Respiration leaves

The leaf structure has several important functions, three of which are photosynthesis, transpiration, and respiration (2). Photosynthesis is accomplished by chloroplasts in the leaf, which combine water and COj in the presence of sunlight to form sugars and release O2. This process is shown in Eq. (8-1). 

The effects that changes in vegetation have on soil carbon pools and nutrient availability are also difficult to evaluate. However, several models have been successful in predicting vegetation-soil nutrient relationships because they assume that such changes occur as a result of different rates of decomposition and nutrient release from leaf litter of different taxa 50, 60), Such predictions could be tested and the models refined or parameterized for new taxa by measuring soil nutrient availability and respiration in stands of different species on the same soil type. For example, fifty years ago the U.S. Civilian Conservation Corps (CCC) established such stands as species trial plots measurements in some indicate large differences in soil nutrient availability (48), Further measurements in these stands would now occur at the same time-scale at which we expect the feedback between species replacement and soil processes to occur. 

Fresh leaf is brought to the factory with a few hours of harvesting. Careful handling prevents bruising and allows for the dissipation of heat generated by continuing respiration. It is then subjected to a withering step to reduce leaf moisture from 75-80% to 55-65%. Withered leaf is flaccid and can be worked further without excessive fracture. 

Cutting grass, or more precisely separating leaf tips from lower parts of the grass plant, is not immediately lethal, and even chopping up these tips kills only a small percentage of the cells. The leaves continue to respire they oxidize stored carbohydrates and other foods into carbon dioxide and water, or into intermediate compounds. 

Iron toxicity is a syndrome of disorders associated with large concentrations of Fe + in the soil solution. It is only found in flooded soils. A wide range of concentrations produce the symptoms, from 1000 to only 10mgL in soils with poor nutrient status—especially of P or K—or with respiration inhibitors such as H2S. There are large differences in tolerance between rice varieties. The effects include internal damage of tissues due to excessive uptake of Fe + impaired nutrient uptake, especially of P, K, Ca and Mg and increased diseases associated with imbalanced nutrition, such as brown leaf spot (caused by Helminthospo-rium oryzae), sheath blight (caused by Rhizoctonia solani) and blast (caused by Pyricularia oryzae). 

Physiologic Effects The physiologic effects of ozone depend on its entry into the internal leaf spaces through the stomata. If the plant is resistant to ozone even when stomata remain open, mechanisms of resistance other than stomatal closure must be operative. The physiologic effects measureable with the intact tissue include effects on respiration and photosynthesis. 

Todd reported that the respiration of pinto bean leaves was stimulated by exposure to ozone (at 4 ppm for 40 min). The first measurements were 4 h after the ozone exposure. The respiration rate later declined to the control value. In all cases, increased respiration correlated well with visible injury. MacdowalP confirmed these results, but made an additional observation during the first hour after ozone exposure (at 0.7 ppm for 1 h), and before visible symptoms appeared, respiration was inhibited. The increase in respiration took place only later, when visible symptoms appeared. Dugger and Palmer" reported an increase in respiration in lemon leaf tissue after 5 days of exposure to ozone at 0.15-0.25 ppm for 8 h/day. They reported no morphologic changes at that time. Anderson and Taylor S found that ozone induced carbon dioxide evolution in tobacco callus tissue. The threshold for evolution was about 0.1 ppm for 2 h in the sensitive Bel W,. The ozone concentration required for maximal carbon dioxide evolution was about twice as much in the more resistant cultivar. Formation of roots decreased sensitivity. 

The toxic effects of ozone in plant systems have been studied for some time, yet the actual mechanisms of injury are not fully understood. In addition to visible necrosis which appears largely on upper leaf surfaces, many other physiological and biochemical effects have been recorded ( ). One of the first easily measurable effects is a stimulation of respiration. Frequently, however, respiration may not increase without concomitant visible injury. Furthermore, photosynthesis in green leaves as measured by CO2 assimilation, may decrease. It is well known that ozone exposure is accompanied by a dramatic increase in free pool amino acids ( ). Ordin and his co-workers ( ) have clearly shown the effect of ozone on cell wall biosynthesis. In addition, ozone is known to oxidize certain lipid components of the cell ( ), to affect ribosomal RNA (16) and to alter the fine structure of chloroplasts (7 ). 

Adenosine triphosphate is utilized in portions of the cell other than the mitochondria and chloroplasts therefore, the utilization as well as the production of ATP is of importance to total adenylate status. As a result, it became important to consider total ATP content of plants. When detached pinto bean leaves were exposed to 1,0 yl/1 ozone for 30 min total ATP content of the leaf decreased (12), Since ozone altered leaf ATP content it could also alter the leaf s adenylate status we wished to determine if a correlation existed between alteration in adenylates and the change previously reported in photosynthesis and respiration. Since ATP is readily broken down by adenosine triphosphatases, a reliable method of extraction and quantitative method of ATP analysis was designed for the study (8),... 

S. Brown, Biochem. Educ. 26, 164-167 (1998). Photosynthesis and respiration in leaf slices. 

Effects Arecoline is a central nervous system stimulant. It increases respiration and decreases the work load of the heart. Betel leaf has mild stimulating properties. 

Plants and their individual parts display distinct patterns in their respiratory rate during development. One of the earliest studies on respiratory patterns was conducted on sunflower plants and component parts during an entire growing season (Kidd et al., 1921). In Jerusalem artichokes, total carbon respired from the leaves was calculated from the respiratory rate of different aged leaves x their weight (Hogetsu et al., 1960). The vertical distribution of leaf size (g dwt) and respiratory losses... 

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