- Email: [email protected]
Shoot Apical Organization in Acacia nilotica (L.) Delile
Flora (1983) 174: 467-473
Shoot Apical Organization in Acacia nilotica (L.)
DELILE
A. PILLAI and KAILASH CHANDRA SHARMA Department of Botany, University of. Rajasthan, Jaipur, India
Summary The vegetative apices have a tunica-corpus organization and no cytohistological zonation. The corpus is divided into a central mother cell zone (CMZ), peripheral zone (PZ) and pith meristem (PM) based on analysis of the cell net. The tunica is 2-layered, the clarity of the layers depending on the plastochronic stage. The CMZ shows a decrease in depth from the minimal to the maximal stage of the plastochron. The inflorescence and floret apices show a mantle-core organization. In the young reproductive apex the axial cells of the mantle are ligthly stained. The complete inflorescence apex is used up in the production of bracts and florets.
Introduction The past few decades witnessed significant advances in our knowledge of the origin, organization and behaviour of apical meristems (cf. CROSS 1939; GIFFORD 1943; HARA 1963; SMITH 1963; ENGLAND & TOLBERT 1964; AGARWAL & PURI 1977; SWAMY & KRISHNAMUTHY 1978; KAVATHEKAR & PILLA! 1980 and PILLAI & CHACKO 1980). Data from an year round study of the shoot apex in Albizia lebbek (L.) BENTH. were reported by PILLAI & KAILASH (1982). This is a report on a seasonal study of the shoot apical organization in Acacia nilotica (L.) DELILE.
Materials and Methods The shoot apices were collected in the first week of every month round the year from a few selected trees of Acacia nilotica growing in the University campus. They were fixed in FAA and after the normal processing through TBA series, serial longitudinal sections were cut at 7-8 ,um. Sections were stained with safranin, light green and tannic acid-iron chloride combination (JoHANSEN 1940). Width of the shoot apex and height of the apical dome and youngest leaf primordium were measured and plastochronic index was calculated following previous pUblications (PAOLILLO & GIFFORD 1961 and PILLA! & KAVATHEKAR 1975).
Observations Acacia nilotica flowers twice a year - during March-April and August-September. More profuse flowering occurs during the latter season than the former. At flowering, reproductive and vegetative shoots continue to develop simultaneously, the former from the axillary buds whereas the terminal buds ramain mostly vegetative. The vegeta.tive apex shows:3o tunica, corpus organization. The tunica is 2-layered. A weak cytohistological zonation was observed in apices at maximal stase of the plas-
468
A.
PILLAI
and K. C.
SHARMA
469
Shoot Apical Organization
Table 1. Height and diameter of the shoot apices and depth of CMZ and mature pith at different plastochronic stages (Average of 16 apices) Plastochronic stage
Minimal Mid Maximal
Height of dome
Width of dome
Height of youngest leaf primordium
({lm)
({lm)
({lm)
35.6 37.5 71.6
94.0 101.2 133.2
14.8 50.4 209.1
Plastochronic Index
2.600 0.773 0.357
Depth at Depth of which CMZ mature pith occurs ({lm)
({lm)
52.0 47.0 42.6
23.47 22.30 20.00
tochron (Fig. 3). Based on an analysis of the cell net the corpus may be demarcated into zones viz., central mother cell zone (CMZ), peripheral or flanking zone (PZ) and pith meristem (PM). Apices in May, June, December and January show an increase in size whereas samples in March, April, July and August show a decrease (Fig. 8). The apices were assigned to three plastochronic stages (Figs. 1-3) and the plastochronic index and depth of the CMZ and PM at different plastochronic stages are given in Table 1. Minimal stage: The shoot apex is a low, broad dome. The 2-layered tunica is composed of uniformly stained cells. Disturbances in the regular arrangement of the cells indicate divisions in various planes. The PZ with slightly regularly arranged cell layers is clear on the side opposite the youngest leaf primordium. A group of 8-9 cells subjacent to the CMZ represent the pith meristem subjacent to which are the longitudinal files of differentiating pith (Fig. 1). Mid stage: The tunica is 2-layered. Dome size increases and the depth of CMZ shows a slight decrease. The major portion of this zone is above the level of attachment of the youngest leaf primordium. The PZ shows about 3-4 cell layers on both flanks (Fig. 2). Maximal stage: Size of the apical dome shows a further increase, the increase in height being more. The tunica has two cell layers. The CMZ shows a further decrease in its depth. Periclines in cell layers underlying the outer tunica layer on the flank indicate the site for the next leaf primordium. The PZ is well developed with 3-5 regular cell files. The cells of PM occur in vertical files followed proximally by the differentiating pith (Fig. 3). Reprod ucti ve apex: During the flowering season most of the axillary buds develop into inflorescence apices. The inflorescence is a globose head and produces
Figs. 1-3. Median longitudinal sections of vegetative shoot apices at different plastochronic stages. Fig. 1. Minimal, X 500 Fig. 2. Mid, X 375 Fig. 3. Maximal, X 375 30 Flora, Bd. 174
470
A.
