Showing papers on "Plant morphology published in 2004"

Drought-induced Leaf Senescence and Horticultural Performance of Transgenic PSAG12-IPT Petunias

Abstract: Cytokinins have been shown to delay the onset of leaf senescence. The focus of this project was to produce transgenic petunia (Petunia ×hybrida) plants that over-produced endogenous cytokinins in a senescence specifi c manner. This was achieved by transforming plants with the IPT (isopentenyl transferase) gene driven by the senescence-associated transcriptional promoter, PSAG12. Two independent transgenic events produced T1 and T2 generation seedling lines that demonstrated the desired nonsenescent phenotype in progeny trials. These lines were used to evaluate the horticultural performance of PSAG12-IPT petunia plants in terms of delayed senescence, rooting of vegetative cuttings, lateral branch growth, fl ower number, fl oral timing, and fruit set. Although both lines displayed a delayed senescence phenotype the two PSAG12-IPT transgenic lines differed from each other in regard to other horticultural traits. In addition to delayed leaf senescence, line I-1-7 also demonstrated a decrease in adventitious rooting and an increased number of branches during plant production. Line I-3-18 also demonstrated a delayed leaf senescence phenotype; however, plants of this line were not greatly altered in any other horticultural performance traits in comparison to wild-type 'V26ʼ. IPT transcript was detected in young fully expanded leaves of both lines, although mRNA levels were higher in I-1-7 plants. A greater than 50-fold increase in IPT transcript abundance was detected in leaves of transgenic plants following drought stress. These results demonstrate that it is possible to use PSAG12-IPT to produce transgenic plants with delayed leaf senescence but differences in plant morphology between transgenic lines exist, which may alter horticultural performance characteristics. Senescence is the fi nal developmental process in the lifecycle of a leaf. It is a process through which the nutrients contained within the macromolecules (e.g., chlorophyll, proteins, nucleic acids) of leaf cells are metabolized to basic components and trans- ported to the growing shoot and reproductive organs of the plant. This strategy imparts a survival advantage for plants that grow under adverse conditions where nutrients are limiting (Nooden, 1988). Natural leaf senescence in many plants is characterized by yellowing or chlorosis of the lower leaves as nutrients and other components of the cells are degraded (esp. chlorophyll). In horticultural terms, chlorosis can decrease the aesthetic appear- ance and thereby decrease the salability of that plant. With so much at risk, it is no wonder that growers and researchers alike have tried to understand the components of leaf senescence in order to prevent it. One way to prevent leaf senescence is through the manipulation of cytokinins. Cytokinins are an important class of plant hormones that infl uence numerous aspects of plant growth and development. They have been shown to delay and, in some cases, reverse the leaf senescence process (Gan and Amasino, 1996). There is an inverse correlation between the concentration of cytokinins in leaves and the magnitude of leaf senescence. This can be dramati- cally seen as the formation of green islands on leaves infected by cytokinin-producing pathogens, such as Helminthosporium teres (Angra and Mandahar, 1991). The use of applied cytokinins to prevent senescence is limited because it is diffi cult to supply them

Construction of a comparative RFLP map of Echinochloa crus-galli toward QTL analysis of flooding tolerance.

Abstract: To analyze quantitative trait loci (QTLs) affecting flooding tolerance and other physiological and morphological traits in Echinochloa crus-galli, a restriction fragment length polymorphism (RFLP) map was constructed using 55 plants of the F2 population (E. crus-galli var. praticola × E. crus-galli var. formosensis). One hundred forty-one loci formed 41 linkage groups. The total map size was 1,468 cM and the average size of linkage groups was 35.8 cM. The average distance between markers was 14.7 cM and the range was 0–37.2 cM. Early comparisons to the genetic maps of other taxa suggest appreciable synteny with buffelgrass (Pennisetum spp.) and sorghum (Sorghum spp.). One hundred ninty-one F2 plants were used to analyze QTLs of flooding tolerance, plant morphology, heading date, number of leaves, and plant height. For flooding tolerance, two QTLs were detected and one was mapped on linkage group 24. Other traits, including plant morphology, heading date, number of leaves, and plant height were highly correlated. Three genomic regions accounted for most of the mapped QTLs, each explaining 2–4 of the significant marker-trait associations. The high observed correlation between the traits appears to result from QTLs with a large contribution to the phenotypic variance at the same or nearby locations.

Maricá - Mimosa bimucronata.

Abstract: Nomes vulgares no Brasil: alagadiço, em Pernambuco; amorosa, na Paraíba; angiquinho, no Paraná; arranha-gato, em Minas Gerais; espinheira; espinheira-de-cerca; espinheira-de-maricá; espinheiro, em Alagoas, em Pernambuco, no Rio Grande do Sul, em Santa Catarina e no Estado de São Paulo; espinheiro-de-cerca; espinheiro-de-maricá, em Santa Catarina; espinho, juqui-de-cerca, maricazeiro, no Estado do Rio de Janeiro; espinho-roxo; espinho-de-maricá, em Pernambuco e no Estado de São Paulo; silva, no Rio Grande do Sul e em Santa Catarina; e unha-de-gato, no Paraná e no Estado do Rio de Janeiro.

Aspectos morfofisiológicos da goiabeira cultivar Paluma - DOI: 10.4025/actasciagron.v26i1.1960

Abstract: In order to characterize morphophysiological aspects of guava tree ‘Paluma’, all the leaves of a quadrant of the canopy were collected from three plants representative of a commercial orchard (spaced: 7x5m). At the end of the harvest period, the number of leaves and the leaf area of the quadrant, the diameter of the canopy and the productivity of the orchard were determined. These data were used to estimate mean leaf area (LA), total plant leaf area (PLA), total number of leaves per plant (NLP), leaf area index (LAI), and plant “productive efficiency” (fruit production per plant/PLA). PLA was 151.2m2, LA 40.9cm 2 , LAI 6.7, productivity 323.7kg per plant, and “productive efficiency” of 0.467 and 3.054m 2 leaf area were necessary to produce 1kg fruit on a fresh and dry base, respectively. We may conclude that the ‘Paluma’ guava tree is a plant with high “productive efficiency” compared with others species