March 1959, Volume 8 Issue 3

 

          Research Articles
Studies on thc Carbohydrate Metabolism of Bai-lan Melons. I. The Accumulation of Sugars and Ascorbic Acids During Fruit Development and Ripening Periods
Author: Lu Chung-shu, Wang Pong-hsi
Journal of Integrative Plant Biology 1959 8(3)
      
    Determinations on the sugars and ascorbic acid content of Bai-Lan melons were made during fruit development and ripening periods. Changes in the intensities of sucrose synthesis and hydrolysis of fruits and leaves of different ages were also measured by the vacuum infiltration method. Total sugars increased continuously throughout the growing period, but the rate of increment was much accelerated during the ripening period of the fruit. The maximal content of total sugars, which ranged from 6.68% to 8.07% on a basis of fresh weight, was observed at full maturity. The variation of starch content followed a similar course as did the total sugars. During the early stages of fruit development, there was a steady increase in reducing sugars, whereas the amount of sucrose was insignificant. After the first 30 days of fruit development, when the enlargement of fruit size was almost completed, however, a gradual decline in reducing sugars anti a concomitant rapid increase in sucrose were noted. The maximal concentration of sucrose, which constituted more than 70% of the total sugars of mature fruit, was attained at the time of full maturity. Changes in the concentrations of glucose and fructose were similar to that of reducing sugars, but the percentage of glucose was usually higher than that of fructose. It was found that the enzymatic hydrolysis of sucrose was predominated over the synthetic process in young, actively growing fruits. However, the direction of the enzymatic reactions changed in favor of the synthetic process during the ripening period of the fruit. On the other hand, the ratio of synthesis/hydrolysis of sucrose in leaves was changed from a high to a low value during the period of ageing. The significance of these findings in sugar accumulation of fruits and in the interdependence of physiological functions between leaves and fruits is discussed. The concentration of ascorbic acid decreased from the beginning of the fruit growing period, reached a maximum at about 30 days after blossoming, and then increased rapidly until maturity. The importance of the results in determining the proper stage of maturity for picking of Bai-Lan melons is indicated.
Abstract (Browse 2045)  |  Full Text PDF       
A Study on the Physiology of After-ripening of Wheat Grains
Author: T. F. Chao, F. T. Wang, S. Wang and T. P. Tsai
Journal of Integrative Plant Biology 1959 8(3)
      
    Studies had been carried out on the after-ripening of wheat grains during 1957 and 1958. The results obtained are summarized as follows: 1. During the period of after-ripening (1每2 month), determinations on the rate of respiration were made at intervals of one week, it indicated that the differences are not significant. The grains at different state of after-ripening (germination ranging from 2% to 99%) had similar oxygen consumption. The breakage of seed coat makes the gas exchange easily, which results to the end of after-ripening, as general beleived, seems questionable. 2. Take-off the pericarp only or together with the seed coat resulted an increase in percentage of germination for dormant grains, but the effect of this treatment was much significant as the grogress of after-ripening close to the end. It indicated that some biochemical changes should occurred during after-ripening, and the removal of seed coat enchanced these changes. 3. Treated the dormant grains with water solution of gibberellic acid increased the germination, but the same treatment inhibited it (table 6), when the grains had completed their after-ripening. 4. Pre-chilling the soaked grains at 4 ⊥. for 2 days increased the percentage of germination, when they were translocated to 25 ⊥. Determination on the sugar content indicated that both the total and reducing sugar were increased in around 100% than the check. The effect of pre-chilling seems that stimulated the growth of the embryo on the one hand and mobilized the reserve food on the other. 5. During the course of soaking (24 hours), the content of the deoxyribonucleic acid in the embryos of old wheat grains increased 29.4% (2905) and 36% (2419), but not for the grains either shortly after harvested or completed the after-ripening by artificial means.
Abstract (Browse 2272)  |  Full Text PDF       
Developmental Morphology of the Inflorescence of Sorghum vulgare Pers.
Author: Kuo John-shang
Journal of Integrative Plant Biology 1959 8(3)
      