PILLA!
and K. C.
SHARMA
Figs. 4-7. Median longitudinal sections of reproductive apices. Fig. 4. Young inflorescence apex, X 315. Fig. 5. Inflorescence apex with bract and floret primordia at different developmental stages, X315. Fig. 6. Inflorescence apex with young bracts and axillant florets, X 90. Fig. 7. Floret apex, X 450.
bracts and axillant floral primordia acropetally (Fig. 5). The enlargement of the apex is followed by the establishment of a broad lightly chromophilic, large celled core covered by a multilayered mantle of densely chromophilic cells. The tunica, PZ as well as the CMZ are involved in the formation of the mantle layers, the major contribution being from the PZ. The mantle of the young inflorescence apex shows an axially located group of lightly stained cells which is not observed when bracts start developing (Fig. 4). The bract primordia are initiated when the inflorescence apex measures about 168 and 188 pm in height and diameter respectively. The cells in the inner mantle layers at the site of bract production are more densely stained than other mantle cells and start dividing in all planes. The outermost mantle layer cells divide by rapid anticlinal divisions. When the bract develops to a height of about 20 pm, the axillary fl~ret primordia also develop a mantle-core organization (Figs. 6, 7).
Shoot Apical Organization
471
D-DIAMETER
140
.-HEIGHT
3.., ~
0
120
100
0
-'
«
u 80 ii: <{
Lo..
0
60
Ul
z
0
iii 40
..,Z ~
0
20
0
ACACIA Fig. 8. Histogram depicting dimensions of vegetative shoot apices from monthly collections. (AZ - Axial zone; B -- Bract; BP - Bract primordium; CMZ - Central mother cell zone; F _ Floret; FP - Floret primordium; LP - Leaf primordium; M - Mantle; PE - Periclines; PM - Pith meristem; PZ - Peripheral zone; T - Tunica; T 1 , T2 - Tunica layers).
The floret primordia grow to a height of about 88 [tm and measure 80 [tm in diameter before the initiation of floral parts. The whole inflorescence apex is used up in flower formation and no residual meristem has been observed (Fig. 6). Only the mantle layers seem to be involved in the formation of bract and floret primordia. The latter develop a mantle-core configuration followed by the initiation of sepals, petals, stamens and carpels. The mantle shows 3-4 chromophilic cell layers and divisions in the mantle are responsible for the origin of floral parts (Fig. 7).
Discussion Analysis of the shoot apical meristem all round the year has helped consolidate inter-related aspects of shoot development. There are conflicting views about correlation between size and shape of the apex and growth habit. The data presented here support ROUFFA & GUNCKEL (1951) and fail to establish any correlation between shape and size of apex and growth habit of the plant.
