Longer Daylength Research Articles

The Effect of Several Amino Acids and some Inorganic Nitrogen Sources on the Growth of Drosera rotundifolia in Long- and Short-Day Conditions

Summary The nitrogen metabolism of a carnivorous plant, Drosera rotundifolia L., has been studied in long-day (18 h light) and short-day (12 h light) conditions in aseptic culture. Growth was clearly weaker in short-day conditions but the responses to the nitrogen sources were about the same in the two daylengths. Organic nitrogen was not necessary for flowering in long-day lengths and none of the amino acids induced flowering in short-day lengths. NH 4 NO 3 (1.25 raM) was utilized more effectively than NH 4 Cl (2.5 mM). D. rotundifolia is not more tolerant towards amino acids than other vascular plants. Only arginine was used nearly as effectively as 4 NO 3 (2.5 mM). Aspartic and glutamic acids gave only weak growth. Most of the amino acids tested were not used when given as the only nitrogen source (proline, hydroxyproline, valine, methionine, leucine, isoleucine, lysine and alanine). A low concentration (0.1 mM) of hydroxyproline inhibited the utilization of NH 4 + ions but interfered less with the utilization of NO 3 - ions and very little with that of arginine.

Growth and development of soyabean cv. TK5 as affected by tropical daylengths, day/night temperatures and nitrogen nutrition

SUMMARYTwo experiments were done in Saxcil growth cabinets in order to investigate the effects of climatic factors and nitrogen nutrition on the growth, reproductive development and seed yield of soyabean cv. TK5. In the first, plants were grown to maturity in eight environments comprising all combinations of two short daylengths (11 h 40 min and 13 h 20 min), two day (27 and 33oC) and two night (19 and 24oC) temperatures. In the second, day temperature was kept at 33oC but the night temperature was varied (19 and 24oC) as was the mineral nitrogen supply (20 and 197 ppm N) to plants which were either inoculated or not with an effective single strain of Rhizobium.Taller, more branched, later flowering plants were produced in the longer daylength but seed yield was hardly affected because the components of yield did not all respond similarly. In the higher day temperature treatments seed yield per plant was reduced by half because all yield components were adversely affected ‐ pods per plant by 34 %, mean seed dry weight by 24 % and seeds per pod just slightly. There was a marked effect of the higher night temperature which promoted early vegetative growth, induced early flowering and although the number of pods per plant was, overall, reduced by 48 %, seed yield per plant was little affected as mean seed dry weight was increased by 37 % and the number of seeds per pod was also increased slightly.Prior to flowering, nodulated plants obtained about two thirds of their total nitrogen requirement via direct uptake and one third through the symbiotic system. Vegetative dry weight and plant nitrogen content were increased by the higher mineral nitrogen level and, although height was slightly diminished, more branches were produced. Seed yield, however, was only slightly increased.These experiments have shown that night temperature is an environmental factor of major importance for the growth of this soyabean cultivar. They have provided, also, a more rational basis for interpreting seasonal variations in growth and seed yield of soyabean in the tropics where, clearly, day and night temperature effects can override those of daylength and nitrogen nutrition.

Studies on the Control of Flower Bud Formation by Temperature and Daylength in Rice Plants : IX. Aging Effect in Relation to Photoperiodic Induction

The aged rice plants produced their flower bud primordia by fewer short-day treatments and under longer day-length as compared to the young plants. On the other hand, the floral initiation of the plants showing high intensity in the vigour of vegetative growth was delayed than that of the plants showing low intensity, although both the plants were sown on the same date. From these facts, it is inferred that aging effect on floral induction is due to the decrease in the vigour of vegetative growth during the course of development.

Growth and Development of Alfalfa Plant under Controlled Environment : I. The effects of daylength and temperature on the growth and chemical composition

Propagated plants of a clone of Du Puits alfalfa were grown for six weeks under combined environments of three photoperiods (8 hr, 12 hr and 16 hr) and four temperature regimes (30°C day 25°C night, 25-20, 20-15, ahd 15-10°C). 1) Long day and warmer temperatures promoted elongation of shoot with longer mean internode and with upright growth habit. Leaf expansion rate increased with increased temperature, but branching ability (b)/c)) decreased as temperature increased, except under long day where it was little affected by temperature (table 1). 2) Under 16hr photoperiod flowering was decreased as temperature decreased, although no flower opened at both 20-15°C and 15-10°C. Under 12 hr photoperiod only one of 5 plants flowered at 30-25°C, none at other temperatures. Under short day no plant formed flower bud at any temperature (table 2). 3) Dry weights of tops, roots and total plant were a little affected by photoperiod. Production of tops increased a little as temperature raised except at 30-25°C where it decreased. Roots weight, on the contrary, increased with decrease of temperature except at 15-10°C where it was small. The weight of whole plant was greatest at 25-20°C, followed by 20-15°C, 30-25°C, then by 15-10°C (fig. 4, 5). 4) Leaf/stem ratio and root/total ratio increased under shorter photoperiods and lower temperatures, while dry matter production of whole plant was little affected by daylength (tab1e 3). Nodule weight per unit top weight increased with decrease of daylength and temmperature, and that per unit root weight also increased with decrease of temperature (fig. 1). 5) Crude protein concentration (CP) of tops increased with decrease of temperature, being little effected by photoperiod. CP of roots and TAC concentration (TAC) of all plant parts were variable under longer photoperiods probably due to difference of plant in matulity stage caused by differential temperatures. Under shortday condition, however, TAC of all parts increased with decrease of temperature (fig. 2). Alcohol-soluble non-protein N % and its ratio to total N% were lower under 16 hr photoperiod as compared with those of shorter daylengths, being increased with decrease of temperature (table 4). 6) It may be a significant fact in view of the regrowth after cutting that plants receiving short days and cooler temperatures accumulated relatively greater amount of TAC and CP in the roots than did plants under longer daylength and higher temperatures (fig. 3, 4).

