The role of cotyledons in early development of pine seedlings

1968 ◽  
Vol 46 (10) ◽  
pp. 1173-1183 ◽  
Author(s):  
S. Sasaki ◽  
T. T. Kozlowski
Keyword(s):  
Light Intensity ◽  
Pinus Resinosa ◽  
Dry Weight ◽  
Red Pine ◽  
Partial Reduction ◽  
Low Light ◽  
Pine Seedlings ◽  
Reduced Light ◽  
Proportional Decrease

The role of photosynthetically active cotyledons on development of young red pine (pinus resinosa Ait.) seedlings, and especially on growth of primary needles, was studied over a 30-day period. Photosynthesis of cotyledons, as measured with an infrared CO2 analyzer, was variously reduced by photosynthesis-inhibiting herbicides (atrazine, simazine, propazine, monuron), by reduced light intensity, or by combinations of these. When photosynthesis of cotyledons was completely eliminated shortly after seed germination, the primary needles failed to expand, and dry weight production by seedlings was inhibited. Partial reduction of photosynthesis by herbicides, low light intensity, or both of these was followed by proportional decrease in expansion of primary needles and reduction in dry weight increment of seedlings. Reduced photosynthesis in cotyledons inhibited expansion of primary needles rather than formation of their primordia which occurred early in ontogeny. Growth of cotyledons appeared to utilize carbohydrate reserves to a large extent as cotyledons of many plants emerged even in the dark.

A laboratory study of vertical migration

1955 ◽  
Vol 144 (916) ◽  
pp. 329-354 ◽  
Keyword(s):  
Light Intensity ◽  
Vertical Migration ◽  
Time Course ◽  
Tap Water ◽  
Low Light ◽  
Overhead Light ◽  
Light Intensities ◽  
Orientation Response ◽  
Reduced Light ◽  
Characteristic Maximum

In a tank filled with a suspension of indian ink in tap water, a population of Daphnia magna will undergo a complete cycle of vertical migration when an overhead light source is cycli­cally varied in intensity. A ‘dawn rise’ to the surface at low intensity is followed by the descent of the animals to a characteristic maximum depth. The animals rise to the surface again as the light decreases, and finally show a typical midnight sinking. The light intensities at the level of the animals in this experiment are of the same order as those which have been reported in field observations; the time course of the movement also repeats the natural conditions in the field. The process is independent of the duration of the cycle and is related only to the variation in overhead light intensity. At low light intensity the movement of the animal is determined solely by positive photo-kinesis; the dawn rise is a manifestation of this, and is independent of the direction of the light. At high light intensities there is an orientation response which is superimposed upon an alternating positive (photokinetic) phase and a negative phase during which movement is inhibited. The fully oriented animal shows a special type of positive and negative phototaxis, moving towards the light at reduced light intensities and away from it when the light intensity is increased. In this condition it follows a zone of optimum light intensity with some exactness. Experiments show that an animal in this fully oriented condition will respond to the slow changes of intensity characteristic of the diurnal cycle, while being little affected by tran­sient changes of considerable magnitude.

scholarly journals Leaf Characteristics and Yield Performance of Mungbean (Vigna radiata L.) Varieties under Different Levels of Shading

2018 ◽  
Vol 15 (2) ◽  
pp. 40-51
Author(s):  
M A Hossain ◽  
M A Hasan ◽  
S Sikder ◽  
A K M M B Chowdhury
Keyword(s):  
Light Intensity ◽  
Grain Yield ◽  
Vigna Radiata ◽  
Dry Weight ◽  
Light Levels ◽  
Spongy Layer ◽  
Partial Shade ◽  
Shade Condition ◽  
Reduced Light ◽  
Leaf Dry Weight

