Crescimento e anatomia foliar de Cymbidium sp. Cultivadas em diferentes condições de luz / Leaf growth and anatomy of Cymbidium sp. Cultivated in different light conditions

This study attempted to clarify the effects of dark, light and ethylene on plant growth and endogenous levels of indole-3-acetic acid (IAA), cytokinins and abscisic acid in Catasetum fimbriatum. Dark-incubation fully inhibited root and pseudobulb formation as well as leaf growth, but favored shoot elongation. The results of continuous and active growth in dark-incubated shoots (stolons) were induced by strong apical meristem sink activity and by the significantly increased levels of cytokinins in shoots. In fact, shoot length, cytokinin and IAA levels in dark-incubated shoots were about twice as great as for those grown under light conditions. Moreover, the total cytokinin level in shoots of C. fimbriatum under light conditions without ethylene was significantly higher than that found in roots. High levels of cytokinins in dark-grown stolons may be closely related to the absence of roots in C. fimbriatum. Under light conditions, the increased IAA level in shoots is mediated by ethylene. However, ethylene caused a significant increase of cytokinins in roots of light-treated plants, which may be involved in the retardation of root growth. Since the difference of cytokinins in shoots between ethylene-treated and non-treated plants under light conditions is small, it is concluded that the marked inhibition of leaf growth in ethylene-treated plants can be attributed to ethylene. Zeatin and zeatin riboside are the major cytokinins in C. fimbriatum regardless of the light conditions, ethylene treatment or organ types.

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Light regulation of endogenous salicylic acid levels in hypocotyls of Helianthus annuus seedlings

Botany ◽

10.1139/b10-042 ◽

2010 ◽

Vol 88 (7) ◽

pp. 668-674 ◽

Cited By ~ 18

Author(s):

Leonid V. Kurepin ◽

Linda J. Walton ◽

David M. Reid ◽

C. C. Chinnappa

Keyword(s):

Salicylic Acid ◽

Helianthus Annuus ◽

Leaf Growth ◽

Stem Elongation ◽

Light Regulation ◽

Shade Avoidance ◽

Light Conditions ◽

Direct Role ◽

Positive Effects

Plants growing in canopy shade typically exhibit increased stem elongation and reduced leaf growth. This is as a result of direct interactions between plant photoreceptors sensing the change (reduction) in the ratio of red to far-red (R/FR) light and photosynthetically active radiation (PAR) and plant hormones, and regulating these morphological traits. The effect of the varying light conditions found in shade on endogenous salicylic acid (SA) content was tested, and the possible role of SA in shade avoidance by sunflower ( Helianthus annuus L.) hypocotyls was examined. A logarithmic increase in PAR irradiance levels increased endogenous SA levels roughly 10-fold. Separation of individual light wavelengths (R, FR, and blue) constituting the PAR irradiance of sunlight, established that only FR light had significant and positive effects on endogenous SA levels. Further, a low R/FR ratio significantly increased the endogenous SA content in hypocotyls compared with normal and high R/FR ratios. Uncoupling the effect of R/FR ratio and PAR irradiance on endogenous SA content demonstrated that PAR irradiance is a much stronger signal than FR light-enrichment. Thus, while a low R/FR ratio increases the SA content in sunflower hypocotyls, low PAR, the other component of canopy shade, decreases the SA content much more effectively than low R/FR ratio increases it. Therefore, it appears that SA probably has no direct role in shade avoidance effects.

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Growth dynamics and leaf quality of the stinging trees Dendrocnide moroides and Dendrocnide cordifolia (Family Urticaceae) in Australian tropical rainforest: implications for herbivores

Australian Journal of Botany ◽

10.1071/bt98006 ◽

2000 ◽

Vol 48 (2) ◽

pp. 191 ◽

Cited By ~ 7

Author(s):

M. Hurley

Keyword(s):

Leaf Growth ◽

Leaf Age ◽

Growth Dynamics ◽

Light Conditions ◽

Hair Density ◽

Leaf Quality ◽

Young Leaves ◽

Growth Attributes ◽

Changing Light

Leaf growth dynamics and leaf quality of Dendrocnide moroides (Wedd.) and Dendrocnide cordifolia (L.S.Sm.) Jackes and Hurley varied widely with age, season, plant height and habitat. Althoughleaves were produced continuously, growth rates varied seasonally. Leaf moisture and nitrogen content increased in spring and summer and decreased with age, while toughness increased with age. All leaf growth attributes varied with height, with the majority of activity occurring on mid-sized plants. Leafgrowth rates and proportions of different leaf age classes were similar for both species. Leaves were larger and lived longer in shade. Size and longevity responded rapidly to changing light conditions, reflecting their ability to survive in small rainforest gaps. Leaves of all ages were highly nutritious and the exceptionally nutritious young leaves were abundant throughout the year making them susceptible to herbivore attack. However, immature stinging tree leaves were densely covered with painful stinging hairs and hair density decreased with age. Further to causing pain, stinging hairs of D. moroides and D. cordifolia are shed continuously and may deter mammalian herbivores by causing allergic reactions. However, the leaves of stinging trees appeared better suited to the rapid colonisation of rainforest gaps, than in fending off or avoiding herbivore damage.

