Showing papers on "Plant physiology published in 1980"

Alterations in the physiology of CO2 exchange in tomato plants grown in CO2-enriched atmospheres

Abstract: Young, greenhouse-grown tomato plants were transferred to growth cabinets where they were maintained in normal air (0.03% CO2) or in air enriched to 0.1 or 0.5% CO2. CO2 enrichment increased net as...

Plastid and seedling development in SAN-9789 [4-chloro-5-(methylamine)-2-(α,α,α-trifluoro-m-tolyl)-3-(2H)-pyridasinone]-treated etiolated bean seedlings

Abstract: SAN 9789[4-chloro-5-(methylamine)-2-(α,α,α-trifluoro-m-tolyl)-3-(2H)-pyridasinone] inhibits carotenoid synthesis at the level of phytoene in Phaseolus vulgaris L. Although carotenoids are greatly reduced in the primary leaves, prolamellar bodies and thylakoid membranes are formed containing phototransformable protochlorophyll(ide). SAN 9789 also produces developmental effects similar to those of red light since seedlings treated in darkness are short, show plumular unhooking, formation of adventitious roots, expansion of primary leaves and full expansion of the first trifoliate leaf and first internode. The effect is not directly on phytochrome since far red light does not reverse the effect of SAN. If abscisic acid (ABA) is indeed formed from carotenoids, we may be observing the consequences of reduced levels of ABA leading to reduced ethylene production as occurs with red light. The first trifoliate leaf of SAN-treated plants contains practically no carotenoids (0.2%) compared with untreated 7-day-old, ...

Physiological studies on the ripening of Delaware grapes. II. Effect of the light intensity at the cluster on sugar accumulation and carbon dioxide fixation in the berries under light and dark conditions.

Abstract: The grape berries accumulate sugar very rapidly around 4 weeks before ripening. In order to clarify the mechanism of this sugar accumulation in Delaware grape berries during Stage III, changes in sugar and organic acid content in the growing berries, effects of the number of leaves retained on and time of complete removal of leaves from a bearing shoot on sugar content in the berries, changes in sugar content in the berries detached from the shoot at Stage III, and the conversion of polysaccharides or organic acids into reducing sugars in the berries were investigated.(1) The major sugars in the grape berries were glucose and fructose. These sugars contained totally about 2% in the fresh immature berries, wheras they were about 17% in the mature berries. The ratio of glucose to fructose in the berries changed during the period from bloom to maturity. Glucose in the berries was more predominantly accumulated than fructose during the green color and the early ripening stage of their growth. This relation was reversed at the later ripening stages.(2) As in most fruits, malic acid is present in grape berries. In contrast to them, however, a large amount of tartaric acid contains in the berries, which is the characteristic of this genus. The concentrations of malic acid and tartaric acid in the berries were highest in the beginning of Stage III and the amount of both acids in the berries decreased markedly during the ripening stage, but another peak of tartaric acid concentration was found in the beginning of Stage I.(3) There were no differences in sugar content of the berries on the shoot with 8 leaves or more, as compared to that of the berries on the control shoot, but the berries on the shoot less than 8 leaves had less sugar content. Even the berries on the shoot completely defoliated still accumulated about 6% of reducing sugars.(4) During Stage III, the accumulation of reducing sugars in the berries was found even after complete removal of leaves from the shoot together with girdling at both sides of the node where the cluster was attached.(5) When the enzymes extracted from the berries during Stage III were added into the insoluble substrate prepared from the berries during Stage I, reducing sugar content in the incubation buffer solution increased.(6) When 14C-malic acid was fed into the berries of Stage III through the pedicel for 2 hours in a liquid form, 31% of incorporated 14C was found in the sugar fraction.From these results, it was cleared that the translocation of photosynthates synthesized in the leaves into the berries was most important for the rapid sugar accumulation in grape berries, and also, the translocation of sugars converted from polysaccharides in shoots into the berries and the conversion of polysaccharides and organic acids in the berries themselves into reducing sugars were found to be related to the accumulation as well.

Photosynthesis of young orchid seedlings

Abstract: SUMMARY Adult leaves, protocorms and seedlings of succulent tropical orchids exhibit diurnal fluctuations in acidity. The titratable acidity varied at different stages of growth. The fluctuation in acidity was barely detectable in protocorms but as they grew older, their capacity for acid accumulation increased. The 02 exchange in orchid protocorms and seedlings was similar to that of adult leaves in their responses to temperature, bicarbonate and light intensity. It is concluded that protocorms and seedlings resemble adult organs in having the characteristics of crassulacean acid metabolism (CAM).

