William R. Chaney

THE PLASTOCHRON INDEX: A REVIEW AFTER TWO DECADES OF USE1

The plastochron index provides a morphological time scale which has proved more reliable than chronological age in studies relating morphological and physiological development of a whole plant or plant organ. Since its inception in 1957, the index has been utilized in a variety of investigations from leaf ontogeny in cottonwood trees to rhizoid cluster initiation in algae. The plastochron index has been extensively used in studies involving source and sink relationships, leaf anatomy, cell differentiation, and primary vascularization. It has been used in investigations of hormonal regulation of plant growth and in studies of the effects of various environmental factors on developmental processes in crops. This paper reviews some of the literature from 1957 to present concerning the development and use of the plastochron index.

Concurrent establishment of ground cover and hardwood trees on reclaimed mined land and unmined reference sites

Abstract A reclaimed mined site and an unmined reference site were compared to assess the effectiveness of reclaiming land according to United States Public Law 95-87, The Surface Mining Control and Reclamation Act of 1977, for forest land use. Red oak (Quercus rubra L.) and black walnut (Juglans nigra L.) seedlings were planted concurrently with K-31 fescue (Festuca arundinacea Schreb.) and red clover (Trifolium pratense L.), and maintained under the same levels of management on mined and unmined sites in Sullivan County, Indiana. Soil chemical and physical properties were evaluated, and ground-cover productivity was assessed for 4 years. Survival and growth of bareroot and container seedlings as influenced by chemical control of competing ground cover was followed for 7 years. After liming and fertilization, mine soil physical properties rather than chemical properties were apparent factors affecting survival of tree seedlings and productivity of both tree species and ground-cover vegetation. Survival percentage of black walnut and red oak seedlings on the mine site was adequate to meet the 450 trees acre−1 (≈ 1112 trees ha−1) stocking level specified by current laws only when ground cover vegetation was controlled. Survival and height growth of both tree species was greater on the reference site than on the mine site, especially when ground-cover vegetation was controlled. The poorer growth on the mine site was due to severe stem dieback on plots with no ground-cover control. The results show the importance of controlling the competing ground-cover vegetation during seedling establishment on reclaimed mine soils, particularly during the first 4 years following outplanting.

ORGANIC MATTER INFLUENCES PHYTOTOXICITY OF CADMIUM TO SOYBEANS

SummarySoybeans (Glycine max L. var. Williams) were grown for six weeks in a greenhouse in quartz sand containing 0, 0.5, 1, 2, 4 or 8% (w/w) sterilized peat moss. The cation exchange capacities of the organic matter-sand (OM-S) mixtures ranged from 0.01 to 8.88 meq/100 g dry weight. Imposed on each OM-S mixture was a treatment of 0, 1.25, 2.5, 5.0, 10.0 or 20.0 ppm Cd applied as CdCl2·21/2H2O. Height growth was measured weekly and at harvest plants were separated into leaves, stems and roots for dry weight and tissue Cd determinations. For plants grown in sand alone, height growth and dry matter accumulation in all tissues were reduced and Cd content was increased. These effects were correlated with increasing Cd concentration in the rooting medium. Inhibitions in growth by Cd were reduced by addition of organic matter; the amount of alleviation was dependent on both the level of organic matter and the cadmium treatment. In the 0, 0.5 and 1% OM-S mixtures, Cd content in the various tissues was correlated with metal treatment. Tissue levels were markedly reduced for Cd treatments in the 2, 4 and 8% OM-S mixtures, although there was a positive correlation between tissue Cd and the 1.25 and 2.5 Cd treatments. The order of Cd accumulation in the tissues was roots ≫ stems>leaves.

Phytotoxicity of cadmium inhibited by lime

SummaryHeight growth and dry weight accumulation of six-week-old soybeans (Glycine max var. Williams) were severely reduced by 4 ppm CdCl2 in quartz sand culture. This reduction in growth was eliminated by application of 40 ppm Ca(OH)2 (90 kg/hectare plow depth equivalent). CaCO3 at 500 ppm was not effective in preventing cadmium phytotoxicity. re]19760525

Photosynthesis and transpiration of excised silver maple leaves exposed to cadmium and sulphur dioxide.

