Showing papers on "Plant morphology published in 1985"

Plant Morphological and Biochemical Responses to Field Water Deficits I. Responses of Glutathione Reductase Activity and Paraquat Sensitivity

Abstract: The effects of water deficits on plant morphology and biochemistry were analyzed in two photoperiodic strains of field-grown cotton (Gossypium hirsutum L.). Plants grown under dryland conditions exhibited a 40 to 85% decrease in leaf number, leaf area index, leaf size, plant height, and total weight per plant. Gross photosynthesis decreased from 0.81 to 0.47 milligram CO(2) fixed per meter per second and the average midday water, osmotic, and turgor potentials decreased to -2.1, -2.4, and 0.3 megapascals, respectively.There was a progressive increase in glutathione reductase activity and in the cellular antioxidant system in the leaves of stressed plants compared to the irrigated controls. The stress-induced increases in enzyme activity occurred at all canopy positions analyzed.Irrigation of the dryland plots following severe water stress resulted in a 50% increase in leaf area per gram fresh weight in newly expanded leaves of both strains over the leaves which had expanded under the dryland conditions. Paraquat resistance (a relative measure of the cellular antioxidant system) decreased in the strain T25 following irrigation. Glutathione reductase activities remained elevated in the T25 and T185 leaves which were expanded fully prior to irrigation and in the leaves which expanded following the irrigation treatment.

Morphology and growth in seedlings of several C4, perennial grasses.

