Browsing by Subject "Plants -- Drought tolerance"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Genetic control of development traits related to productivity of grain sorghum under various soil water supplies(Texas Tech University, 1987-08) Phipps, Michael RSix inbred lines of grain sorghum (Sorghum bicolor L. Moench) were chosen on the basis of their diversity for several developmental and productivity traits. These parents (3 R-lines and 3 B-lines) were crossed in a complete diallel design (fixed model, without parents) in order to study the inheritance of the developmental and productivity traits. In addition, the 3 R-lines were crossed with 3 A-line counterparts to the B-lines for study of male sterile cytoplasm effects upon these traits. The crosses were performed in a greenhouse by the hand-emasculation method. The 39 F, progenies were grown in the field at Brownfield, Texas in a loamy-sand soil under 100% ETa and 50% Eta irrigation levels in 1985 and 1986. Measurements were conducted for developmental traits and productivity traits. From these measurements, several whole plant water use efficiency traits involving productivity per unit leaf area were calculated. Considerable genetic variation was found for most developmental and productivity traits studied. For some traits, this genetic variation was consistent over irrigation regimes and years. However, for several traits this genetic variation differed among irrigation regimes and years. Most of the genetic variation was accounted for by additive genetic effects for most traits while some traits were also controlled by non-additive genetic effects and a few traits exhibited significant reciprocal and maternal effects. Thus most traits studied can be genetically improved in these lines through breeding although some will require careful choice of both parents in hybrid combinations and many may require selection to be conducted over several environments. Seed number was found to be the predominant grain yield component. Grain yield was closely associated with total above-ground biomass suggesting genetic improvement of harvest index would be difficult. Leaf area was associated with grain yield suggesting that leaf area, rather than number of leaves, has the greater effect upon grain yield.Item Osmotic adjustment: a drought tolerance mechanism in sorghum(Texas Tech University, 1988-08) Girma, Fekade SelassieLack of an adequate water supply is the primary limitation to plant productivity world-wide. Grain sorghum (Sorghum bicolor L. Moench) production occurs predominantly in semiarid regions of the world where random drought is common. A number of drought resistance mechanisms are known to exist among plant species which allow adaptation to water deficits. Osmotic adjustment, the lowering of osmotic potential (øn) by net solute accumulation, is a drought resistance mechanism that is proposed to allow tolerance of tissue dessication by maintaining turgor and those developmental and physiological processes dependent upon turgor (cell expansion, stomatal opening, chloroplast activity, etc.). Despite considerable evidence for the lowering of øn due to water stress, limited information is available on the mechanisms involved and the association between osmotic adjustment and plant performance in response to water deficits. A field experiment was conducted to determine the mechanisms involved in øn changes and the association between osmotic adjustment and physiological parameters in grain sorghum. Degrees of plant water stress were induced by varying the soil water supply through differential irrigation. Leaf water potential (øw ), øn, stomatal conductance, and photosynthesis were measured diurnally on selected days prior to flowering and during grain filling stage. Partitioning of the total diurnal change in øn indicated that dehydration and net solute accumulation were the major mechanisms for diurnal change in øn. Osmotic adjustment maintained turgor pressure over a wide range of øw. Despite the maintenance of turgor pressure by osmotic adjustment, stomatal conductance and photosynthesis declined as øw decreased. Results from this study indicate that osmotic adjustment does not maintain stomatal conductance and photosynthesis in grain sorghum.Item Osmotic adjustment: a drought tolerance mechanism in sorghum(Texas Tech University, 1988-05) Girma, Fekade SelassieLack of an adequate water supply is the primary limitation to plant productivity world-wide. Grain sorghum (Sorghum bicolor L. Moench) production occurs predominantly in semiarid regions of the world where random drought is common. A number of drought resistance mechanisms are known to exist among plant species which allow adaptation to water deficits. Osmotic adjustment, the lov/ering of osmotic potential (ψn) by net solute accumulation, is a drought resistance mechanism that is proposed to allow tolerance of tissue dessication by maintaining turgor and those developmental and physiological processes dependent upon turgor (cell expansion, stomatal opening, chloroplast activity, etc.). Despite considerable evidence for the lowering of ψn due to water stress, limited in£ormation is available on the mechanisms involved and the association between osmotic adjustment and plant performance in response to water deficits. A field experiment was conducted to determine the mechanisms involved in ψn changes and the association between osmotic adjustment and physiological parameters in grain sorghum. Degrees of plant water stress were induced by varying the soil water supply through differential irrigation. Leaf water potential (ψw), ψn, stomatal conductance, and photosynthesis were measured diurnally on selected days prior to flowering and during grain filling stage. Partitioning of the total diurnal change in ψn indicated that dehydration and net solute accumulation were the major mechanisms for diurnal change in ψn. Osmotic adjustment maintained turgor pressure over a wide range of ψw Despite the maintenance of turgor pressure by osmotic adjustment, stomatal conductance and photosynthesis declined as ψw decreased. Results from this study indicate that osmotic adjustment does not maintain stomatal conductance and photosynthesis in grain sorghum.