摘要:

Not more than half the seeds borne by maize plants of the W23 inbred strain, homozygous for a mutant gene termed “indeterminate gametophyte” (ig), develop normally. The remainder exhibit polyembryony (6 %), heterofertilization (7 %), elevated ploidy level of the endosperm (45 %), or other less frequent anomalies. Theigeffects were identified and characterized by chromosome counts and genetic tests. Twins were regularly found to be diploid and concordant for heterozygous marker genes introduced maternally. When the marker genes were introduced paternally, twins frequently were non‐concordant, or the embryo and endosperm phenotypes did not correspond. The proportion of the various types and the absence of conjoined embryos indicated that, although identical in their maternal inheritance, the twins were regularly dizygotic. Those twins identical in paternal inheritance probably originate from the fertilization of two genetically identical eggs by the two sperm of one male gametophyte. Whenig igcompared to normal diploid plants were pollinated by tetraploids, the proportion of plump seed formed was markedly increased. Evidently this result is the consequence of elevation of the endosperm ploidy level by theiggene. Theiggene thus appears to interfere with differentiation of the components of the female gametophyte so that the number of eggs and polar nuclei, instead of being one and two, is indeterminate.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09938.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Rooted stems of three aquatic species were cultured in a two‐compartment apparatus which allowed the upper and lower portions of the stem to be kept in different nutrient solutions. P32was supplied to either the upper or lower compartment. At the end of a 10‐day growth period, the specific activity of phosphate was determined in axillary shoots which developed during the course of the experiment from buds in the upper compartment. The results indicated that most of the phosphate in these shoots was not absorbed from the ambient medium but was derived from the rooted stem base in the lower compartment (over 90 % inMyriophyllum brasiliense, 59 % inM. spicatum, and 74 % inElodea densa). These results give a very different but probably more accurate picture of phosphate absorption in rooted aquatic vascular plants than short‐term experiments, in which phosphate is readily taken up from the ambient medium by leaves ofM. spicatumandE. densa. InM. brasiliensethe amount of phosphate translocated is related to the mass of roots present. Evidence is presented that normal growth of axillary shoots occurs even when all mineral ions have to be obtained by translocation from the lower compartment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09939.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Style abscission was studied in detail in citrons (Citrus medicaL.) and other citrus varieties. The course of style abscission was followed under orchard conditions and also in an “explant” system consisting of pistils implanted in an agar‐sucrose medium and maintained at 25 C in a humid chamber. Morphological and anatomical observations carried out with the explant system revealed a prominent swelling of cell layers proximal to the separation layer prior to abscission. Tests with explants from flowers of different developmental stages showed that before the end of anthesis only the ovaries are capable of performing abscission while style abscission is possible only at a later stage, presumably after fertilization had occurred. Ethylene was able to induce ovary abscission at later stages but could not induce earlier style abscission. Picloram (4, amino‐3,5,6‐trichloropicolinic acid) increased the percentage of style persistence in citron varieties which naturally tend to retain their styles. Picloram also induced style persistence in Valencia oranges and Eureka lemons, which naturally show 100 % style abscission. Hormonal determinations showed that the style had higher levels of auxin than the ovary but also higher levels of inhibitors, which increased towards the time of style abscission.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09940.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Laboratory‐germinated seedlings from Connecticut, New Jersey, Illinois, Tennessee, Texas, and Florida were compared under four photoperiod temperature programs. Under each controlled condition, seedlings of northernmost provenances demonstrated least stem elongation and earliest dormancy. Greatest sensitivity to cool temperatures and short photoperiods was demonstrated by northernmost provenances. At warm temperatures, dormant bud formation was controlled by photoperiod in all populations tested except those from Texas and Florida. The reported differences among populations reflect the effects of natural selection upon differentLiquidambarpopulations, insuring survival of the species in various habitats.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09941.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

