Involvement Of K+ In Leaf Movements During Suntracking :: essays research papers

Involvement of K+ in Leaf Movements During SuntrackingIntroductionMany plants tailor their leaves in response to directional watery places.Heliotropic movements, or movements that are affected by the sun, are commonamong plants be to the families Malvaceae, Fabaceae, Nyctaginaceae, andOxalidaceae. The leaves of many plants, including Crotalaria pallida, exhibitdiaheliotropic movement. C. pallida is a woody shrub native to South Africa.Its trifoliate leaves are connected to the petiole by 3-4 mm broad pulvinules(Schmalstig). In diaheliotropic movement, the plants leaves are oriented perpendicular to the suns rays, thereby maximizing the interception ofphotosynthetically active radiation (PAR). In some plants, however not all, hisresponse occurs particularly during the first light and late afternoon, when thelight is coming at more of an angle and the water stress is not as consummate(a)(Donahue and Vogelmann). Under these conditions the lamina of the leaf iswithin little th an 15 from the normal to the sun. Many plants that exhibitdiaheliotropic movements also show paraheliotropic response as well.Paraheliotropism minimizes water loss by reducing the amount of light inattentiveby the leaves the leaves orient themselves parallel to the suns rays. Plantsthat exhibit paraheliotropic behavior usually do so at midday, when the sunsrays are perpendicular to the ground. This reorientation takes place only inleaves of plants that are capable of nastic light-driven movements, such as thetrifoliate leaf of coral tree spp. (Herbert 1984). However, this phenomenon hasbeen observed in other legume species that exhibit diaheliotropic leaf movementas well. Their movement is temporarily transformed from diaheliotropic toparaheliotropic. In doing so, the interception of solar radiation is maximizedduring the dawning and late afternoon, and minimized during midday. The leavesof Crotalaria pallida also exhibit nyctinastic, or sleep, movements, in whichthe leaves fold down at night. The solar tracking may also come through acompetitive advantage during primeval growth, since there is little shading, andalso by intercepting more radiant heat in the early morning, thus height leaftemperature nearer the optimum for photosynthesis.intact to understanding the heliotropic movements of a plant isdetermining how the leaf detects the angle at which the light is incident uponit, how this perception is transduced to the pulvinus, and finally, how thissignal can effect a physiological response (Donahue and Vogelmann).In the species Crotalaria pallida, blue light seems to be the wavelengththat stimulates these leaf movements (Scmalstig). It has been implicated in thephotonastic unfolding of leaves and in the diaheliotropic response inMactroptilium atropurpureum and Lupinus succulentus (Schwartz, Gilboa, andKoller 1987). However, the light receptor involved can not be determined fromInvolvement Of K+ In Leaf Movements During Suntracking essays research papers Involvement of K+ in Leaf Movements During SuntrackingIntroductionMany plants orient their leaves in response to directional light signals.Heliotropic movements, or movements that are affected by the sun, are commonamong plants belonging to the families Malvaceae, Fabaceae, Nyctaginaceae, andOxalidaceae. The leaves of many plants, including Crotalaria pallida, exhibitdiaheliotropic movement. C. pallida is a woody shrub native to South Africa.Its trifoliate leaves are connected to the petiole by 3-4 mm long pulvinules(Schmalstig). In diaheliotropic movement, the plants leaves are orientedperpendicular to the suns rays, thereby maximizing the interception ofphotosynthetically active radiation (PAR). In some plants, but not all, hisresponse occurs particularly during the morning and late afternoon, when thelight is coming at more of an angle and the water stress is not as severe(Donahue and Vogelmann). Under these conditions the lamina of the leaf iswithin less than 15 from the normal to the sun. Many plants that exhibitdiaheliotropic movements also show paraheliotropic response as well.Paraheliotropism minimizes water loss by reducing the amount of light absorbedby the leaves the leaves orient themselves parallel to the suns rays. Plantsthat exhibit paraheliotropic behavior usually do so at midday, when the sunsrays are perpendicular to the ground. This reorientation takes place only inleaves of plants that are capable of nastic light-driven movements, such as thetrifoliate leaf of Erythrina spp. (Herbert 1984). However, this phenomenon hasbeen observed in other legume species that exhibit diaheliotropic leaf movementas well. Their movement is temporarily transformed from diaheliotropic toparaheliotropic. In doing so, the interception of solar radiation is maximizedduring the morning and late afternoon, and minimized during midday. The leavesof Crotalaria pallida also exhibit nyctinastic, or sleep, movements, in whichthe leaves fold down at night. The sol ar tracking may also provide acompetitive advantage during early growth, since there is little shading, andalso by intercepting more radiant heat in the early morning, thus raising leaftemperature nearer the optimum for photosynthesis.Integral to understanding the heliotropic movements of a plant isdetermining how the leaf detects the angle at which the light is incident uponit, how this perception is transduced to the pulvinus, and finally, how thissignal can effect a physiological response (Donahue and Vogelmann).In the species Crotalaria pallida, blue light seems to be the wavelengththat stimulates these leaf movements (Scmalstig). It has been implicated in thephotonastic unfolding of leaves and in the diaheliotropic response inMactroptilium atropurpureum and Lupinus succulentus (Schwartz, Gilboa, andKoller 1987). However, the light receptor involved can not be determined from