摘要:

The leaf plastochron index (LPI) was used to interpret the anatomical changes during leaf ontogeny in the developing leaf zone of young cottonwood trees and to relate leaf anatomical structure to physiological function. The lamina tip matured precociously with respect to both structure and function. Below the lamina tip the intercellular spaces, stomates, and minor veins matured basipetally, while the major veins developed acropetally. Ontogenetically, maturation progressed from LPI –1.0, which was anatomically immature except for its lamina tip, to the first fully expanded leaf at LPI 6.0, which was anatomically mature. Physiological maturity also occurred at LPI 6.0, thus signifying a transition with respect to both structure and function. By evaluating the anatomical observations in conjunction with physiological data collected at comparable LPI's in other experiments, it could be demonstrated that anatomical development was a limiting factor in photosynthesis and translocation of assimilates.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10217.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Anatomical analysis of wavy‐grained xylem samples ofFraxinus, Acer, andBetulareveals a strong underlying pattern of orientational domains within the cambium. Domains are local areas in the cambium within which the orientation of pseudotransverse divisions of fusiform initial cells is predominately unidirectional rather than random. The orientation of ray splitting and ray uniting also tends to be unidirectional within domains. Because their boundaries migrate with time, domains are not fixed in shape or position. A specific group of initial cells may first be located in the interior of a domain, later near a boundary, and still later in another domain of opposite orientational prevalence. Domain patterns and their movements were delineated by classifying and mapping ray splitting and uniting events in temporal series of tangential sections of terminal late xylem. The domain patterns move slowly upward, preceding the similarly outlined, but noncoincident, grain pattern. A wavy grain pattern can be interpreted as being the result of a domain pattern of similar geometry. The efficacy of a domain pattern in eliciting a grain pattern is probably indirectly dependent upon the frequency of occurrence of pseudotransverse divisions and of ray splitting and uniting. The frequency is low in cambium producing straight‐grained wood. Evidence of 10‐fold and greater increases in frequency of ray splitting and uniting was found in straight‐grained to wavy‐grained transitional xylem.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10218.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The development of a “palmelloid” phase was studied in an adventive growth of a species of the blue‐green algaAnabaenasp. and in culture of the same strain. The primary change from its characteristic filamentous structure was the separation of the cells from one another. This was accompanied by the excessive production of capsular slime in which the separated cells were arranged at random. Associated with this were a gross change in cytology and a change in shape of cell from spheroidal to enlarged ellipsoidal. Fresh culturing of palmelloid cells resulted in the resumption of the typical filamentous growth, which in time reverted to the palmelloid phase.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10219.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Experimental pollination studies indicate that probing into the corolla tube by insects is a requirement for autogamous reproduction inPhyla incisa. Insect‐mediated self‐fertilization combines the anthecology of allogamous reproduction with the genetic consequences of autogamy.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10220.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Movement of IAA in spider flower (Cleome hasslerianaChod.) stamen filaments was studied by placing 2‐mm sections horizontally between donor agar blocks containing14C‐labeled IAA and plain agar receiver blocks and measuring radioactivity in the donor and receiver blocks and filament sections by scintillation counting after the desired transport time. Movement was strictly polar and basipetal at all stages of floral development, except in open flowers just before stamen abscission when the amounts moving acropetally and basipetally were equal. The amount of IAA moved depended upon the stage of development. As buds aged more IAA was moved, until the buds opened and the stamen filaments reached maximum elongation; then the amount of IAA moving basipetally dropped drastically. There was an insignificant amount of acropetal IAA movement except just before stamen abscission. This change in IAA movement is not due to a change in filament diameter. In time‐course studies the amount of IAA moved basipetally increased with time up to 5 hr and then declined slightly. The amount of radioactivity retained by sections increased until 8 hr. The amount of IAA moved in tip sections was less than that in mid or base sections; however, this can be partially explained by differences in uptake area of these sections. The relationship of these results to the hypothesis that changes in IAA movement are important in the control of stamen filament elongation and abscission is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10221.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Leaf oils fromJuniperus occidentalis, J. osteosperma, andJ. califomicawere analyzed qualitatively and quantitatively for characteristic chemical composition. Seasonal, diurnal, and local microcline variation was quantified. Neither microcline nor seasonal variation appeared to have a significant effect on the leaf oil composition, although some variation was observed. A definite trend toward diurnal cycling was detected and tentatively linked to air temperature fluctuation from dawn to dark.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10222.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The vascular transition region ofHelianthus annuusL. may exhibit either a unilateral or a bilateral differentiation of primary phloem groups. The unilateral type of transition has been previously described but the bilateral type with its two variations is described here for the first time. The three patterns of transition are compared, and the significance of the variability of transition regions is discussed in terms of basic transition types and phylogenetic importance.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10223.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