In tree species there are many reports of a well marked cytohistological zonation in the shoot apex (GIFFOltD 1950; TOLBERT & JOHNSON (1966) and AGARWAL & PURl (1977» as well as reports denying the presence of zonation (RAMJI 1960; TUCKER (1962) and KAVATHEKAR (1976». The present study using anatomical stains failed to bring 30·
A. PILLAI and K. C. SHARMA
472
out differences in stainability between zones, whereas histochemical localization of RNA, total proteins and histones brought out a zonate distribution pattern (SHARMA et al. 1982). This supports the demarcation of the corpus into zones on the basis of cell net analysis. The gradual decrease in depth of theCMZ from minimal to the maximal stage of the plastochron indicates that cells from this zone become part of the PZ and PM during the plastochronic cycle. HAGEMANN (1960) reported that in Peperomia the flank meristem was renewed directly from cells of the apical initial zone at each plastochron. Measurements of apex size round the year bring out higher values during November to January and lowest values during seasons of active growth and elongation. This agrees with GIFFORD'S (1950) data on some woody ranales that maximum size may be correlated with active appandage formation rather than with shoot elongation. BONNAND (1959) in Nicotiana, CORSON & GIFFORD (1969) in Datura and GOYAL (1981) in Papaver species reported a lighter stained axial region in the reproductive apex. The early reproductive apex in Acacia also shows a similar zone though it does not persist in the older inflorescence apex producing bract and floret primordia. PLANTEFOL (1957) suggested that the anneau initial and meristeme d'attente may play different roles at flowering depending upon whether a terminal flower is produced or not. But data collected in this laboratory do not seem to support this. The floral apex in Papaver species producing a solitary flower, Sesamum with a cymose inflorescence (GOYAL 1981), Lantana which forms a flattened recemose inflorescence (GOYAL et al. 1981) and the present data on Acacia - all show a lighter stained axial region in the inflorescence and/or floral apex. Later in development, a uniform mantle region is formed over a central core involving the reorganization of all zones of the apex, rather than the stimulation of a previously inactive zone as suggested by adherents of the French school ofthought. In considerations ofthe proposed equivalence between the meristeme d'attente in the shoot and the quiescent centre in the root apex (SWAMY & KRISHNAMURTHY 1978), the observed differences lie probably in the very nature of the shoot apex in relation to the production of lateral organs and conversion to limited growth at flowering.
Acknowledgements The authors gratefully acknowledge the keen interest shown in the manuscript preparation by Prof. S. K. PILLAr. One of us (K.C.S.) is also thankful to the Head, Department of Botany for providing facilities.
References AGARWAL, R. M., & PURl, V. (1977): Ontogenetic studies in some important timber trees of India. I _ Shoot apex organization and leaf development in Dalber'gia SiS800. Phytomorphology 27: 296-302.
L. (variete white burley) en apex inflorescential. C.R. hebd. Seanc. Acad. Sci. Paris 248: 1209-1211. CORSON, G. E., & GIFFORD, E. M. Jr. (1969): Histochemical studies of the shoot apex of Datura stramonium during transition to flowering. Phytomorphology 19: 189-196.
1) BONNAND, J. (1959): Transformation de l'apex vegetatif de l"';1;cotiana. tabacum
Shoot Apical Organization
47~
CROSS, G. L. (1939): The structure and development of the apical meristem in the shoots of Taxodium distichum. Bull. Torrey bot. Club 66: 431-452. ENGLAND, W. H., & TOLBERT, R. J. (1964): A seasonal study of the vegetative shoot apex of Myriophyllum heterophyllum. Am. J. Bot. 51: 349-353. GIFFORD, E. M. Jr. (1943): The structure and deyelopment of the shoot apex of Ephedra altissima. DESF. Bull. Torrey bot. Club 70: 15-25. - (1950): The structure and development of the shoot apex in certain woody Ranales. Am. J.: Bot. 37: 595-611. GOYAL, S. C. (1981): Anatomical and morphological studies on some oil-yielding plants. Ph.D. thesis, Univ. Rajasthan, Jaipur. GOYAl" V., SHARMA, M., & PILLAI, A. (1981): Developmental studies on the shoot apex of Lantana camara L. In: Fourth Botanical Conference, Calicut University, Calicut. Abstract no. 59. 1) HAGEMANN, W. (1960): Kritische Untersuchungen liber die Organisation des Sprossscheiteis dikotyler Pflanzen. Osterr. Bot. Z. 107: 366-402. HARA, N. (1963): Structure of the shoot apex with special reference to Chimera formation. Gamma field symposia, Japan 12: 97-112 . •TOHANSEN, D. A. (1940): Plant microtechnquie. McGraw Hill Co., New York. KAVATHEKAR, K. Y. (1976): Anatomical studies on some Ranales. Ph.D. Thesis, Univ. Rajasthan, Jaipur. & PILLA I, A. (1980): Studies on the developmental anatomy of Ranales. VII. Shoot apical organisation in some members of Annonaceae. Flora 169: 245-253. PAOLILLO, D .•T. Jr., & GIFFORD, E. M .•Jr. (1961): Plastochronic changes and the concept of apical initials in Ephedra altissima. Am. J. Bot. 4S: 8- -16. PILLAI, A., & KAILASH (1982): Developmental anatomy of Albizia lebbek. I. Shoot Apex. Acta Bot. Indica 10: 79-S4.