An experiment was carried out to evaluate the leaf characteristics and yield performances of mungbean (Vigna radiata L.) under different light levels at the Crop Physiology and Ecology Research Field of Hajee Mohammad Danesh Science and Technology University, Dinajpur during March to June 2016. The experiment was laid out in a split plot design with three replications. Three light levels (L100 - 100 % light intensity, L75- 75 % light intensity and L50- 50% light intensity) were assigned in the main plots and four varieties (BARl Mung-6, BINA Mung-8, BINA Mung-5 and BU Mug-4) were assigned in subplots. Mosquito nets of different pore size were used for maintaining 75 and 50 percent light intensity. Leaf area was increased due to reduced light levels in all mugbean varieties but the increment was significant in BINA Mung-5 and BINA Mung-8 only at 75% light intensity at 40 days after sowing and only in BARI Mung-6 with L50 and BU Mug-4 with L75 and L50at 50 days after sowing. Due to reduced light levels, leaf dry weight was affected more in BINA Mung-5 and BU Mug- 4 than BARI Mung-6 and BINA Mung-8. Leaf thickness was reduced under shade in all the mungbean varieties, except in BU Mug-4 at 75% light intensity, and the reduction in leaf thickness was mainly due to the reduction in thickness of spongy layer. The palisade layer thickness was influenced insignificantly but spongy layer thickness was increased in BINA Mung-5 at 100% light intensity. The grain yields (t ha-1) of BARI Mung-6 and BINA Mung-8 remained stable under partial shade condition but the grain yield of BINA Mung-5 and BU Mug-4 was reduced drastically under partial shade condition. Higher leaf dry weight, number of pods plant-1, seeds pod-1, and heavier grains in BARI Mung-6 and BINA Mung-8 contributed to the higher grain yield plant-1 under partial shade condition than in BINA Mung-5 and BU Mug-4.The Agriculturists 2017; 15(2) 40-51

Effect of low light intensity at night on cow traffic in automatic milking systems

2014 ◽  
Vol 54 (10) ◽  
pp. 1784
Author(s):  
Fanny Hjalmarsson ◽  
Ingemar Olsson ◽  
Sabine Ferneborg ◽  
Sigrid Agenäs ◽  
Emma Ternman
Keyword(s):  
Light Intensity ◽  
Dairy Cows ◽  
Milk Yield ◽  
Negative Impact ◽  
Night Time ◽  
Low Light ◽  
Milking Frequency ◽  
Automatic Milking ◽  
Automatic Milking Systems ◽  
Reduced Light

Several studies have shown benefits of long-day (16 h) photoperiod in lactating dairy cows, but have not identified a suitable light intensity for the dark hours. It is known that the locomotion pattern of dairy cows is altered at low light intensities and this may translate to reduced cow traffic and milking frequency, which would have a negative impact on system productivity. However, it is also recognised that a significant disturbance of rest may have a negative impact on the health and productivity of high-yielding dairy cows. This study examined the effect of three different night-time light intensities (LOW: 11 ± 3, MED: 33 ± 1 and HIGH: 74 ± 6 lx) on number of gate passages, milking frequency and milk yield in dairy cows in automatic milking systems. The study was conducted in Sweden during the winter of 2012–13 and the treatments were applied in a crossover design to three herds with an automatic milking system. Minimum day time light intensity was 158 lx. Data on gate passages, milking frequency and milk yield for 172 ± 49 (mean ± s.d.) cows during the last 22 days of each 34-day study period were analysed for treatment differences and differences in daily distribution over 24 h, during day time and night time. Light intensity did not affect total number of gate passages per 24-h period and cow, but number of gate passages per hour and cow was in all treatments lower during night time than during day time. Milking frequency was increased in MED compared with both HIGH and LOW (P < 0.05). Milk yield decreased with reduced light intensity, and differed significantly between HIGH and LOW treatments, 45 ± 1 kg and 44 ± 1 kg, respectively (P < 0.001). Our conclusion is that reducing light intensity to 11 lx at night time does not affect cows’ general activity as gate passages remained the same for all treatments. However, milk yield decreased with reduced light intensity, which might be related to a lower feed intake. We argue that providing night light for dairy cows, as required by many welfare acts, might be related to production level rather than welfare aspects and that the recommendations should be revised.

