摘要:

Chromosome numbers are reported from 67 populations of 36 taxa, mostly inPhoradendron.The basic number is 14 inPhoradendronand probably also inArceuthobium.The 4 species ofStruthanthusfor which chromosome numbers are recorded suggest that the basic number is 8. Numbers ofn= 8 andn= 10 have been reported forPsittacanthus.InPhoradendronthe 22 taxa examined are all diploid, although 1 instance of polyploidy was discovered. Objects interpreted as supernumerary chromosomes were discovered in a number of species ofPhoradendron;no evidence of sex chromosomes previously reported inPhoradendronwas observed. The Loranthaceae have chromosomes comparable in size to the largest in the plant kingdom.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06592.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Aspects of anatomical development were correlated with internodal growth in tomato plants, variety ‘Yellow Plum,’ grown for more than 3 months. Internodal length was measured weekly in control plants and those harvested for anatomical study. Gross structure indicated progressive development with increasing age. Primary xylem and phloem first mature in distinct strands and the strands are joined laterally by procambium to form a continuous vascular cylinder. Primary phloem occurs on the outer periphery of the procambium between the early‐formed vascular strands. Successive periclinal divisions in the procambium during internode elongation give rise to pronounced radial seriations of the cells. Procambial derivatives are included in the cylinder of thick‐walled, lignified vascular cells that become prominent after elongation ceases. Secondary xylem is of greater radial width in the stem sectors which include protoxylem. During early secondary growth, vessels develop in the secondary xylem only in these sectors. Nucleate fibers and rays constitute the remainder of the secondary xylem. The rays exhibit an organization noted in other plants of reduced growth habit. Some of these interpretations do not agree with those described for tomato in earlier studies, and they are discussed in relation to pertinent aspects of development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06593.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Excised internodes and 2‐mm‐thick transverse stem segments ofColeus blumeiwere incubated 7 days on media containing 2% sucrose, 1% agar, and various growth substances. Wound‐vessel members differentiated in the 2‐mm‐thick tissue slices incubated on medium containing no exogenous auxin (control). Compared to control slices, the addition to the medium of either IAA (50 or 5 ppm), 2, 4‐D (10, 1, or 0.1 ppm), TIBA (50, 5, or 0.5 ppm), or kinetin (50, 5, 0.5 or 0.05 ppm) inhibited wound‐vessel differentiation. Simultaneous treatment of tissue slices with IAA and kinetin inhibited wound‐vessel differentiation, as did the incubation of tissue slices on medium containing no sucrose. Low concentrations of IAA (0.05 ppm) or 2, 4‐D (0.01 ppm) resulted in over a 100% increase in the numbers of wound‐vessel members differentiated. These results are interpreted as indicating auxin synthesis by the tissue slices and the participation of auxin as a limiting factor in xylogenesis. The inhibition of wound‐vessel differentiation by relatively high concentrations of 2,4‐D, TIBA, or kinetin is interpreted as a reflection of the inhibition of polar auxin transport by these substances, and an indication that polar auxin transport enhances xylogenesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06594.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

The 2 types of fruit (aerial and subterranean) borne by the dwarf desert annualGymnarrhena micranthawere compared with regard to their responses to factors affecting their formation, dispersal, germination and seedling mortality. The 2 types of fruit differed markedly in several respects. In comparison with the subterranean fruits, the aerial ones are much smaller and more numerous, but the formation of the inflorescence in which they develop is more dependent on a favorable supply of soil moisture. The aerial fruits are dispersed by wind, after becoming detached by a complex series of hygroscopic movements which involve several organs and tissues, while the subterranean fruits never leave the dead parent plant, germinating right through its tissues. Germination of the subterranean fruits starts after a shorter incubation period and is less temperature‐dependent in both light and dark. Light stimulated germination of both types of fruit, increasing their germination rates and final percentages, but not affecting the duration of the incubation period. In the subterranean fruits, the rate of germination was equally stimulated by light over the entire temperature range, with a well‐defined optimum at 15 C in both light and dark. In the aerial fruits, the same optimum was found only in the light, rates in darkness increasing with decreasing temperatures. In the aerial fruits, alternations of light and dark were more favorable to germination than either continuous light or dark, the full effect being obtained with a single 8‐hr or 16‐hr light period, provided it was preceded by 16 or 8 hr of darkness, respectively. Similar reactions to combinations of light and dark were not observed in the subterranean fruits. Seedlings developing from the subterranean fruits were much larger, but grew at a relatively much slower rate than those from aerial fruits. The former were distinctly more tolerant of unfavorable soil‐moisture regimes, such as low moisture supply and drought. It was concluded that the 2 types of fruit serve 2 distinct functions in the biology of the plant. The aerial fruits are adapted to the function of increasing the distribution of the species within suitable habitats, while the subterranean fruits are adapted to increasing the probability of the survival of the species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06595.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