-
& KAvA'rHEKAR, K. Y. (1975): Apical meristems in Nymphaea stellata WILLD. Proc. Indian Acad. Sci. SIB: 91-100. PILLAI, S. K., & CHACKO, B. (1978): Growth periodicity and structure of the shoot apex of Picea smithiana (WALL.) BOlSS. An anatomical and histochemical stUdy. Flora 167: 515-524. 1) PLANTEFOL, L. (1957): Sur deux notes relatives a l'ontogenie d'inflorescences. C. R. Acad. Sci. Paris 245: 503-607. -
RAMJI, M. V. (1960): The structure of the shoot apex and leaf initiation in Polyalthia longifolia. Proc. Indian Acad. Sci. 5IB: 227-241. ROUFFA, A. S., & GUNCKEL, J. E. (1951): A comparative study of vegetative shoot apices in the Rosaceae. Am. J. Bot. 3S: 301-307. SHARMA, K., SHARMA, M., & PILLAI, A. (1982): Histochemical analysis of zonation in .the shoot apex of Acacia nilotica. J. Indian Bot. Soc. Communicated. SMITH, C. A. (1963): Shoot apices in the family Moraceae with a seasonal study of Maclura pomifera (RAF.) SCHNEID. Bull. Torrey bot. Club 90: 237-25S. SWAMY, B. G. L., & KRISHNAMURTHY, K. V. (1978): Certain conceptual aspects of meristems. III. A model. Phytomorphology 28: 1-7. TOLBERT, R. J., & JOHANSEN, M. A. (1966): A survey of the vegetative shoot apices in the family Malvaceae. Am. J. Bot. 53: 961-970. TUCKER, S. C. (1962): Development and phyllotaxis of the vegetative axillary bud of Michelia fuscata. Am. J. Bot. 50: 661-66S. 1) Not seen in original
Received October 5, 1982 Authors' address: Dr. A. PILLAI and K. C. SHARMA, Department of Botany, University of Rajasthan, Jaipur - 302004, India.
Shoot Apical Organization in Acacia nilotica (L.)
DELILE
A. PILLAI and KAILASH CHANDRA SHARMA Department of Botany, University of. Rajasthan, Jaipur, India
Summary The vegetative apices have a tunica-corpus organization and no cytohistological zonation. The corpus is divided into a central mother cell zone (CMZ), peripheral zone (PZ) and pith meristem (PM) based on analysis of the cell net. The tunica is 2-layered, the clarity of the layers depending on the plastochronic stage. The CMZ shows a decrease in depth from the minimal to the maximal stage of the plastochron. The inflorescence and floret apices show a mantle-core organization. In the young reproductive apex the axial cells of the mantle are ligthly stained. The complete inflorescence apex is used up in the production of bracts and florets.
Introduction The past few decades witnessed significant advances in our knowledge of the origin, organization and behaviour of apical meristems (cf. CROSS 1939; GIFFORD 1943; HARA 1963; SMITH 1963; ENGLAND & TOLBERT 1964; AGARWAL & PURI 1977; SWAMY & KRISHNAMUTHY 1978; KAVATHEKAR & PILLA! 1980 and PILLAI & CHACKO 1980). Data from an year round study of the shoot apex in Albizia lebbek (L.) BENTH. were reported by PILLAI & KAILASH (1982). This is a report on a seasonal study of the shoot apical organization in Acacia nilotica (L.) DELILE.
Materials and Methods The shoot apices were collected in the first week of every month round the year from a few selected trees of Acacia nilotica growing in the University campus. They were fixed in FAA and after the normal processing through TBA series, serial longitudinal sections were cut at 7-8 ,um. Sections were stained with safranin, light green and tannic acid-iron chloride combination (JoHANSEN 1940). Width of the shoot apex and height of the apical dome and youngest leaf primordium were measured and plastochronic index was calculated following previous pUblications (PAOLILLO & GIFFORD 1961 and PILLA! & KAVATHEKAR 1975).