The role of cotyledons in growth and development of woody angiosperms

1974 ◽  
Vol 52 (1) ◽  
pp. 239-245 ◽  
Author(s):  
P. E. Marshall ◽  
T. T. Kozlowski
Keyword(s):  
Light Intensity ◽  
Seedling Emergence ◽  
Robinia Pseudoacacia ◽  
Dry Weight ◽  
Weight Increase ◽  
Betula Alleghaniensis ◽  
Ulmus Americana ◽  
Weight Increment ◽  
Stems And Leaves

The role of photosynthetically active cotyledons in the growth of young woody angiosperm seedlings was studied over a 35-day period under controlled environmental conditions. Two experiments were performed. In the first, cotyledons of Robinia pseudoacacia, Ulmus americana, and Ailanthus altissima were removed or covered at 7, 14, or 21 days after seedling emergence. In the second experiment, seedlings of Robinia pseudoacacia, Betula alleghaniensis, and Acer saccharum were grown over a range of light intensities. Removing or covering Robinia cotyledons of seedlings of any age resulted in lower dry weights of roots and stems than in controls. Removing or covering cotyledons of only 7-day-old Robinia seedlings retarded dry weight increase of foliage. Robinia seedling heights were unaffected by cotyledon covering or removal. Covering Ulmus americana cotyledons had no significant effect on dry weight increment of stems or foliage or on seedling height. Removal of Ulmus cotyledons from 7-day-old seedlings inhibited dry weight increase of roots, stems, and leaves and inhibited height growth. Removal of Ailanthus cotyledons inhibited dry weight increment of roots, stems, and leaves more than did covering of cotyledons. Species varied greatly in cotyledon development and response to light intensity. Cotyledon size was affected by light intensity in Robinia, but not in Betula or Acer. Responses of cotyledons to light intensity differed from those of foliage leaves. Cotyledon photosynthesis appeared to have a very important role in seedling growth in Robinia and Ailanthus and a less important role in Ulmus.

Morphological acclimation to light intensity in Douglas-fir seedlings

1977 ◽  
Vol 55 (15) ◽  
pp. 2033-2042 ◽  
Author(s):  
Allan P. Drew ◽  
William K. Ferrell
Keyword(s):  
Light Intensity ◽  
Root Growth ◽  
Dry Weight ◽  
Frost Damage ◽  
Douglas Fir ◽  
Stem Length ◽  
Low Light ◽  
Spring Frost ◽  
Terminal Bud ◽  
Leaf Surface Area

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown outdoors under 9, 44, and 100% light intensity and were sampled periodically over their first growing season for stem, leaf, and root dry weights, and the data were analyzed allometrically. In addition, seedlings were assessed for number of needles per stem length, ratio leaf surface area: leaf dry weight, and maximum seedling dry weight. The experiment was repeated during a 2nd, warmer, year.Maximum growth occurred under partial shade and moderate temperatures. In the 1st year, seedlings allocated progressively more dry matter to shoot than to root growth as light intensity decreased. In the 2nd year, root growth was favored at the expense of shoot growth. In both years, shoot structural alterations were such as to favor enhanced photosynthesis under low light. Acclimative changes are explained in terms of an interaction between light, temperature, and seedling size.A second experiment showed that seedlings grown under low light set a terminal bud sooner in the fall and broke bud sooner the next spring than seedlings preconditioned to high light. They also suffered more spring frost damage and showed greater incidence of lammas growth in the 2nd year. No effect of 1st-year preconditioning on timing of budbreak was evident in the 3rd year.

Growth and water relations of black locust and pine seedlings exposed to controlled water stress

1983 ◽  
Vol 13 (2) ◽  
pp. 334-338 ◽  
Author(s):  
Paul J. Schulte ◽  
Paul E. Marshall
Keyword(s):  
Polyethylene Glycol ◽  
Water Stress ◽  
Surface Area ◽  
Black Locust ◽  
Dry Weight ◽  
Growth Conditions ◽  
Red Pine ◽  
Polyethylene Glycol 4000 ◽  
Xylem Pressure ◽  
Pine Seedlings

Some responses of very young jack pine (Pinusbanksiana Lamb.), red pine (Pinusresinosa Ait.), and black locust (Robiniapseudoacacia L.) seedlings grown under constant water stress conditions induced by polyethylene glycol 4000 culture solutions were investigated. Seedlings grown under stressful conditions had lower leaf conductance, produced less foliar surface area, and accumulated less dry weight than nonstressed seedlings. Seedlings grown under nonstressed conditions were found to undergo considerable transpiration at night. When compared with the pines, black locust seedlings grew more rapidly, had lower (more negative) xylem pressure potentials, and showed poorer survival under the more stressful growth conditions.