A study of the carpel in 27 species ofPrunushas shown certain notable structural relationships associated with the extent of closure of the carpellary margins. These relationships involve the degree of fusion of the 2 integuments, the number of vegetative bundles in the base of the carpel, the extent of fusion of the ovular bundles with one another and with the wing bundles, the relative size of the ovular bundles, and the relative development of the central vascular plexus. The comparative evidence strongly supports a primitively separate state of ovular and vegetative bundles. The significance of this finding is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06596.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Three inhibitors of stem elongation, Amo, CCC, and Phosfon, inhibit cell division and expansion in tissues cultured in vitro. However, contrary to the case in intact plants, gibberellic acid does not prevent the retardant‐induced inhibition in vitro. Supplementary auxin is also without effect in preventing the inhibition. Thus, the effect of the retardants cannot be simply that of inhibiting gibberellin or auxin synthesis. With respect to growth, carrot, chrysanthemum, and geranium tissues are equally sensitive to all 3 retardants, whereas tobacco tissues are considerably more resistant to Amo and apparently unaffected by CCC.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06597.x

出版商:Wiley    

年代:1964

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06598.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Two diploid taxa,Grindelia proceraandG. camporum,and 3 tetraploid ones,G. camporum, G. hirsutula,andG. stricta,have been studied to ascertain their interrelationships. Meiosis in diploid parental strains was regular, the common chromosome configuration being 5 rod bivalents and 1 ring bivalent. The average chiasmata frequency per chromosome was 0.60. Pollen fertility was about 90% in all strains examined. Diploid interspecific hybrids had normal meiosis with an average chiasmata frequency of 0.56 per chromosome. No heterozygosity for inversions or interchanges was detected, and pollen fertility was above 85%. Meiosis in parental tetraploid strains was characterized by the presence of quadrivalents in addition to a complementary number of bivalents. The average chiasmata frequency per chromosome was 0.59 and pollen fertility was generally about 80%. Tetraploid interspecific hybrids also had quadrivalents, normal meiosis, and high pollen fertility. Close genetic relationships between the diploids and between the tetraploids are indicated, and geographical, ecological, and seasonal barriers to gene exchange exist. Attempts to obtain hybrids between diploids and tetraploids were successful in a few cases. The hybrids were tetraploid and had normal meiosis and fertility similar to parental and F1tetraploids. Their origin was by the union of unreduced gametes of the diploid female parent and normal pollen from the tetraploid parent. On the basis of chromosome homology, normal meiosis, plus high fertility exhibited in the diploid, tetraploid, and diploid X tetraploid interspecific hybrids, these species ofGrindeliaare considered to be a part of an autopolyploid complex. Gene exchange between diploids and diploids, tetraploids and tetraploids, and diploids and tetraploids is possible. TetraploidG. camporummay have originated by hybridization betweenG. proceraand diploidG. camporumwith subsequent doubling of chromosomes and selection for the combined characteristics of the diploids.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06599.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

A new species ofSpongiochloris, S.typica,was isolated from a Connecticut soil. It can be distinguished from other species by the presence of many pyrenoids; by the cell size of light‐grown cells (up to 80μ), usually with thin walls; and by the vacuolate older cells. Zoospores present favorable material for observation of withdrawal of flagella upon quiescence. The organism was reintroduced into sterile soil, the soil was then air‐dried, and the viability of the organism in soil was measured during 1 year. Each month, a 0.5‐g sample of soil was heated at 100 C for 1 hr prior to incubation in basal medium; a control sample was incubated, along with the treated soil, in continuous illumination. By means of 10‐fold dilutions of such cultures, it was determined that more than 10,000 cells per 0.5 g of soil survived heat pretreatment and more than 100,000 cells per 0.5 g were viable in the desiccated soil after 1 year.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06600.x

出版商:Wiley    

年代:1964

数据来源: WILEY

摘要:

Growth of theLilium longiflorumpollen tube in vitro is restricted to a zone extending back 3–5 μ from the tip. Electron micrographs of cross and longitudinal thin sections ofL. longiflorumandL. regalepollen tubes reveal that the cytoplasm of the nongrowing region of the tube contains an abundance of mitochondria, amyloplasts, Golgi bodies, endoplasmic reticulum, lipid bodies, and vesicles. In contrast, the growing tip is characterized by an abundance of vesicles and an absence of other cytoplasmic elements. The vesicles appear to be of 2 types. One is spherical, about 0.1 μ in diameter, stains strongly with phosphotungstic acid, apparently arises from the Golgi apparatus and appears to contribute to tube wall and plasmalemma formation. The other type is irregular in shape, 0.01‐0.05 μ in diameter, stains strongly with lead hydroxide, and is of unknown origin and function. Cytochemical analysis indicates that the tips ofL. longiflorumpollen tubes are singularly rich in ribonucleic acid, protein, and carbohydrate. These findings are discussed in relation to tube growth.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1964.tb06601.x

出版商:Wiley    

年代:1964

数据来源: WILEY