Showing papers on "Plant physiology published in 1970"

The effect of nutrient deficiencies on phosynthesis and respiration in spinach

Abstract: Spinach plants were grown in nutrient-culture solutions containing reduced levels of all the macro- and micro-nutrient elements except cobalt and chlorine. The rates of photosynthesis (carbon dioxide fixation in the light expressed on a per unit chlorophyll or per unit fresh-weight basis) and respiration (carbon dioxide evolution in the dark expressed on a per unit nitrogen or per unit fresh-weight basis) for whole plants were measured using infra-red gas analysis techniques. Measurements were made when the plants displayed clear symptoms of deficiency relative to control plants. All nutrient deficiencies except iron and molybdenum depressed photosynthesis when chlorophyll was the basis of calculation; manganese-, copper-, phosphorus- and potassium-deficient plants showed the greatest depression. Alternatively when photosynthesis was calculated on a fresh weight basis calcium was the only deficiency which had no affect. Similarly when respiration was calculated on a nitrogen basis all deficiencies except iron, molybdenum and nitrogen result in depressed rates but when respiration was expressed on a fresh-weight basis potassium deficiency resulted in enhanced respiration rates and nitrogen, phosphorus, sulphur, manganese, zinc and molybdenum deficiencies resulted in reduced respiration rates.

Effect of drought upon rates of photosynthesis, respiration, and transpiration of seedlings of two ecotypes of Douglas Fir. II. Two-year-old seedlings.

Abstract: Rates of photosynthesis, respiration, and transpiration in Douglas-fir seedlings that grew from seed collected in a wet and a dry site were determined under conditions of variable soil-moisture stress. Photosynthetic rates declined sharply after soil-moisture stress of 1 atm was reached, with no major differences between seedlings from the two sources. At both high and low tensions of soil moisture, respiration and transpiration rates were higher for seedlings from the wet site than for those from the dry site. Seedlings from the xeric environment had higher photosynthetic rates at high relative turgidities and lower at low relative turgidities than seedlings from the mesic sites. Over a wide range of soil-moisture tensions, relative turgidity of seedlings from the xerophytic source varied less than that of seedlings from the mesophytic source.

Growth potential of Douglas Fir seedlings during dormancy.

Abstract: Summary The three experiments indicated that individual buds were the receptors for the growth stimulus produced by extended photoperiods during the autumn and winter. No evidence of transport of growth stimulatory materials from active to dormant bud was noted. Buds whose chilling requirements were fully satisfied initiated growth in response to favourable temperatures rather than to long photoperiods. Initiation of activity by lateral cambia required material exported from both expanding buds and mature foliage. No significant correlation between shoot and root growth was found. Although neither active buds nor applications of exogenous IAA or GA stimulated roots growth, both root elongation and initiation were found to be dependent upon some substance or substances, presumably hormones or carbohydrates, exported from mature foliage. Findings indicated that seedling physiology during the dormant period may be controlled by a changing balance in growth inhibitors and promoters.

Stimulation of spore germination of wood-decomposing hymenomycetes by carbon dioxide.

Abstract: The effect of carbon dioxide on the spore germination of 23 wooddecomposing Hymenomycetes was investigated by introducing 1 %, 5 %, and 20 % carbon dioxide air mixtures into desiccators, in which spores were germinated on Hagem agar. Compared to ordinary air, low concentrations ( 1 % and 5 % ) markedly stimulated the germination rate of several species . Species growing in living tree stems were stimulated most effectively (Spon,gipellis borealis, Polyporus squamosus, Pholiota aurivella and Fomitopsis annosa) . Stimulation took place at different pH values and seems to be independent of the acidifying action of carbon dioxide. Ecological aspects of the stimulation are discussed.

Some properties of O-methyltransferase from Bamboo shoot.

Abstract: -The incubation of CA, 5-HFA and TCA with sliced bamboo shoot in the presence of methionineCHa gave radioactive FA and SA. On the other hand, the incubation of those compounds with sliced gingko shoot yielded only FA from CA and did not SA from 5-HFA and TCA. The enzyme preparation obtained from bamboo shoot was fractionated by (NH4)2S04and iso-electric point precipitations and column chromatographies on DEAE-cellulose. Variation of the ratios (SA/FA) which were obtained by assay of 0methyltransferase are indicative of possible presence of two enzymes in the bamboo enzyme preparation. The results are discussed in relation to the biochemical differences of the methoxyl patterns in lignins between angiosperms and gymnosperms.

The Physiology of Germination

Abstract: From the standpoint of survival and subsequent growth of a plant, sprouting, or germination, of a seed is of the highest importance. Since germination is under the control of environment to a greater or lesser degree, plant distribution is strongly influenced by this process. Ecology studies the interactions of organisms with their environment and is thus concerned with plant distribution. Since study of the control mechanisms of germination provides a number of interesting possibilities for research in plant physiology, this is an excellent example of an area where ecology and physiology overlap in an interesting way.