Growth kinetics of Marquis wheat. II. Carbon dioxide dependence

1972 ◽  
Vol 50 (4) ◽  
pp. 883-889 ◽  
Author(s):  
F. D. H. Macdowall
Keyword(s):  
Carbon Dioxide ◽  
Light Intensity ◽  
Carbon Dioxide Concentration ◽  
Dry Weight ◽  
Maximum Growth ◽  
Carbon Dioxide Enrichment ◽  
Low Light ◽  
Growth Coefficient ◽  
Light Intensities ◽  
Wide Range

Marquis wheat was grown in growth rooms with four different concentrations of carbon dioxide and four to seven different intensities of light in a 16-h photoperiod at 25 °C. Growth was expressed quantitatively as the pseudo-first-order rate coefficient. Carbon dioxide stimulated growth, but the effect was greater the lower the light intensity in opposition to the known effect on photosynthesis. Carbon dioxide and light, in effect, did not influence the "rate" of growth of wheat additively but, rather, mutually compensated over a wide range. The growth coefficient of the roots was a little less than that of the shoots at all carbon dioxide concentrations and light intensities, probably owing to the cost of translocation. However, root growth benefited most from carbon dioxide enrichment at low light intensities. At intermediate light intensity there appeared to be a carbon dioxide concentration optimal for shoot growth. Carbon dioxide enrichment did not influence the maximum growth coefficient of Marquis wheat with respect to light intensity. The light-using efficiency of growth, calculated for vanishingly low light intensity at which it is maximal, was maximal for shoots at 1300 ppm CO2 but that for laminal area and root dry weight increased with CO2 to 2200 ppm at which the value for "leaves" was nearly fourfold that for roots. Unlike photosynthesis, the stimulation of growth by raised CO2 concentration was accomplished by increased efficiency of, and not capacity for, the net photosynthetic use of light.

scholarly journals Light Intensity Affects Growth, Photosynthetic Capability, and Total Flavonoid Accumulation of Anoectochilus Plants

HortScience ◽  
2010 ◽  
Vol 45 (6) ◽  
pp. 863-867 ◽  
Author(s):  
Zengqiang Ma ◽  
Shishang Li ◽  
Meijun Zhang ◽  
Shihao Jiang ◽  
Yulan Xiao
Keyword(s):  
Light Intensity ◽  
Chlorophyll Concentration ◽  
Dry Weight ◽  
Total Flavonoid ◽  
Stem Length ◽  
Photon Flux ◽  
Low Light ◽  
Four Levels ◽  
Anoectochilus Formosanus ◽  
Flavonoid Accumulation

Anoectochilus formosanus, a medicinal plant used to treat hypertension, lung disease, and liver disease, was grown to maximize biomass and secondary metabolite production in a controlled environment under four levels of photosynthetic photon flux (PPF), namely, 10, 30, 60, or 90 μmol·m−2·s−1, that is L10, L30, L60, and L90 treatments, respectively. On Day 45, all growth values were greatest for the L30 plants. Dry weight was lowest for the L10 plants. Leaf area, stem length, and fresh weight were lowest for the L90 plants. The chlorophyll concentration was highest in the L10 treatment and decreased with increasing PPF. Electron transport ratios of leaves were highest in the L30 treatment and lowest in the L90 for the second leaf (counted down from the apex) and in the L10 for the third leaf. An increase in light intensity from 10 to 60 μmol·m−2·s−1 increased the superoxide dismutase activity and was associated with an increase in the total flavonoid concentration. The total flavonoid concentration (mg·g−1 DW) was greatest in the L60 and lowest in the L90. However, the total flavonoid content (mg/plant) was highest in the L30 plants as a result of great biomass. The results indicated that A. formosanus is a typical shade plant suitable to grow under low light intensity at PPF of 30 to 50 μmol·m−2·s−1 for both growth and production of total flavonoid. A light intensity of 90 μmol·m−2·s−1 induced stress on plant growth and reduced photosynthetic capability and the flavonoid accumulation.

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