A new genus and species of the Protosteliida (Mycetozoa),Ceratiomyxella tahitiensis, was isolated from dead plant material—var.tahitiensisfrom Tahiti and var.neotropicalisfrom Brazil and Colombia. The sporocarps have deciduous spores borne singly on slender hollow stalks; zoocysts with anteriorly flagellate planonts are produced. The trophic stage is comprised of uninucleate to plurinucleate amoeboid cells and reticulate plasmodia; the uninucleate cells become flagellate in water. The prespore cells and spores are plurinucleate. Sexuality has not been demonstrated. Var.tahitiensishas globose spores and produces its zoocysts just after spore germination, whereas var.neotropicalishas subglobose spores and forms zoocysts later in the life cycle. The species is thought to show phylogenetic relationships withCeratiomyxa, which was recently transferred to the Protosteliida by Olive.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09942.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Chromosome numbers of n = 8, 12, and 16 were determined for 11 populations ofClaytonia lanceolataoccurring in the southwestern Rocky Mountains of Utah. No evidence of the wide infra‐populational variation of chromosome numbers known in the related eastern species,C. virginica, was observed. The chromosome numbers inC. lanceolataprobably evolved from a base number of x = 8. Diploids(n = 8) apparently produced tetraploids (n = 16) of putative autoploid origin. Pairing relationships, including the presence of univalents, bivalents, and trivalents, suggest the chromosome numbers of n = 12 are triploids derived from natural hybridization between diploids and tetraploids. Higher chromosome numbers previously reported inC. lanceolatafrom Colorado, and presumably based on x = 12, can be explained by subsequent polyploid increases in the triploids. The diploid and tetraploid populations analyzed in this study occupy different ecological habitats. The diploids occur at lower elevations along the foothills, whereas the tetraploids are restricted to higher montane and sub‐alpine elevations. The triploids were discovered at intermediate elevations.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09943.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

A study was conducted to determine germination response to temperature and salinity and seedling response to salinity by three height forms of the salt marsh grassSpartina alternifloraLoisel. Germination tests showed that seeds cannot withstand drying at moderate temperature, as viability was lost within 40 days in seeds stored dry at 72 F. Cold storage at 43 F is adequate to prevent desiccation up to 40 days, but after 8 months viability is lost. Viability is retained at least 8 months when seeds are stored in sea water at 43 F. Germination response was good in a 65–95 F alternating diurnal thermoperiod but was poor in a 72 F constant thermoperiod. Germination response to salinity was an inverse curvilinear relationship with germination inhibition at high salinities apparently due to osmotic effects. The maximum tolerance limit for germination lies between 6 and 8 % NaCl. Seeds from short, medium, and tall plants responded similarly in storage and temperature studies. However, in salinity studies, seeds of the Ocracoke Island short form and the Oak Island tall form performed best. A logarithmic curve best described seedling growth response to various NaCl levels. Growth response as measured by seedling dry weight was best in 0.5 % NaCl solution. Seedlings grew taller in both 0.5 and 1.0 % NaCl than in 0 % NaCl. No significant difference in seedling growth response due to height form of the parent plant was detected. Thus, on the basis of germination and seedling responses, the height forms ofS. alterniflorain North Carolina salt marshes are best described as ecophenes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09944.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

The cytology of ascus development inNectria cinnabarinawas investigated with the orceinsmear technique, from crozier formation to ascospore maturation. At prophase I synapsis occurs while the chromosomes are still contracted, and the nucleus passes through dictyotene, a diffuse stage rarely seen in plants. A haploid complement of five chromosomes has been precisely determined. The first two divisions in the ascus constitute meiosis, and the third (mitotic) is followed by ascospore delimitation. A fourth division takes place in the ascospore, which is subsequently divided by a septum into two uninucleate cells. Of all species ofNectriathus far investigatedN. cinnabarinais the only species in which additional nuclear divisions in the ascus do occur, accounting for the multinucleate condition in the ascospore cells. The bearing that this distinctive nuclear condition has on phylogeny and evolution in the Hypocreales is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09945.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Seedlings ofIpomoea purpureawere grown in aseptic culture in order to investigate more directly than had been possible in pot culture the effect of carbohydrate and protein nutrition on heteroblastic development which in this species involves a change from entire juvenile to lobed adult leaves. The effect of sugars was to accelerate the development of the adult leaf form while casein hydrolysate retarded it. The growth retardants, AMO‐1618 and CCC, also promoted the formation of the adult leaf. These results are discussed in the light of current views on the factors controlling heteroblastic development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09946.x

出版商:Wiley    

年代:1971

数据来源: WILEY

摘要:

Cytological comparisons were made of triploid and 3x – 1 plants ofGossypium hirsutum(haplo 17 and 18) XG. aridum, G. armourianum, G. harknessii, andG. raimondii. Tests and observations led to these conclusions: (1) Chromosome conjugation varied significantly from plant to plant and date to date within plants. (2) The D genome chromosomes ofG. hirsutumare closer in homology toG. raimondiithan to the other species tested. (3) The chromosomes ofG. aridum, have closer homology to the A genome ofG. hirsutumthan do the chromosomes of the other D species tested. (4) The D genome ofG. hirsutumhas a small translocation as compared to the genomes of the four D species studied.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1971.tb09947.x

出版商:Wiley    

年代:1971

数据来源: WILEY