Abstract: Establishment of forage grasses depends upon their ability to compete for resources in the critical seedling establishment phase. Desirable native grass species are generally considered to be more difficult to establish from seed than the introduced Old World bluestems (Bot~ocUut spp.), although comparative data are generally lacking. This study compared the responses of morphological attributes commonly associated with seedling vigor and some growth parameters in 17 perennial, C4 grasses including 5 native and 12 Old World bluestems. Plants were grown in a greenhouse under well-watered and limited watering regimes. The objective was to document differences in morphology and growth among these grasses from emergence through 7 weeks post emergence. The Bothriochloa species generally rated higher than the native species in morphological characters commonly associated with seedling vigor. The exotics produced as much or more biomass and had more leaf area per plant, more tillers, and leaves per tiller than the natives. Although the native grasses produced less leaf area, the cost of these leaves in terms of biomass per unit area was higher than in the introduced grasses. The natives tended to partition relatively more biomass aboveground and more of this to leaves, rather than sheaths plus stems, than the Old World bluestems. However, partitioning of total plant biomass among roots, sheaths plus stems, and leaf blades was remarkably insensitive to water stress in all entries. Approximately one-third of total biomass was partitioned among kaf blades, sheaths plus stems, and roots, respectively, with sheaths+stems tending to be a slightly smaller fraction than the other 2 components. Recurring water stress cycles reduced most parameters significantly and generally accentuated the normal ontogenetic decline in relative growth and unit rates. Across all entries, total plant biomass and leaf blade area were reduced over 4m by a limited watering regime. Although water stress reduced the size of the assimihttory surface, the remaining leaves were more effkient in the production of new biomass. This response correlated with an increase in specific leaf weight under water stress. Successful establishment of forage grasses from seed depends on numerous environmental factors (see Vallentine 1980) which interact with the plant’s genetic component during germination, emergence, and post-emergence growth. Plant vulnerability to environmental stresses is particularly high during seedling establishment because of limited food reserves (Johnson 1984) resulting from small seed size and limited photosynthetic capacity. The amount of food reserves stored in the endosperm is an important factor related to establishment potential (Davies 1967). Also contributing to this vulnerability is the lack of a well-developed root system. Frequently, competitive advantages gained during the seedling stage are maintained in the mature plant stage (Johnson 1984). Variability in establishment success among species and genotypes within species is common knowledge, and high success is often associated with rapid germination, rapid root and top growth, a robust growth habit, and resistance to stress (McKell 1972). These traits are collectively referred to as seedling vigor. Numerous techniques for assessing seedling vigor have been developed (reviewed by Whalley and McKelll973) and much effort has been expended to enhance vigor in forage plant germplasm (Kneebone 1972). Thirty years of research have shown that selections from the Authors are plant physiologists, USDA-AR& Southern Plains Range Research Station, 2000-18th Street, Woodward, Okla. 73801. C.L. Dewald provided the plant materials used in this study. Tom Popham and George Hilton are acknowledged for their assistance with the statistical analyses. Manuscript accepted March 13, 1985. genus Bothriochloa (Asiatic or Old World bluestems) can contribute significantly to beef production and soil conservation in the Southern Great Plains (Sims and Dewald 1982). The Old World bluestems have been found to exhibit relatively high seedling vigor at Woodward, Okla. in comparison with native species (C.L. Dewald, pers. comm.). Harlan et al. (1958) noted that ecologically, the Old World bluestems are best fitted to some stage of secondary succession and that they tend to increase under grazing pressure. They also noted that these grasses reproduce freely by seed, tend to be somewhat weedy, and are generally easily established in plantings. Experience has shown that establishment of stands of climax, decreaser species in the Southern Plains usually requires 2 growing seasons while only 1 is required to establish the Old World bluestems. Of the 3 phases of seedling establishment (germination, emergence, postemergence growth), it was felt that a manager would have least control over the last phase since high quality seed, proper seedbed preparation, and timing of planting with periods of soil moisture sufficient to ensure germination would reduce the risk associated with phases I and 2. Therefore, phase 3 was isolated for study. The objective of the study was to determine differences in morphology and growth behavior among 5 native and 12 Old World bluestem perennial forage grasses from emergence through I2 weeks post emergence under near optimum conditions which could be used as indices of comparative performance potential. Because post-emergence failure is frequently associated with drought stress (Vallentine 1980, Whalley and McKell 1973) and because drought conditions can be prevalent during the normal period for establishing warm-season grasses, a suboptimal soil water treatment was included to assess relative departure of the measured parameters from potential. Materials and Methods Plant Materials and Culture Seventeen perennial, warm-season grasses, including 5 native and 12 exotic Old World bluestems, were included in this study (Table 1). Woodward sand bluestem is a leafy grass of medium height with good seed production characteristics. Hachita blue grama is a relatively tall and productive selection compared to blue grama selections in general. Two switchgrass varieties were included: one is a robust upland type (Caddo), and the other (Kanlow) is adapted to lowland sites. Western indiangrass is an experimental strain selected for ease of establishment and it has low dormancy and rapid emergence compared to other indiangrass cultivars such as Cheyenne and Osage. The Old World bluestems included 3 species. B. cuucusicu and B. intermediu have secondarily branched inflorescences, B. ischuemum does not. B. cuucusicu has a relatively small crown diameter (basal spread) compared to the other.2 species.‘B. cuucusicu, B. intermediu var. indicu and B. ischuemum var. ischuemum exhibit early seed maturity compared to B. intermediu var. montunu. A gradation of leaf widths is present in these grasses. Wide-leaf types include B. intermediu var. montunu. medium-leaf types include B. cuucusicu and 8. ischuemum var. ischuemum. while B. intermediu var. indicu is composed of narrow-leaf types. WW-477 is an introgression between the B. intermediu and B. ischuemum and has many characteristics in common with King Ranch bluestem (B. ischuemum). WW-Spar bluestem, WW-535, and WW-604 are 3 of 30 yellow bluestem strains blended together to make ‘Plains’bluestern (Taliaferro et al. 1972). Potential variability in post-emergence seedling growth resultJOURNAL OF RANGE MANAGEMENT 38(e), November 1985 Table 1. Idenilfication of piant materials and seed weigbht. Entry Scientific name Cultivar/ Accession Country of Origin Air-valve setting&i> -Seed SizeMean U> SD Native Species: 1 Andropogon ha/Iii 2 Ponicum virgatum 3 ,t 4 Sorghasrrum nutans 5 Bouteloua gracilis Old World Bluestems (Bothriochloa spp.): 6 B. caucosica 7 ,, 8 B. intermedia var. indica 9 9, 10 ,, II ,, var. montana 12 n 13 B. ischaemum var. ischaemum 14 . . 15 9. 16 9. 17 1, var. songorica Woodward sand bluestem Caddo switchgrass Kanlow switchgrass WW-Western indiangrass (Woodward experimental) Hachita blue grama Caucasian bluestem, WW4%2 Caucasian bluestem, WW-765 ww-517 ww-811 ww-822 ww-857 WW-886 Ganada bluestem WW-Spar bluestem ww-535 ww-604 ww477 U.S.A. ,. 9, 9.