Phytochrome control of nitrate reductase activity and anthocyanin synthesis in light-grown sinapis alba (l.). differential responses of cotyledons and hypocotyls

Abstract: Summary In 40 h old cotyledons of etiolated Sinapis alba (L.) red/far-red photoreversibility and the effect of continuous far-red light were used to demonstrate the involvement of phytochrome in the control of in vivo nitrate reductase activity and anthocyanin synthesis. Over a period of several days during the development of S. alba seedlings, in the light, in vivo nitrate reductase activity and anthocyanin synthesis were determined in the cotyledons and hypocotyls. Seedlings were grown under two light environments; fluorescent white light, establishing an estimated phytochrome photo-equilibrium, φE, of 0.69, simulating direct sunlight and fluorescent white light with added far-red light, establishing an estimated phytochrome photo-equilibrium of 0.26, simulating ‘shade’ or ‘canopy’ light. The time courses of both responses were greatly influenced by these different light qualities. Furthermore, in the case of nitrate reductase activity the cotyledons and hypocotyls showed marked differences in their responses to light quality. In the cotyledons a light source establishing a low photo-equilibrium was initially more effective in eliciting the response, but with time, a light source establishing a high photo-equilibrium became the more effective. In the hypocotyls a light source establishing a high photo-equilibrium was always the more effective. The anthocyanin response showed the crossing over of effectiveness of high and low photo-equilibrium in both tissues. The results are discussed in terms of the transition from the ‘high irradiance reaction’ of young seedlings to a possible steady state of phytochrome control in the mature plant.

The effect of indole-3-acetic-acid on the photosynthetic apparatus of Sinapis alba

Abstract: The influence of indole-3-acetic-acid (IAA) during the development of primary leaves of Sinapis alba was studied. IAA treatment (4 ppm ≈ 22.8 μM) caused a decrease of dry weight, soluble reducing sugars, soluble protein, chlorophylls, carotenoids and cytochrome f; it also caused a lower ratio of protein to chlorophyll, a lower ratio of chlorophyll a to chlorophyll b and a higher ratio of chlorophyll per cytochrome f. Furthermore, IAA treatment induced a significantly lower rate of CO2 fixation and a depressed nitrite reductase activity. Similar effects could also be observed in adaptation reactions brought about by red light and low-light (or shade) conditions.

Endogenous Cytokinins in Bougainvillea 'San Diego Red.' III. Effect of Photoperiod and Gibberellic Acid on Flowering and Cytokinin Levels

Abstract: Bougainvillea `San Diego Red' plants, subjected to nine 8-h photoinductive cycles, showed a decrease in endogenous cytokinin levels This decrease occurred in all plant tissues but was least pronounced in the shoot tips, establishing them as the primary site for active nutrient mobilization. The decrease could be correlated with flower development. Application of GA3 to plants growing under short-day conditions reversed the flowering response and caused an increase in endogenous cytokinin levels similar to those detected in vegetative plants grown under long-day conditions. This suggests that gibberellins may play an important role in maintaining Bougainvillea plants in a vegetative state.

Avocado seed germination studies.

Abstract: "Waldin" avocado (Persea americana Mill.) seeds were soaked for 24 hours in concentrations of 0, 250 and 500 ppm gibberellic acid (GA) in lots of 784 seeds each. Moreover, half of the seeds in each lot were left intact and the other half had the apical and basal ends cut off prior to soaking. Cumulative seed germination was re corded 19, 23, 34, 44 and 54 days after planting. Cut seeds at each and all concentraaion(s) of GA snowed higher initial germination than uncut seeds, but the differences dis appeared by 34 days after planting. Cut seeds receiving 250 ppm GA showed higher initial germination, but this differ ence also was eliminated in subsequent measurements. Overall, GA treatment caused no practical differences in total germination. Cutting of seeds reduced total germina tion significantly, probably as a result of embryo damage due to cotyledon separation during cutting, soaking and planting. Nurseries have traditionally experienced problems with avocado propagation caused by a variable germination period of rootstock seeds, which frequently forces the nurseries to extend the propagation period as they wait for late-germinating seedlings to achieve graftable size. The preferred method is to be able to graft everything at one time without having to go back over the propagation beds. Some nurseries cope with this problem by germinating the seeds in seedbeds, then transplanting the seedlings to containers soon after emergence. Thus, propagation can be conducted in sequence on relatively uniform stocks. How ever, the use of a seedbed and transplanting is more labor intensive than seeding directly into containers. Research was initiated in Florida and other areas to enhance the rate of germination of avocado seeds and thus increase seedling uniformity to facilitate once-over propaga tion. Early results indicated that removal of the seed coat of some types of avocados would enhance germination and uniformity (3, 4). However, seed coat removal is difficult and time consuming on many types of avocados and is little used today. Subsequent research showed that cutting off the apical (and sometimes basal) end of the seed facilitated germina tion. Cutting the seed is commonly practiced in avocado propagation today. Work by Leal et al. (4) in Florida centered on the use of gibberellic acid (GA) imbibition of of avocado seeds, with and without the seed coat. 'Waldin' seeds, with and without seed coats, imbibed for 12, 24 and 48 hours in various concentrations of GA, showed enhanced germination and seedling uniformity under laboratory/ greenhouse conditions. Similar results in seedling size and uniformity have been noted in other research with avocados

Abscisic Acid and Other Naturally Occurring Plant Growth Inhibitors

Abstract: Some aspects of the physiological role of naturally occurring plant growth inhibitors have been studied in collaboration between the Institute of Plant Biochemistry, Halle/Saale, the Institute of Plant Physiology, Moscow, and the Institute of Experimental Botany, Prague. These include both the physiological activity and natural occurrence of phenolics in plants [cf. (1–7)] as well as the biochemistry and physiology of ABA metabolism. As an example, the occurrence of ABA and ABA conjugate in bleeding sap, wood, and bark of birch trees will be reported and discussed with respect to their role in breaking dormancy.