    1. The vegetative shoot apex of koaliang (Sorghum vulgare Pers.) is similar to the other grasses in that it gives rise successively to the leaf primodia and retains its dome form though it increases somewhat in volume following the completion of the vegetative growth. 2. The vegetative shoot apex transforms into the reproductive one when the 11th or 12th leaf is expanding and the shoot apex, being about 80 cm above the ground, increases rapidly in volume but retains its general form. Then the bract primodia appear at the base of the shoot apex and the branch primodia of the first order become noticeable at the axil of the rudimentary bracts. The branch primodia of the second, the third and the fourth order appear in succession. These characteristics are similar to those of the Panicum milliaceum. 3. The differentiation of the inflerescence is basipetal, while the differentiation of spikelet is acropetal. The order of the differentiation is as follows: the outer glume, the inner glume, the lemma of the first flower, the first flower, the lemma of the second flower, the second flower. The order of the development of the flower parts is the palaea, the stamens, the pistil and the lodicules. 4. During the differentiation of the spikerlet at the appearence of the stamens of the second flower, two kinds of spikelets are differentiated: the spikelets with long rachilla begin to degenerate and the sessile spikelets continue to develope normally. There is a difinite ratio between these two spikelets. At the tip of the branches three spikelets are formed, and two of them will degenerate and one will continue to develope normally. On both sides of the branches, only two spikelets are formed and one of them developes and the other degenerates. The degeneration of the spikelets is similar to that of the bristles in millet.
Abstract (Browse 2709)  |  Full Text PDF       
Ten Years of Botany in China
Author: F. H. Wang and R.C. Ching
Journal of Integrative Plant Biology 1959 8(3)
Abstract (Browse 1890)  |  Full Text PDF       
Studies on Plant Respiration. IV. Some Morphological, Physiological and Biochemical Changes During Germination of Rice at Different Partial Pressures of Oxygen
Author: C. Chu and P. S. Tang
Journal of Integrative Plant Biology 1959 8(3)
      
