摘要:

Regeneration inFucus vesiculosusL., both under natural conditions and in culture, has been studied histologically.Cut segments of vegetative tissue from matureFucusspecimens were cultured in seawater. Histological sections of this material were prepared at various intervals up to 8 months of culture to follow the development of adventitious branches from the wound surfaces. In both cultured segments and whole, naturally wounded plants, existing filament and cortical cells in the midrib region of wound surfaces differentiate a new epidermis. Several loci on this new epidermis undergo increased rates of periclinal division to produce structures which are morphologically very similar to normalFucusembryos and which ultimately acquire apical grooves and apical cells and become flattened in the manner of normal vegetative thallus branches. The significance of the wound-healing process and the formation of adventive embryos is discussed.

ISSN:0008-4026    

DOI:10.1139/b69-239

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In comparison with controls, 40-year-old loblolly pines (Pinus taedaL.) subjected to drought showed a marked increase in reducing sugars, nonreducing sugars, and total carbohydrates; and an approximately equivalent decrease in starch. The increase in sugars apparently was primarily the result of a decrease in growth rate and not hydrolysis of starch. Changes in the inner bark of trees stressed by continuous flooding followed the same basic pattern except that the marked increase in sugars occurred later, after severe stress had been established; stress probably was due to root failure. Drought and flooding had no effect on accumulation of amino N. Initially, synthesis of insoluble (protein) N was depressed but later the trend was reversed.

ISSN:0008-4026    

DOI:10.1139/b69-240

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Seeds of peas,Pisum sativumL. varieties Alaska and Early June, were soaked for 3 hours in 2.3 × 10−3 M2-chloroethylphosphonic acid (CEPA) or 3 × 10−5 Mgibberellic acid (GA3), sown in steamed or root rot soils, and grown to flowering stage at controlled soil temperatures with 14 hours per day of 32 000 lumens per square meter. CEPA delayed emergence and decreased survival in var. Alaska, but increased survival in var. Early June between 14 C and 18 C. GA3decreased survival in both varieties. Early emergence was followed by increased wilting. CEPA showed antigibberellin activity, in most instances counteracting the adverse effects of GA3.

ISSN:0008-4026    

DOI:10.1139/b69-241

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Evidence is presented suggesting that increased seed exudation is a major factor contributing to increased preemergence damping-off of cotton seedlings byRhizoctonia solaniat low temperatures.About seven and three times as much total amino acids and sugars were exuded at 18 and 24 °C, respectively, as at 30 °C, by germinating cotton seeds of equivalent physiological age. Sixteen amino acids and five sugars were exuded. Seed exudation is not related to rate of germination or to respiration.Accumulation of seed exudate at low temperatures was related to increased pathogenesis in vitro and in soil. This appeared to be becauseR. solanicompetitively used this exudate to increase its inoculum potential near the germinating seed, thereby becoming more virulent on the susceptible juvenile tissues of the seedling.

ISSN:0008-4026    

DOI:10.1139/b69-242

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Four pollen zones are present in a 360-cm core of sediment from Rice Lake, Becker County. The zones indicate a vegetation succession from mid-postglacial oak savanna to deciduous forest to pine-hardwood forest to an uppermost ragweed zone representing postsettlement forest disturbance. Seeds of wild rice occur in the upper meter of the core with abundant wild rice type pollen. The initial increase of wild rice type pollen is radiocarbon dated at 2450 ± 100 years ago. The ragweed pollen rise that dates land settlement about 75 years ago is radiocarbon dated at 590 ± 95 years ago. The difference is attributed to contamination by dead carbon, and when this error is subtracted from the older date, the corrected age for the spread of wild rice across the lake is 1935 ± 100 radiocarbon years ago.An extensive stand of wild rice at this lake predates by 1000 years prehistoric cultures known to have used wild rice in Minnesota.The spread of wild rice is probably due to either climatic change and associated changes in water quality or to shallowing of the lake by sedimentation, or both factors.

ISSN:0008-4026    

DOI:10.1139/b69-243

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Concentrated water extracts from foliage and from roots of sweet-fern were used as moistening media in laboratory tests on germination and survival of red pine. Neither inhibited germination, but both affected survival adversely. In tests simulating field conditions germination, survival, and growth were judged to be more closely related to moisture than to the presence of sweet-fern.

ISSN:0008-4026    

DOI:10.1139/b69-244

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The uptake of phenylalanine during imbibition by seeds of the garden pea (Pisum sativum, var. Alaska) was studied using 1-14C-L-phenylalanine. The distribution of the radioactivity within the seed was observed using a radioautographic procedure. The results indicate that phenylalanine, while presumably diffusing passively with water, nevertheless exhibited some independence of movement. This conclusion is based on (a) the decline in counts per milliliter of the imbibition medium, and (b) the low activity observed in the axis tissue, an area which becomes hydrated early in the imbibition process. Entry of phenylalanine into the seeds appears to be entirely through the micropyle, with rapid diffusion across the cavity occupied by the shoot–root axis and between the seed coat and cotyledon, followed by diffusion inwards through the cotyledon tissue.

ISSN:0008-4026    

DOI:10.1139/b69-245

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Controlled pollinations were made within and between blue spruce (Picea pungensEngelm.) and white spruce (Picea glauca(Moench) Voss) in 1967 and 1968. Interspecific hybrids were obtained and verified by comparative measurements of several traits. The cross was successful when either species was used as the female parent. Hybrid seed germinated more rapidly than that of either species and hybrid seedlings showed some heterosis for early growth. Also, hybrid seedlings had needles intermediate between, and significantly different from, the parental seedlings. Growth form of the hybrid was quite variable compared with that of either species. Further evidence for the successful crossing of blue spruce and white spruce was provided by biochemical analyses of monoterpene compounds in the parents and progeny.

ISSN:0008-4026    

DOI:10.1139/b69-246

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The distribution of photoassimilated carbon-14 in young plantation trees was studied 6 or 10 days after supplying14CO2for a day to a single branch in the second, third, or fourth whorl. Both apical and cambial growth occurred during the interval, and apical growth throughout the trees was measured. Elongating terminals and products of cambial growth in the fed branch were highly labeled. In all trees some14C was exported to the adjacent side of the tree. Movement in the trunk was bidirectional, but the position of the donor branch determined the direction of major transport. Only from whorl 2 was it upward; from whorl 3 or 4 it was downward. In both directions activity decreased with distance from the base of the donor branch, and the leader did not accumulate more, per unit weight, than the intervening internodes. Some14C entered branches arising in the path of transport.Radioactivity was concentrated only in regions of growth, whether apical or cambial. Most of the14C was in ethanol-insoluble compounds, largely in cell wall constituents. Autoradiographs of stem sections confirmed that14C was deposited in currently developing tracheids of secondary xylem during most of the 10-day growth period. The ratio of activity in lignin to that in cellulose was inversely related to the total14C in the cell wall constituents.

ISSN:0008-4026    

DOI:10.1139/b69-247

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Histological comparisons were made of immune, intermediate, and susceptible reactions ofLinum usitatissimumtoMelampsora liniat intervals after inoculation. All reactions were quite similar for the first 36–48 h. Immunity was correlated with length and number of hyphae per infection site as well as the number of haustoria per infection site. Haustorial size was not related to host reaction. The number of collapsed host cells and the area of starch accumulation were useful for comparison of widely divergent, but not of similar reaction types. Tissue transplant studies showed that the mycelium was killed, rather than retarded in the immune reaction.

ISSN:0008-4026    

DOI:10.1139/b69-248

出版商:NRC Research Press    

年代:1969

数据来源: NRC