Effect of artificial shading on growth and morphogenesis of <i>rauvolfia serpentina</i> benth. Ex. Kurz and <i>r. Tetraphylla</i> L.

Context: Plants behaviour is greatly influenced by light intensity, quality and photoperiods. Rauvolfia serpentina Benth. ex. Kurz and R. tetraphylla L. grow well during April to September with longer daylength and maximum light intensity. Growth of both the species continues during rest months with slow rate. From their overall performance in their normal habitat R. serpentina seems to appear that it can tolerate some shading as against R. tetraphylla. Objective: To study the growth behaviour of R. serpentina and R. tetraphylla under three different light intensities i.e. full open sun, partial shade and shade in a glasshouse. Materials and Methods: Experiments were done on three light regimes measured with the help of luxmeter, i.e. full light under natural condition with 100% light under netted cloth cover with 90% and diffused light under muslin cloth with 70% Seedlings were raised in earthenware pots. The harvesting was started after 2 weeks after transference of the plants to their appropriate light intensities. The performance of species was judged with respect to mean dry weight accumulation, leaf area increase, relative growth rate, leaf area ratio, specific leaf area, leaf weight ratio, net assimilation rate and α. Results: In both species dry weight and leaf area increased steadily in successive harvests but R. serpentina and R. tetraphylla appear to behave differently in their response to different light regimes. R. serpentina grows well in partial shade and full light as against R. tetraphylla which does well in full light than in partial shade. R. serpentina always maintained an edge over R. tetraphylla. Conclusion: Both species showed the value of α more than one in most regimes. It means that they are morphogenetically well balanced and are ready for flowering. Keywords: Artificial shading; Growth; Morphogenesis; Rauvolfia serpentine; R. tetraphylla. DOI: http://dx.doi.org/10.3329/jbs.v18i0.8770 JBS 2010; 18(0): 21-26

Influence of Photoperiod on Growth of Green Sunfish, Lepomis cyanellus

Four 6-week experiments were conducted to evaluate the effect of photoperiod on growth (total length and weight), food consumption, and food conversion efficiency by green sunfish. Fish were held at constant temperatures in light-tight aquaria under four photoperiods (8-hr constant; 16-hr constant; variable, increasing from 8 to 16 hr; and variable, decreasing from 16 to 8 hr).Growth, food consumption, and food conversion efficiency were all influenced by photoperiod. Food consumption varied directly with the amount of light to which fish were exposed. Fish growth and food conversion efficiency were closely correlated and were generally highest in the increasing, lowest in the decreasing, and intermediate in the two constant photoperiods, but higher in the longer daylength. The results suggest that photoperiod influences growth through increasing conversion efficiency and also possibly through stimulating food consumption.Varying daylength exerts a greater influence on fish growth than a constant daylength. Increasing photoperiod stimulates growth and decreasing photoperiod inhibits growth. This result suggests that the lack of growth of warmwater fish in fall when water temperatures and average daylength correspond to those of spring is largely due to the influence of decreasing daylength.

LIFE-HISTORY AND PHOTOPERIODIC RESPONSES OF NYMPHS OF TETRAGONEURIA CYNOSURA (SAY)

1. Most nymphs of Tetragoneuria cynosura required one year for the completion of nymphal development in nature. Rapid growth occurred in the summer months and by the end of October, the final instar was attained which served as an overwintering diapause stage; emergence occurred in early April and May. A small percentage of the population (5-10%) exhibited growth retardation and had a lifecyle of two years. These individuals spent the first winter in stages short of the last, the summer in the penultimate stage, and the second winter in the last stage.2. Striking differences occurred in seasonal response to photoperiods of 11 and 14 hours. Durations of the final instar for nymphs collected in August and September were much greater on the longer day-length. Following the fall equinox period, a reversal in response occurred, with the longer photoperiod inducing more rapid development in fall and winter collections. Differences in rates of response became progressively less as time of emergence approached. These results were utilized in an attempt to explain the role of photoperiod in controlling seasonal nymphal development in this species.3. The threshold light intensity necessary to elicit a photoperiodic response was found to be extremely low, probably below 0.002 lux. More than eight, but less than twenty, long-day cycles were necessary to induce irreversibly a response similar to that of the long-day controls.

Some Responses of Alfalfa (Medicago Sativa L.) to Different Lengths of Day and Growth Regulators in the Greenhouse1

SynopsisAlfalfa plants grown under 14 hours of light were more vigorous in growth, had larger leaves and longer internodes, and were taller than those grown under 12 hours. Flowering of plants was profuse in the longer daylength, but was sparse, if present at all, under shortday conditions. Spraying with different growth‐regulators altered the heights of plants, length of internodes, and flowering response. Formative effects were also evident from treatment with certain of the chemicals.