Macrocyst germination was demonstrated in the five species of the Dictyosteliaceae known to produce these structures. The morphological changes that occurred during germination appeared to be identical in all of the strains examined, showing the following stages: (1) swelling of the dark, contracted content of the dormant cysts, (2) gradual loss of color and reappearance of cells within what previously appeared as a homogeneous protoplasmic mass, and (3) rupture of the heavy cellulosic cyst wall to liberate the myxamoebae. The age of the macrocyst appeared to be the most critical factor in determining whether or not germination would occur, since the cysts in many of the strains needed to age for several weeks or months before germination could be demonstrated. InDictyostelium mucoroidesstrain DM‐7, upon which the current study was centered, light was necessary to stimulate germination of young macrocysts—a requirement that gradually diminished as the cysts aged. The rate of germination and the temperature permitting germination were also age dependent: older macrocysts germinated more rapidly and at considerably higher temperatures than did young cysts. Although light was not essential for germination in every strain, the results obtained with strain DM‐7 seem to be generally applicable to the germination process.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10224.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

In liquid culture stem tissue of Paul's Scarlet rose produces a suspension containing cell aggregates of extremely variable dimensions. There is, however, a definite pattern of change in the degree of cell aggregation over time. During the period of most rapid cell division large aggregates form as the result of a minimal separation of the proliferating cells. As the rate of cell division slows, the average number of cells per aggregate decreases. The dissociation of cell aggregates continues at a uniform rate after cell division has stopped. Cell separation is inhibited at low (0.1 mg/1) auxin (NAA) concentrations and by substitution of sucrose for glucose in the culture medium. Cell separation is delayed (but not greatly inhibited) by kinetin. The presence of casein hydrolysate prevents the formation of the large cell aggregates normally occurring in the early stages of the culture cycle. A variant strain which shows a much higher degree of cell separation has been isolated from stock callus tissue grown on solid medium.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10225.x

出版商:Wiley    

年代:1973

数据来源: WILEY

摘要:

The incidence ofTridens oklahomensisFeath. withT. flavus(L.) Hitchc. andT. strictus(Nutt.) Nash together with its morphological intermediacy between the latter two species suggests a hybrid origin. Field and laboratory studies conducted over several years provide substantial evidence of an interspecific cross.Tridens oklahomensisappears in generally disturbed habitats, such as roadsides and cleared areas, where the adventive (for this region)T. strictusoccurs as overlapping populations with the ubiquitousT. flavus. At no time has the supposed hybrid been recorded solely with one or the other of the two species. On a moisture gradient,T. strictusis found mainly in swales and ditches whileT. flavusoccurs on the drier and more general upland. The hybrid occurs toward the moist end of gradient, nearT. strictus. On this basis it is reasoned that the latter is the pistillate parent. The hybrid is sterile and has no vegetative means of spreading. Under these conditions its presence is limited to chance fertilization in those situations whereT. strictushas invaded the range of the more widespreadT. flavus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1973.tb10226.x

出版商:Wiley    

年代:1973

数据来源: WILEY