Abstract Excised leaves of silver maple (Acer saccharinum L.) were exposed to 0, 5, 10 or 20 ppm Cd2+ for 45 h followed by fumigation with 0, 1 or 2 ppm SO2 for 30 min. Net photosynthesis and transpiration were significantly reduced by Cd2+ or SO2 alone. The reduction in net photosynthesis and transpiration of Cd2+ treated leaves was greater in the presence of SO2. Diffusion resistances of leaves to carbon dioxide and water vapour transfer generally increased with both increasing Cd2+ and SO2 concentration. Leaves treated with 5 ppm Cd2+ exhibited increased net photosynthesis and transpiration and decreased resistance to carbon dioxide and water vapour flux. Significant Cd2+/SO2 interactions were found.

Condensed tannins in Leucaena and their relation to psyllid resistance

Leucaena species and hybrids were examined to determine the relative content of condensed tannins and its relationship to susceptibility to defoliation by the Leucaena psyllid (Heteropsylla cubana). The interspecific Leucaena hybrid KX2 (L. leucocephala × L. pallida) was examined for variability of condensed tannin levels. A broad range of condensed tannin values were found which indicate potential for improved forage value through selection for KX2 trees with lower condensed tannin while maintaining psyllid resistance. A significant correlation was not found linking condensed tannins and psyllid resistance.

Leucaena forage analysis using near infrared reflectance spectroscopy

Abstract Leucaena is a fast growing, multipurpose tree planted in tropical regions for many uses including forage. Leaf and leaf + stem material were collected from Leucaena species, varieties, and hybrids grown at two sites in Hawaii and in Australia. Neutral detergent fiber, acid detergent fiber, crude protein, in-vitro dry matter digestibility, and relative condensed tannin were determined by both laboratory and near infrared reflectance spectroscopy (NIRS) procedures. The objective was to evaluate the forage quality of the Leucaena material and to determine the feasibility of using NIRS as a reliable means to determine forage values. Considerable variation within forage quality attributes was found among the species, varieties, and hybrids evaluated, indicating the need for careful selection of Leucaena for forage production systems. Laboratory analyses and NIRS estimations of forage quality attributes were highly correlated, suggesting that NIRS analysis should be considered as an efficient tool for Leucaena forage development programs.

Gibberellin synthesis inhibitors affect electron transport in plant mitochondria

NADH oxidation and cytochrome c reduction rates in the electrontransport chain were determined for mitochondria isolated from leaves of matureEuropean black alder (Alnus glutinosa L.) and exposed to arange of concentrations of the growth retardants flurprimidol andpaclobutrazol.NADH oxidation and cytochrome c reduction were enhanced by low concentrationsofboth compounds whereas higher concentrations reduced electron transport. Thisisthe first report of gibberellin synthesis inhibitors affecting electrontransport in plant mitochondria and provides evidence for another potentialmodeof action of this type of growth retardant.

THE RESPONSE OF ACACIA SCLEROXYLA TUSS. TO MYCORRHIZAL INOCULATION

SUMMARY Seeds of Acacia scleroxyla Tuss., collected from trees in the Subtropical Dry Forest near Mao, Dominican Republic, were germinated and seedlings inoculated with six species of mycorrhizal fungi (Glomus macrocarpum Tul. and Tul., Glomus fasciculatum (Thaxt.) Gerd, and Trappe, Glomus mosseae Nicol, and Gerd., Glomus etunicatum Becker and Gerd., Glomus epigaeum Daniels and Trappe, or Gigaspora margarita Becker and Hall). Seedlings were grown in a greenhouse for 32 weeks and various growth parameters and percent infection of the roots measured. Mycorrhizal infection significantly improved the growth of Acacia scleroxyla seedlings compared to that of nonmycorrhizal seedlings. Growth varied in response to the different fungal species and could have been due to differences in efficacy of the fungal species, differences in percent infection of the root, or a combination of these factors.

GERMINATION OF SEEDS OF AZADIRACHTA INDICA ENHANCED BY ENDOCARP REMOVAL

SUMMARY Seeds of Azadirachta indica A. Juss. were collected from trees in Haiti and the effect of pre-germination treatments were investigated in the laboratory at the Instituto Superior de Agricultura, Santiago, Dominican Republic. Soaking seeds in water for up to 3 days had no effect on germination. Removal of the endocarp improved germination significantly even when seeds were air-dried. Possible physiological mechanisms for the loss of seed viability and the role of the endocarp are discussed including the development of a physical barrier to water and/or gas exchange, inhibitors, and metabolism of fatty acids in the seed.