Paul J. Kramer

The Physiological Ecology of Woody Plants

How Woody Plants Grow. Physiological and Environmental Requirements for Tree Growth. Establishment and Growth of Tree Stands.Radiation. Temperature. Soil Properties and Mineral Nutrition. Water Stress. Soil Aeration, Compaction, And Flooding. Air Pollution. Carbon Dioxide. Fire. Wind. Cultural Practices. Each Chapter Includes References. Index.

Carbon Dioxide Concentration, Photosynthesis, and Dry Matter Production

It has been suggested the increase in atmospheric CO/sub 2/ produced by the burning of fossil fuels will be to some extent counteracted by an increase in carbon fixation by photosynthesis. This hypothesis is based on the assumption that the rate of photosynthesis is limited chiefly by CO/sub 2/ concentration. The effects on photosynthesis and dry matter production by increased levels of CO/sub 2/ are examined here. (ACR)

EFFECTS OF ATMOSPHERIC CO2 CONCENTRATION AND WATER STRESS ON WATER RELATIONS OF WHEAT

Water status and growth responses of wheat (Triticum aestivum L. [GWO-1809]) to increased CO2 concentration and water stress were studied in controlled-environment chambers. Plants were grown in 350 μl/ liter or 1,000 μl/liter CO2 at similar temperature, irradiance, and photoperiod conditions. Groups of plants were subjected to water stress by withholding irrigation for one or two cycles of treatment. In most treatments, decreasing leaf water potential was correlated with decreasing osmotic potential. In leaves grown in both low and high CO2 concentrations, the osmotic potentials were lower during the second stress cycle than during the first cycle. The stomata of plants in the low CO2 concentration closed at a higher leaf water potential than those in the high CO2 concentration. Stem and head production was greater in plants grown in high CO2 concentrations than those grown in low CO2, perhaps the result of turgor-pressure maintenance as leaf water potential decreased. In controlled-environment chambers, wheat plants adapted to water stress, apparently because of high CO2 concentration and repeated stress cycles.

Growth, Carbon Dioxide Exchange, Transpiration, and Transpiration Ratio of Pineapple

Measurements of growth, carbon dioxide exchange, transpiration, and transpiration ratio were made for pineapple (Ananas comosus [L.] Merr.) plants. During the experimental period, their growth rate was 0.015-0.018 g increase in dry weight per day per 100 cm2 of average leaf area. Carbon dioxide exchange was recorded for 24 hr. During the first part of the light period, CO2 was given off, but uptake began in mid-afternoon and continued through the dark period. This pattern of uptake is common in plants exhibiting a crassulacean type of acid metabolism. From the same measurements, the calculated theoretical rate of net photosynthesis for pineapple was 0.5-0.7 mg/hr per 100 cm2 of leaf area. Transpiration proceeded at a rate of 0.02-0.05 g/hr per 100 cm2. Both these values are lower than those for several crop plants. The transpiration ratio for pineapple, 50, was determined from values for gain in dry weight and water loss during the experimental period of 80 days. This also is considerably less than the values for other crop plants and for trees. Since its transpiration ratio and rate of water loss are low, pineapple probably can maintain high levels of productivity in regions where water is limited.

The measurement of water deficits in broadleaf plants

SummaryA review of past work and a comparison of the well-known disk technique with Stockers whole leaf method for determining water deficit of some hardwood trees reveals confusion in existing terms and methods. The water relations of leaf disks cut from broadleaf trees cannot be assumed to be the same as whole leaves, since the excised disk usually requires more water per unit weight to saturate. Stockers term wasser defizit (WD) and the whole leaf method, when modified to allow shorter equilibration schedules, remain the best way to express and measure water deficits in forest trees.

Transpiration and the Ascent of Sap

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Relationship between Growth and Nitrogen Accumulation for Vegetative Cotton and Soybean Plants

Experiments were conducted to determine whether the nitrogen absorption function of the roots is directly related to the photosynthate supplying function of the leaves under steady-state conditions during vegetative growth phase of cotton (Gossypium hirsutum L) and soybean (Glycine max [L.] Merrill) plants. A direct relationship between these two functions would imply a balanced interdependence and contradict the views that growth of all plant parts is dependent on carbohydrate supplied by the leaves and that nitrogen uptake is dependent only on existing root and soil characteristics. Plants were grown under both artificial light in CERs and natural light in air-conditioned greenhouses, at three thermoperiods, and with three levels of nutrient supply. The data show that RGRR and RARNP were not significantly different within thermoperiod or nutrient supply and agree with those obtained in a previous experiment with tobacco (Nicotiana tabacum L.) The results suggest that plant growth models should be based on the balanced interdependence of the nitrogen absorption and photosynthate supplying functions

Measurement of plant water status: Historical perspectives and current concerns

SummaryThe slow development of concepts and methods for evaluating plant water status is reviewed. These include visual symptoms such as wilting and leaf rolling, measurement of water content, osmotic potential, and total water potential. The best method depends on the objectives of the user, but none of the methods are very well correlated with the effects of water stress on enzyme-mediated processes. Although some investigators claim that relative water content is better correlated with physiological processes than water potential, the latter has the advantage of providing results in well recognized physical units that apply to both plant and soil water status.

Absorption of water by plants

This review is concerned primarily with the nature and origin of the forces bringing about movement of water from soil or other media surrounding roots into the conducting elements of the xylem, and with those internal and external factors which affect the rate of such movement. Absorption of water is not an independent process, but is closely related to other processes included in the domain of plant water relations. The rate of water intake is markedly affected by the rate of transpiration and by the extent and condition of the root systems. It is also affected by such environmental factors as the available moisture content of the soil, soil temperature, soil aeration, and to a lesser extent by the kind and concentration of ions in the soil. Some phases of the work discussed in this review naturally are incomplete and do not permit formulation of definite conclusions concerning certain aspects of the absorption problem. Where the writer has drawn conclusions or made generalizations they seem to be those most justifiable on the basis of the available evidence. It is realized, however, that as knowledge of these processes increases it may be necessary to modify some of the present conclusions. It is impossible to cite all the literature, but most of the papers cited have bibliographies in which the reader can locate other papers dealing with any particular phase of the field.

Relative growth and nutrient accumulation rates for tobacco

SummaryTobacco plants (Nicotiana tabacum L.) were grown from transplanting until floral expression in the phytotron units of Southeastern Plant Environment Laboratories to evaluate the relationship between relative growth rate (RGR) and relative accumulation rates (RAR) of N, P, K, Ca, and Mg. RAR is calculated to be analogous to RGR. Plants were grown in both controlled-environment rooms with artificial light and air-conditioned greenhouses with natural light at three temperature conditions and three application rates of N-P-K. RGR and RAR were calculated only for the period of grand growth which occurred within the interval from 7 to 32 days after transplanting.In general, neither RGR nor RAR were affected by temperature or nutrient level. However, both temperature and nutrient level affected dry matter accumulation of the plants apparently by an influence on the rapidity with which plants adjusted to their new environment during the initial 7-day interval after transplanting. RAR for P and K were coequal with RGR of the whole plant; thus, the concentrations of P and K within the plant tended to remain constant during growth. RAR for N, Ca, and Mg were less than RGR for the whole plant; thus, internal concentrations of these nutrients declined during growth. RAR of N, Ca, and Mg for the whole plant were equivalent to RGR of the roots. As a rationale for the association of RGR of roots and RAR of N, it is proposed that the soluble carbohydrate pool in the roots concurrently influences both N absorption, as NO3-, and growth of new roots of immature plants.