Observations Acacia nilotica flowers twice a year - during March-April and August-September. More profuse flowering occurs during the latter season than the former. At flowering, reproductive and vegetative shoots continue to develop simultaneously, the former from the axillary buds whereas the terminal buds ramain mostly vegetative. The vegeta.tive apex shows:3o tunica, corpus organization. The tunica is 2-layered. A weak cytohistological zonation was observed in apices at maximal stase of the plas-
468
A.
PILLAI
and K. C.
SHARMA
469
Shoot Apical Organization
Table 1. Height and diameter of the shoot apices and depth of CMZ and mature pith at different plastochronic stages (Average of 16 apices) Plastochronic stage
Minimal Mid Maximal
Height of dome
Width of dome
Height of youngest leaf primordium
({lm)
({lm)
({lm)
35.6 37.5 71.6
94.0 101.2 133.2
14.8 50.4 209.1
Plastochronic Index
2.600 0.773 0.357
Depth at Depth of which CMZ mature pith occurs ({lm)
({lm)
52.0 47.0 42.6
23.47 22.30 20.00
tochron (Fig. 3). Based on an analysis of the cell net the corpus may be demarcated into zones viz., central mother cell zone (CMZ), peripheral or flanking zone (PZ) and pith meristem (PM). Apices in May, June, December and January show an increase in size whereas samples in March, April, July and August show a decrease (Fig. 8). The apices were assigned to three plastochronic stages (Figs. 1-3) and the plastochronic index and depth of the CMZ and PM at different plastochronic stages are given in Table 1. Minimal stage: The shoot apex is a low, broad dome. The 2-layered tunica is composed of uniformly stained cells. Disturbances in the regular arrangement of the cells indicate divisions in various planes. The PZ with slightly regularly arranged cell layers is clear on the side opposite the youngest leaf primordium. A group of 8-9 cells subjacent to the CMZ represent the pith meristem subjacent to which are the longitudinal files of differentiating pith (Fig. 1). Mid stage: The tunica is 2-layered. Dome size increases and the depth of CMZ shows a slight decrease. The major portion of this zone is above the level of attachment of the youngest leaf primordium. The PZ shows about 3-4 cell layers on both flanks (Fig. 2). Maximal stage: Size of the apical dome shows a further increase, the increase in height being more. The tunica has two cell layers. The CMZ shows a further decrease in its depth. Periclines in cell layers underlying the outer tunica layer on the flank indicate the site for the next leaf primordium. The PZ is well developed with 3-5 regular cell files. The cells of PM occur in vertical files followed proximally by the differentiating pith (Fig. 3). Reprod ucti ve apex: During the flowering season most of the axillary buds develop into inflorescence apices. The inflorescence is a globose head and produces
Figs. 1-3. Median longitudinal sections of vegetative shoot apices at different plastochronic stages. Fig. 1. Minimal, X 500 Fig. 2. Mid, X 375 Fig. 3. Maximal, X 375 30 Flora, Bd. 174
470
A.
PILLA!
and K. C.
SHARMA
Figs. 4-7. Median longitudinal sections of reproductive apices. Fig. 4. Young inflorescence apex, X 315. Fig. 5. Inflorescence apex with bract and floret primordia at different developmental stages, X315. Fig. 6. Inflorescence apex with young bracts and axillant florets, X 90. Fig. 7. Floret apex, X 450.
bracts and axillant floral primordia acropetally (Fig. 5). The enlargement of the apex is followed by the establishment of a broad lightly chromophilic, large celled core covered by a multilayered mantle of densely chromophilic cells. The tunica, PZ as well as the CMZ are involved in the formation of the mantle layers, the major contribution being from the PZ. The mantle of the young inflorescence apex shows an axially located group of lightly stained cells which is not observed when bracts start developing (Fig. 4). The bract primordia are initiated when the inflorescence apex measures about 168 and 188 pm in height and diameter respectively. The cells in the inner mantle layers at the site of bract production are more densely stained than other mantle cells and start dividing in all planes. The outermost mantle layer cells divide by rapid anticlinal divisions. When the bract develops to a height of about 20 pm, the axillary fl~ret primordia also develop a mantle-core organization (Figs. 6, 7).
Shoot Apical Organization
471
D-DIAMETER
140
.-HEIGHT
3.., ~
0
120
100
0
-'
«
u 80 ii: <{
Lo..
