摘要:

The subepidermal cell layer was the site of origin of the first periderm in the hypocotyl and internodes ofFraxinuspennsylvanicaandAilanthusaltissima. In the hypocotyl ofRobiniapsendoacacia, the first periderm arose in cortical cells near the phloem; in the internodes it originated in the subepidermal, second, or third cortical cell layer. The outermost cell layer of the pericycle gave rise to the first periderm in the hypocotyl ofPinusresinosa. In all four species, periderm appeared first near the base of the hypocotyl and developed acropetally. InA.altissimaandR.pseudoaeacia, phellem mother cells were cut off by the phellogen. These subsequently divided to produce phellem cells. InF.pennsylvanicaandP.resinosa, phellem cells were produced directly from the phellogen.

ISSN:0045-5067    

DOI:10.1139/x72-024

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Three-day-old seedlings ofFraxinuspennsylvanicawere transferred to soil undergoing periodic drying or continuous subirrigation. Seedlings were harvested after 24 days. Germinating seeds ofF.pennsylvanicawere exposed to 1, 10, 20, or 30% polyethylene glycol (PEG) for 35 days and 1-day-old seedlings were exposed to 1, 10, or 20% PEG for 35 days. Seedlings grown on drying cycles or in 20% PEG had smaller periderm and xylem increments than seedlings grown in continuously subirrigated soil or 1 or 10% PEG, respectively. Xylem increment was affected more than periderm increment by water deficits. Germinating seeds exposed to 10 or 20% PEG did not develop periderm or secondary xylem and did not expand foliage. Thirty per cent PEG caused desiccation and death of germinating seeds. Seeds exposed to 1% PEG germinated and developed normally. When water deficits occurred during germination the foliage failed to expand and periderm formation was thereby prevented. Water deficits subsequent to seed germination reduced periderm increment less than they reduced xylem increment, indicating difference in physiological controls.

ISSN:0045-5067    

DOI:10.1139/x72-025

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

In May 1969 the weed vegetation on one plot in a 7-year-old red pine (PinusresinosaAit.) plantation was killed with herbicides. The site was a glacial outwash plain in Adams County, Wisconsin. Tree diameter growth was 30% greater on the plot without weeds in the summer of 1969, and 8% greater during the first half of the 1970 growing season. Based on relative height growth of the previous year, weed removal increased height growth by 13% in 1970. Growth differences were attributed to increased available water resulting from weed removal because needle water potentials were lower and stomatal resistances much higher in the presence of weeds during dry conditions in the plantation.

ISSN:0045-5067    

DOI:10.1139/x72-026

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

This paper presents mathematical equations describing the relationships between the amount of stemflow per canopy layer per storm and the amount of gross rain per storm for four different canopy layers in a multi-storied forest community. The curves representing the relationships were curvilinear; for three of the canopy layers stemflow per storm increased at an increasing rate as gross rain per storm increased, approaching a constant rate of increase. Numerical values of the equation coefficients varied with canopy level in the forest stand profile and with variations in vegetal structure within the forest community. The lowest canopy in the vegetal profile, a fern canopy, had the most marked effect on rainfall redistribution.

ISSN:0045-5067    

DOI:10.1139/x72-027

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

To facilitate foliage sampling in a physiological study, a portable, inexpensive, and easily constructable tree platform was designed that minimized damage to the tree while providing a solid work base. The design and construction of the platform is described.

ISSN:0045-5067    

DOI:10.1139/x72-028

出版商:NRC Research Press    

年代:1972

数据来源: NRC