    Morphological, physiological and biochemical changes during germination of rice (var. Yinfang) were studied as function of oxygen tension. Seeds left to germinate on moist quartz-sand fin the dark at 22 ⊥ under 21%, 5% and 0每0.2% oxygen (continuous flow) were taken out for examination on the lst, 5th and the 10th days of germination. The results of the experiments are analyzed and interpreted as follows. 1. The process of germination in rice seeds (var. Yinfang) includes the following three sequential steps none of which may be considered separately a. The elongation of tissues or organs which already possess the full complement of cells prior to soaking. These organs include coleoptile and coleorhyza. This step is characterized by its indifference to oxygen supply. In nitrogen, the coleoptile elongates even faster and for a longer duration than when it is in air. The primary root also elongates under anaerobic conditions but only to the extent limited by cell elongation. The rapid and extensive elongation of the coleoptile in absence of oxygen is here considered as a physiological adaptation which ensures the rice embryo to obtain oxygen needed for completing the other oxygen-requiring steps involved in the entire process of germination. The stomata on the coleoptile, together with the aerenchyma tissues developed later, facilitate oxygen supply from the air above to the organs submerged under the water layer of the flooded seedling bed. The elongation of the coleoptile is here considered only as one of the steps in the entire process of germination, and is not, as considered by some earlier workers, the complete process, nor an "abnormal germination". b. The growth of tissues and organs involving cell division. This includes the growth of leaf and root primordia, of root tips, and formation of branch roots and root hairs. This is strictly an oxygen-dependent step requiring the presence of oxygen, albeit a small amount (less than 2%) for cell division. No cell division occurs in absence of oxygen. In presence of the latter, both cell division and cell elofigation occur. c. Energy and food supply for the germination process. This step involves (1) the digestion of the compound starch grains stored in the endosperm and its mobilization across the scutellum tissue. This forms the main source of food and energy, supply; and (2) the utilization of the small amounts of simple starch grains and protein reserves already present in the scutellum tissue. Step (1) is aerobic, requiring oxygen for enzymic digestion of the starch, while step (2) may proceed under nitrogen. It is possible however, that both steps (1) and (2) are strictly oxygen-dependent, and the disappearance of the small amount of materials in the scutellum tissue itself may be due to oxygen residual in the seeds from the start of the experiment. 2. It may be concluded from the above analysis of the results that germination of rice seeds is an oxygen-requiring process, similar to that of up-land crops such as wheat. When the supply of oxygen is cut off, or seriously reduced, as when seeds are submerged under a layer of water, cell division as well as digestion and mobilization of food reserves are prevented. In such case, although the coleoptile may break the seed coat and elongate the entire process of germination cannot proceed to completion due to failure of the other two oxygen-requiring steps to take place. This conclusion is at variance with the views of some earlier workers who maintain that rice seeds can germinate at the sole expense of energy supplied from fermentation, and when the carbohydrate reserves are exhausted through this inefficient process germination ceases. Our observation that the bulk of the food and energy supply in the endosperm cannot be digested and mobilized during anaerobiosis and the observation that cell division does not occur in absence of oxygen appear to support the views presented in this account. 3. Based on our view that rice germination is an aerobic process it is logical to conclude, as: already pointed out in the first report of this series, that excessive flooding of seedling beds during germination and early growth is not only unnecessary, but undesirable due to depletion of oxygen supply to the embryo. In the light of this conclusion irrigation of rice seedling beds should be conducted with the aim of supplying maximum aeration, while flooding of the beds should be made only as required for temperature regulation and the maintenance of moisture supply necessary for proper water relations of the seedlings. 4. The results and conclusions presented in this account may throw some light on the causes of seedling damages observed in flooded beds. Many factors contribute to the three most commonly observed pathogenic conditions, but from the view point of oxygen supply, the following causes based on depletion of oxygen supply may be offered as a contributing factor to the damage. Excessive flooding of seedling beds seriously reduces oxygen supply to the seedlings. This in turn causes excessive growth of the coleoptile over the coleorhyza. The balance of the seedlings are thus tipped so that roots fail to ground. Under such conditions, the aerotropic tendency of the roots (upward) is stronger than their geotropic tendency so that further growth, if any, of the roots is toward the surface of the water layer. This causes the phenomenon of "topling over". The stoppage of food supply to the partially germinated seedlings due to lack of oxygen causes degeneration of the cells in the elongated organs. This weakens their resistance and prepares the way for infection of the tissues by pathogenic microorganisms such as Achlya, resulting in the "rotting" of the seedlings. Growth and formation of new organs by cell division is an oxygen-requiring process. The inhibition of aerobic respiration by respiratory inhibitors such as azide and fluoride blocks the function of the terminal, oxidases of the cells. This has the same effect as cutting off of oxygen supply. The toxic effect produced on the roots of the seedlings by hydrogen sulfide which is a well known respiratory inhibitor may be explained as due to the inhibition of cell division especially in the root tips, by blocking the activities of terminal oxidases. 5. Finally, based on the results presented in this and the previous accounts of this series of studies on plant respiration, the concept of "multilineal path" and respiration as an adaptive physiological function may be recapitulated in the following words: The adaptation of the plant to its environment is mediated through its changing metabolic patterns which in turn are brought about through the activities of the enzymes within the organism, including the formation and action of adaptive enzymes. The mode, direction and intensities of these enzyme activities vary according to the stages of development in the plant as well as to variations in the environment. The multiplicity of the activities of the enzymes results in varied metabolic patterns which ensure the pliability of adaptation. Variations in the metabolic patterns reflect themselves ultimately in the differences observed in the morphological behavior and physiological performance of the plant as a whole.
Abstract (Browse 2394)  |  Full Text PDF       
Studies on Plant, Respiration. III. lnfluence of Oxygen Tension on Organ Formation, Material and Energy Transformation During Germination of Rice Seeds
Author: P. S. Tang, F. C. Wang and F. C. C. Chih
Journal of Integrative Plant Biology 1959 8(3)
      