0
60
Ul
z
0
iii 40
..,Z ~
0
20
0
ACACIA Fig. 8. Histogram depicting dimensions of vegetative shoot apices from monthly collections. (AZ - Axial zone; B -- Bract; BP - Bract primordium; CMZ - Central mother cell zone; F _ Floret; FP - Floret primordium; LP - Leaf primordium; M - Mantle; PE - Periclines; PM - Pith meristem; PZ - Peripheral zone; T - Tunica; T 1 , T2 - Tunica layers).
The floret primordia grow to a height of about 88 [tm and measure 80 [tm in diameter before the initiation of floral parts. The whole inflorescence apex is used up in flower formation and no residual meristem has been observed (Fig. 6). Only the mantle layers seem to be involved in the formation of bract and floret primordia. The latter develop a mantle-core configuration followed by the initiation of sepals, petals, stamens and carpels. The mantle shows 3-4 chromophilic cell layers and divisions in the mantle are responsible for the origin of floral parts (Fig. 7).
Discussion Analysis of the shoot apical meristem all round the year has helped consolidate inter-related aspects of shoot development. There are conflicting views about correlation between size and shape of the apex and growth habit. The data presented here support ROUFFA & GUNCKEL (1951) and fail to establish any correlation between shape and size of apex and growth habit of the plant.
In tree species there are many reports of a well marked cytohistological zonation in the shoot apex (GIFFOltD 1950; TOLBERT & JOHNSON (1966) and AGARWAL & PURl (1977» as well as reports denying the presence of zonation (RAMJI 1960; TUCKER (1962) and KAVATHEKAR (1976». The present study using anatomical stains failed to bring 30·
A. PILLAI and K. C. SHARMA
472
out differences in stainability between zones, whereas histochemical localization of RNA, total proteins and histones brought out a zonate distribution pattern (SHARMA et al. 1982). This supports the demarcation of the corpus into zones on the basis of cell net analysis. The gradual decrease in depth of theCMZ from minimal to the maximal stage of the plastochron indicates that cells from this zone become part of the PZ and PM during the plastochronic cycle. HAGEMANN (1960) reported that in Peperomia the flank meristem was renewed directly from cells of the apical initial zone at each plastochron. Measurements of apex size round the year bring out higher values during November to January and lowest values during seasons of active growth and elongation. This agrees with GIFFORD'S (1950) data on some woody ranales that maximum size may be correlated with active appandage formation rather than with shoot elongation. BONNAND (1959) in Nicotiana, CORSON & GIFFORD (1969) in Datura and GOYAL (1981) in Papaver species reported a lighter stained axial region in the reproductive apex. The early reproductive apex in Acacia also shows a similar zone though it does not persist in the older inflorescence apex producing bract and floret primordia. PLANTEFOL (1957) suggested that the anneau initial and meristeme d'attente may play different roles at flowering depending upon whether a terminal flower is produced or not. But data collected in this laboratory do not seem to support this. The floral apex in Papaver species producing a solitary flower, Sesamum with a cymose inflorescence (GOYAL 1981), Lantana which forms a flattened recemose inflorescence (GOYAL et al. 1981) and the present data on Acacia - all show a lighter stained axial region in the inflorescence and/or floral apex. Later in development, a uniform mantle region is formed over a central core involving the reorganization of all zones of the apex, rather than the stimulation of a previously inactive zone as suggested by adherents of the French school ofthought. In considerations ofthe proposed equivalence between the meristeme d'attente in the shoot and the quiescent centre in the root apex (SWAMY & KRISHNAMURTHY 1978), the observed differences lie probably in the very nature of the shoot apex in relation to the production of lateral organs and conversion to limited growth at flowering.
Acknowledgements The authors gratefully acknowledge the keen interest shown in the manuscript preparation by Prof. S. K. PILLAr. One of us (K.C.S.) is also thankful to the Head, Department of Botany for providing facilities.
References AGARWAL, R. M., & PURl, V. (1977): Ontogenetic studies in some important timber trees of India. I _ Shoot apex organization and leaf development in Dalber'gia SiS800. Phytomorphology 27: 296-302.
L. (variete white burley) en apex inflorescential. C.R. hebd. Seanc. Acad. Sci. Paris 248: 1209-1211. CORSON, G. E., & GIFFORD, E. M. Jr. (1969): Histochemical studies of the shoot apex of Datura stramonium during transition to flowering. Phytomorphology 19: 189-196.