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LIGHT-STIMULATED LEAF GROWTH ON INTACT AND EXCISED BEAN PLANTS (PHASEOLUS VULGARIS L.). I. CHARACTERIZATION OF BASIC RESPONSES

Israel Journal of Plant Sciences ◽

10.1080/07929978.1999.10676765 ◽

1999 ◽

Vol 47 (3) ◽

pp. 141-145 ◽

Cited By ~ 1

Author(s):

Shimon Lavee ◽

Elizabeth Van Volkenburgh ◽

Robert E. Cleland

Keyword(s):

Phaseolus Vulgaris ◽

Leaf Growth ◽

Red Light ◽

Leaf Expansion ◽

Light Conditions ◽

Whole Plant ◽

Bean Plants ◽

Bright White Light ◽

Root Excision

The effect of root excision on the growth of primary leaves, petioles, and epicotyls of bean plants (Phaseolus vulgaris L.) has been investigated for plants growing in various light conditions. Plants were initially grown in either continuous dim red light (RL; 4 μmol m−2S−1) or bright white light (WL; 100 μmol; m−2S−1, 16 h light: 8 h dark photoperiod) for 10 days. On day 10, some plants were excised. Then, both intact and excised plants were returned to RL or WL, or switched to the other light treatment (RL to WL, WL to RL). Exposure to WL on day 10 promoted leaf expansion and inhibited petiole and epicotyl growth, regardless of light pretreatments before day 10. Root excision reduced leaf expansion by 40–50% both in WL and RL. Petiole and epicotyl growth were less affected. Removal of the cotyledons or the stem apex caused a slight but significant reduction of leaf elongation in both intact and excised plants. Apex removal reduced epicotyl elongation but did not stop it. Although excision of roots partially inhibited leaf and epicotyl development, the relative response of excised plants to the light treatments was similar to that of intact plants. These results justify the use of derooted plants to study leaf growth in a “whole plant” excised system.

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209 Influence of Lettuce Growth with High Temperature and Low Solar Radiation Conditions

HortScience ◽

10.21273/hortsci.35.3.427b ◽

2000 ◽

Vol 35 (3) ◽

pp. 427B-427

Author(s):

Ken-ichiro Yasuba ◽

Shigeki Furuya ◽

Hidekazu Sasaki

Keyword(s):

High Temperature ◽

Solar Radiation ◽

Leaf Growth ◽

Leaf Shape ◽

Total Solar Radiation ◽

Light Conditions ◽

Low Light ◽

Early Autumn ◽

Growth Chambers ◽

Radiation Conditions

When we grow lettuce in the hot season in Japan, lettuce heads sometimes grow abnormally. In early autumn, we frequently find strange shapes of lettuce because of a projecting leaf midrib. Poorly shaped lettuce is unmarketable. We found that lettuce grew abnormally under the high temperature and low solar radiation conditions at the time of 1200 °C accumulative temperature from seeding (average temperature was >20 °C and daily total solar radiation was under 18 MJ/m2). Midribs of both good-shaped (resistance of projecting midrib) and poorly shaped cultivars projected this condition, but the symptom of the former was milder than that of the latter. So, we investigated the difference of leaf growth between good and poorly shaped cultivars using growth chambers. We set up six patterns of environmental conditions, which consisted of three patterns of temperature (30/22 °C, 24/16 °C, and 18/10 °C) and two patterns of light (4 and 2 MJ/m2). The two- to three-leaf seedlings, which were grown in the greenhouse for 27 days after sowing, were transplanted in the 250-mL pots and were carried to growth chambers. We measured width and length of each leaf 9 days after planting. Consequently, the ratio of width to length (w:l) of new leaves became low when we grew lettuce in high temperature or low light conditions. The w:l of good-shaped cultivars were higher than that of poorly shaped cultivars. Good-shaped cultivars did not grow spindly with ease on high temperature and low light conditions, like an early autumn environment. Now we will try to investigate the relationship between leaf shape and head shape on the poorly shaped conditions of some lettuce heads.

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Light Conditions Affect NaCl-Induced Physiological Responses in a Clonal Plant Species Hydrocotyle vulgaris

Proceedings of the Latvian Academy of Sciences Section B Natural Exact and Applied Sciences ◽

10.2478/prolas-2020-0050 ◽

2020 ◽

Vol 74 (5) ◽

pp. 335-343

Author(s):

Ineta Samsone ◽

Una Andersone-Ozola ◽

Andis Karlsons ◽

Gederts Ievinsh

Keyword(s):

Light Intensity ◽

Plant Species ◽

Clonal Growth ◽

Leaf Blade ◽

Leaf Growth ◽

Clonal Plant ◽

Fold Increase ◽

High Light ◽

Light Conditions ◽

Low Light

Abstract In order to understand if differences in light conditions can affect responses of a clonal plant species to increased soil salinity, the long-term effect of two substrate concentrations of NaCl on leaf growth, clonal plasticity and oxidative enzyme (peroxidase and polyphenol oxidase) activity in Hydrocotyle vulgaris L. plants grown at low, moderate and high light conditions was studied. H. vulgaris appeared to be a shade-tolerant species, since both leaf blade and petiole growth was inhibited at low light intensity. At low light intensity, H. vulgaris plants represented characteristics of halophytes with significant stimulation of leaf blade and petiole growth by NaCl, especially at low concentration. Secondary clonal growth was stimulated by increased salinity in low light and, for 25 mM NaCl treatment, even in moderate light. There was more than a five-fold increase of peroxidase activity by 100 mM NaCl treatment in high light conditions, in comparison to two-fold and four-fold increase in low and moderate light, respectively. The existence of different endogenous control mechanisms during H. vulgaris response to light and NaCl at the level of leaf growth, clonal growth and oxidative metabolism could be proposed. The possible ecological meaning of the presented results is discussed in detail.

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