    Rice seeds (var. Yinfang) were germinated on moist quartz sand in the dark, at 25每28⊥ for 5 to 10 days. Changes in dry weight, available carbohydrate and heat of combustion in the seeds and organs were investigated under 0每0.2%, 2%, 5%, 8.5% and 20.8% (air) oxygen with continuous streaming gas mixtures. Amounts and efficiencies of material transformation in relation to organ formation in the germinating seeds as well as energy relations were compared under these conditions. With ample oxygen supply (2每20.8%), for each milligram of organ formed approximately another milligram of stored material is left from the embryo in the process so that the efficiency of transformation is about 50%. This efficiency is significantly lowered at 0每0.2% O2 tension. The amounts of materials left from the endosperm and the weight of the organs formed decreased with decreasing oxygen tension. Lowered oxygen tension hinders root formation. At 20.8% O2, the root/top ratio is 1:1, at 2% O2 the ratio becomes ca 1:3. Coleoptile growth is favored under lowered oxygen tention. With insufficient oxygen supply (0每0.2%) loss in dry weight in the endosperm is significantly retarded and very little or no increase in dry weight occurred in the organs. Under such conditions growth is limited to the elongation of the coleoptile. No root formation occurred under such conditions. Since under atmospheric conditions the solubility of oxygen is from 0.7% (at 15 ⊥) to 0.5% (at 30⊥) and since these values are lowered by dissolved substances and by respiration, seeds submerged under flooded seedling beds are surrounded by partial pressures of oxygen of less than 1%, and still more probably it is in the neighborhood of 0.2%. This condition is that which is found in these experiments to be unfavorable for rice seed germination. Of the 25 milligrams of air-dry weight of a rice grain, the hull occupies 4 mg (15%), the embryo weighs only 0.26 mg (1%) and the bulk is made up of the endosperm which comprises 84% (22 mg) of the total weight. Of the 22 mg of endosperm tissue, only 18.5 mg is "available carbohydrate". The extent and efficiency with which this material is used for organ formation is affected by partial pressure of oxygen in the surrounding atmosphere. In air, on the 5th day of germination, 13.75 mg is left of the 18.80 mg of "available carbohydrates'' originally present in the seed; under 5% O2, 14.96 mg is left, and under 0每0.2% O2, 15.58 mg is left. On the 10th day of germination the figures are respectively, 7.48, 8.07 and 11.95 mg. More storage materials are left over at lowered oxygen supply, not less, nor exhausted, as assumed by some earlier workers. The embryo obtains 8 times its own weight of material from the endosperm in 5 days at 20.8% oxygen. On the 10th day, this ratio becomes over 24. This rate of translocation and transformation is lowered with oxygen lack so that under 0--0.2% oxygen, it is only one-eighth of that in air. In presence of oxygen 1.2每2.3 calories of heat is lost for each mg of organ formed. On the basis of energy change measured as heat of combustion, the efficiencies of transformation are: on the 5th day of germination, 67.1% at 20.8% O2; 78% at 5% O2; and 68% at 0每0.2% O2. The values obtained on the 10th day of germination are: 68.5%, 70% and 19% respectively. The heat of combustion per gram of endosperms and seedlings increases during the course of germination, indicating conversion of a part of the material into that with a higher heat content. The changes in heat energy of the seeds as actually measured by calorimetry differs from that calculated from carbohydrate loss. This "residual" energy is considered as due to simultaneous presence, to varying degrees, of aerobic and anaerobic respiration at all oxygen tensions. The possibility of transformation of this residual energy into "energy of organization" is also considered. The results of the experiments presented in this account support our contention that the germination of rice seeds (Yinfang, a lowland variety) is an oxygen requiring process. Although rice seeds, due to possession of a strong alcoholic fermentation system can withstand anaerobic conditions for a few days, for good germination and healthy growth of the seedlings oxygen supply is essential. In presence of oxygen (5每20.8%), material and energy transformation is more efficiently carried out, and organ formation in the embryo and seedlings are such as to meet the demand for healthy seedling culture. These results are also in accord with the concept of "multilineal path" and respiration as an adaptive physiological function of the living plant as postulated in the previous accounts of this series of studies on plant respiration.
Abstract (Browse 1967)  |  Full Text PDF       
Ten Years of Plant Physiology Research in China
Author: P. S. Tang
Journal of Integrative Plant Biology 1959 8(3)
Abstract (Browse 1712)  |  Full Text PDF       
 

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