1) BONNAND, J. (1959): Transformation de l'apex vegetatif de l"';1;cotiana. tabacum
Shoot Apical Organization
47~
CROSS, G. L. (1939): The structure and development of the apical meristem in the shoots of Taxodium distichum. Bull. Torrey bot. Club 66: 431-452. ENGLAND, W. H., & TOLBERT, R. J. (1964): A seasonal study of the vegetative shoot apex of Myriophyllum heterophyllum. Am. J. Bot. 51: 349-353. GIFFORD, E. M. Jr. (1943): The structure and deyelopment of the shoot apex of Ephedra altissima. DESF. Bull. Torrey bot. Club 70: 15-25. - (1950): The structure and development of the shoot apex in certain woody Ranales. Am. J.: Bot. 37: 595-611. GOYAL, S. C. (1981): Anatomical and morphological studies on some oil-yielding plants. Ph.D. thesis, Univ. Rajasthan, Jaipur. GOYAl" V., SHARMA, M., & PILLAI, A. (1981): Developmental studies on the shoot apex of Lantana camara L. In: Fourth Botanical Conference, Calicut University, Calicut. Abstract no. 59. 1) HAGEMANN, W. (1960): Kritische Untersuchungen liber die Organisation des Sprossscheiteis dikotyler Pflanzen. Osterr. Bot. Z. 107: 366-402. HARA, N. (1963): Structure of the shoot apex with special reference to Chimera formation. Gamma field symposia, Japan 12: 97-112 . •TOHANSEN, D. A. (1940): Plant microtechnquie. McGraw Hill Co., New York. KAVATHEKAR, K. Y. (1976): Anatomical studies on some Ranales. Ph.D. Thesis, Univ. Rajasthan, Jaipur. & PILLA I, A. (1980): Studies on the developmental anatomy of Ranales. VII. Shoot apical organisation in some members of Annonaceae. Flora 169: 245-253. PAOLILLO, D .•T. Jr., & GIFFORD, E. M .•Jr. (1961): Plastochronic changes and the concept of apical initials in Ephedra altissima. Am. J. Bot. 4S: 8- -16. PILLAI, A., & KAILASH (1982): Developmental anatomy of Albizia lebbek. I. Shoot Apex. Acta Bot. Indica 10: 79-S4.
-
& KAvA'rHEKAR, K. Y. (1975): Apical meristems in Nymphaea stellata WILLD. Proc. Indian Acad. Sci. SIB: 91-100. PILLAI, S. K., & CHACKO, B. (1978): Growth periodicity and structure of the shoot apex of Picea smithiana (WALL.) BOlSS. An anatomical and histochemical stUdy. Flora 167: 515-524. 1) PLANTEFOL, L. (1957): Sur deux notes relatives a l'ontogenie d'inflorescences. C. R. Acad. Sci. Paris 245: 503-607. -
RAMJI, M. V. (1960): The structure of the shoot apex and leaf initiation in Polyalthia longifolia. Proc. Indian Acad. Sci. 5IB: 227-241. ROUFFA, A. S., & GUNCKEL, J. E. (1951): A comparative study of vegetative shoot apices in the Rosaceae. Am. J. Bot. 3S: 301-307. SHARMA, K., SHARMA, M., & PILLAI, A. (1982): Histochemical analysis of zonation in .the shoot apex of Acacia nilotica. J. Indian Bot. Soc. Communicated. SMITH, C. A. (1963): Shoot apices in the family Moraceae with a seasonal study of Maclura pomifera (RAF.) SCHNEID. Bull. Torrey bot. Club 90: 237-25S. SWAMY, B. G. L., & KRISHNAMURTHY, K. V. (1978): Certain conceptual aspects of meristems. III. A model. Phytomorphology 28: 1-7. TOLBERT, R. J., & JOHANSEN, M. A. (1966): A survey of the vegetative shoot apices in the family Malvaceae. Am. J. Bot. 53: 961-970. TUCKER, S. C. (1962): Development and phyllotaxis of the vegetative axillary bud of Michelia fuscata. Am. J. Bot. 50: 661-66S. 1) Not seen in original
Received October 5, 1982 Authors' address: Dr. A. PILLAI and K. C. SHARMA, Department of Botany, University of Rajasthan, Jaipur - 302004, India.