synthesized in rhizotrons with near-to-natural peat substrate. Based on image analysis, the
“Specific Potential Mycelial Space Occupation” (sPMSO), i.e. the ET-specific complete area that is covered by the EMM systems
(mm2 cm−1 ECM−1), and the “Specific Actual Mycelial Space Occupation” (sAMSO), i.e. the projection area of mycelial systems (mm2 cm−1 ECM−1), were analyzed as an extension of a previously described approach. The “Specific Extramatrical Mycelial Length” (sEML) [m
cm−1 ECM−1] and the “Specific Extramatrical Mycelial Biomass” (sEMB) (μg cm−1 ECM−1) were calculated for each of the ET via the proportion of hyphal projected area, hyphal length and biomass, the latter two
being derived from previous measurements on Piloderma croceum, a “Medium-Distance” (MD)-ET. Both sPMSO and sAMSO were highest for the “Long-Distance” (LD)-ET, whereas those of the “Short-Distance”
(SD)-ET and MD-ET were similar, although showing high variation. In contrast, mycelial density per occupied area of the MD-ET
was twice as high as that of the LD-ET. Proportional to the sAMSO, the EMM length and biomass differed considerably between
the three ET with values of the MD-ET being 1.9 times higher than those of SD-ET, and those of the LD-ET being 15 times higher
than those of the SD-ET. These standards in relation to ECM length may ease quantification of mycelial space occupation and
biomass in a relatively simple way. Thereby, the ET-specific contribution of EMM can be distinguished—also of non-cultivable
species—and up-scaling to large-scale estimation of cost/benefit relations is possible. 相似文献
19.
Comparison of growth and gibberellin concentrations in shoots from orchard-grown standard and thermosensitive dwarf apple trees 总被引:1,自引:0,他引:1
Apple (Malus domestica Borkh.) trees were propagated by budding from selected fully grown hybrids that ranged in height from 1.5 to 8 m. The growth and development of the selected budded trees after 7 years in the orchard was similar to that of the parent trees. Additional grafting studies showed that the dwarfism was not associated with the roots. Differences in photosynthetic activity and associated processes were not related to the size difference between tissue culture-propagated orchard-grown standard cv. Golden Delicious and dwarf hybrid trees. Applications of GA3 did not stimulate elongation of shoots of dwarf trees. Shoots of both standard and dwarf trees started to develop in mid-April when they contained nearly the same amounts of GA1, GA3 and GA8, but standard shoots contained higher concentrations of GA19, GA20 and GA29. On 2 June standard shoots were almost three times the length of dwarf shoots, but the number of leaves and area per leaf were nearly the same. The relative amounts of GAs on 12 May and 2 June for both plant types were similar to those on 20 April, except that GA19, GA20, GA1 and GA29 levels had declined. Gibberellin levels in standard shoots declined further between 2 and 22 June, after which there was no further shoot elongation or production of new leaves. Between 2 June and the end of the growing season, when summer temperatures were high, dwarf shoots continued to elongate slowly and to develop new leaves, which expanded little. During this time, the GA19 content of dwarf shoots nearly doubled, whereas the amounts of GA20, GA1, GA29 and GA8 declined. By the end of the season, standard shoots were 40 cm in length with 20 leaves and dwarf shoots were 28 cm in length, but with 36 leaves. High summer temperatures appear to induce loss of GA-responsiveness in orchard-grown dwarf trees and to cause a reduced rate of conversion of GA19 to GA20 in these genotypes. 相似文献
20.
Leafing pattern has long been considered as an important element characterizing the growth strategy of tree species; however,
the consequences of leafing pattern for tree-crown formation have not been fully understood. To address this issue, the dynamic
events (growth, birth, and death) of current-year shoots and leaves were investigated together with their location in saplings
of a pioneer tree, Alnus sieboldiana. The leafing pattern was characterized by successive emergence and shedding of short-lived leaves. The combination of successive
leafing and within-crown variation in leaf production brought about characteristic outcomes in crown morphology. In the outer
crown, because of continuous leaf production, the shoots achieved great extension and enormous daughter shoot production,
resulting in rapid expansion of the crown. In contrast, in the inner crown, due to early termination of leaf production, the
shoots completely lost their leaves early in the growing season and consequently themselves died and were shed within the
season. Such quick shedding of shoots caused “crown hollowing”, i.e., the interior crown consisted of primary branches with
little secondary development or foliage. These dynamic features are an effective adaptive strategy in early succession but
also may be a disadvantage to maintaining foliage for longer period. Crown maintenance associated with the longevity of structural
components is thought to play an important role in survival strategy of tree species. 相似文献