We investigated the effect of growth irradiance (I) on photon-saturated photosynthetic rate (Pmax), dark respiration rate (RD), carboxylation efficiency (CE), and leaf mass per unit area (LMA) in seedlings of the following four tropical tree species with contrasting shade-tolerance. Anthocephalus chinensis (Rubiaceae) and Linociera insignis (Oleaceae) are light-demanding, Barringtonia macrostachya (Lecythidaceae) and Calophyllum polyanthum (Clusiaceae) are shade-tolerant. Their seedlings were pot-planted under shading nets with 8, 25, and 50 % daylight for five months. With increase of I, all species displayed the trends of increases of LMA, photosynthetic saturation irradiance, and chlorophyll-based Pmax, and decreases of chlorophyll (Chl) content on both area and mass bases, and mass-based Pmax, RD, and CE. The area-based Pmax and CE increased with I for the light-demanders only. Three of the four species significantly increased Chl-based CE with I. This indicated the increase of nitrogen (N) allocation to carboxylation enzyme relative to Chl with I. Compared to the two shade-tolerants, under the same I, the two light-demanders had greater area- and Chl-based Pmax, photosynthetic saturation irradiance, lower Chl content per unit area, and greater plasticity in LMA and area- or Chl-based Pmax. Our results support the hypothesis that light-demanding species is more plastic in leaf morphology and physiology than shade-tolerant species, and acclimation to I of tropical seedlings is more associated with leaf morphological adjustment relative to physiology. Leaf nitrogen partitioning between photosynthetic enzymes and Chl also play a role in the acclimation to I. and Y.-L. Feng, K.-F. Cao, J.-L. Zhang.
Australian carnivorous pitcher plant Cephalotus follicularis Labill. produces two types of leaves. During the spring time, the plant produces a foliage type of noncarnivorous leaf called lamina. Later, the second type of leaf is produced - carnivorous pitcher. Using simultaneous measurements of gas exchange and chlorophyll (Chl) fluorescence photosynthetic efficiency of these two distinct forms of leaves were compared. In addition stomatal density, an important component of gas exchange, and Chl concentration were also determined. Pitcher trap had lower net photosynthetic rate
(PN) in comparison to noncarnivorous lamina, whereas the rate of respiration (RD) was not significantly different. This was in accordance with lower stomatal density and Chl concentration in the pitcher trap. On the other hand maximum quantum yield of PSII (Fv/Fm) and effective quantum yield of photochemical energy conversion in PSII (ΦPSII) was not significantly different. Nonphotochemical quenching (NPQ) was significantly higher in the lamina at higher irradiance. These data are in accordance with hypothesis that changing the leaf shape in carnivorous plants to make it a better trap generally makes it less efficient at photosynthesis. However, the pitcher of Cephalotus had much higher PN than it was expected from the data set of the genus Nepenthes. Because it is not possible to optimize for contrasting function such as photosynthesis and carnivory, it is hypothesized that Cephalotus pitchers are less elaborated for carnivorous function than the pitchers of Nepenthes. and A. Pavlovič.
The leaves of 29-d-old plants of Brassica juncea Czern & Coss cv. Varuna were sprayed with 10-6 or 10-8 M aqueous solutions of indole-3-yl-acetic acid (IAA) or its substituted derivatives 4-Cl-IAA, 7-Cl-IAA, and 4,7-Cl2-IAA. All the auxins improved the vegetative growth and seed yield at harvest compared with those sprayed with de-ionised water (control). 4-Cl-IAA was most prominent in its effect, generating 21.6, 39.7, 61.0, 35.0, 65.5, and 56.2% higher values for dry mass, leaf chlorophyll content, carbonic anhydrase (E.C. 4.2.1.1) and nitrate reductase (E.C. 1.6.6.1) activities, net photosynthetic rate, and carboxylation efficiency, respectively, in 60-d-old plants. It also enhanced the seed yield by 31.1% over the control. The order of response of the plants to various auxins was 4-Cl IAA ≥ 7-Cl IAA > 4,7-Cl2 IAA = IAA > control.
Morphological, anatomical and physiological frond traits of Cheilanthes persica (Bory) Mett. ex Kuhn were studied to analyze its adaptive strategy. Mean frond life span is about 340 d. Mature fronds are characterized by 91 g m-2 areal dry mass (ADM) and 217 g m-2 succulence. The reduction of frond water content in July (dehydration phase) caused a 51 % decrease in frond surface area (SA). Fronds were dry in August (desiccation phase); nevertheless, in September they showed an increased SA (rehydration phase). Chlorophyll (Chl) a/b ratio, above 3, and the well developed palisade parenchyma (two layers, total thickness of 103.9 µm) are typical for sun leaves. Chl and carotenoid contents and net photosynthetic rate (PN) increased during frond development until the highest values in April-May (maturity phase). When mean air temperature reached 31.3 °C, stomatal conductance (gs) decreased by 34 % and PN by 33 %. The high pigment contents can dissipate the excess of radiant energy, particularly under unfavourable conditions, when PN is low. Rather high PN was found during the rehydration stage. The pronounced decline of mesophyll activity during the declining phase was confirmed by the lowest PN. and L. Gratani, M. F. Crescente, G. Rossi.
Surface sterilised seeds of mungbean (Vigna radiata L. Wilczek cv. T-44) were soaked in 0, 10-8, 10-6, or 10-4 M aqueous solution of 28-homobrassinolide (HBR) for 4, 8, or 12 h. The treated seeds were grown in sandy loam soil filled in earthen pots and sampled at 30, 40, and 50 d. Net photosynthetic rate, leaf chlorophyll content, carbonic anhydrase activity (E.C. 4.2.1.1), carboxylation efficiency, stomatal conductance, and seed yield at harvest were enhanced by the HBR treatment. The best combination was the pre-sowing seed treatment with 10-6 M HBR for 8 h. and Q. Fariduddin, A. Ahmad, S. Hayat.
Net photosynthetic rate (PN) of Valeriana jatamansi plants, grown under nylon net shade or under different tree canopies, was saturated with photons at 1 000 μmol m-2 s-1 photosynthetic photon-flux-density (PPFD), whereas open-grown plants were able to photosynthesise even at higher PPFD, e.g. of 2 000 μmol m-2 s-1. Plants grown under net shade had higher total chlorophyll (Chl) content per unit area of leaf surface. However, Chl a/b ratio was maximal in open-grown plants, but remained unchanged in plants grown in nylon net shade and under different tree canopies. Sun-grown plants had thicker leaves (higher leaf mass per leaf area unit), higher wax content, and higher PN than shade grown plants. Thus V. jatamansi is able to acclimate to high PPFD and therefore this Himalayan species may be cultivated in open habitat to meet the ever-increasing industrial demand. and S. K. Vats, S. Pandey, P. K. Nagar.
In mature and young leaves of sunflower (Helianthus annuus L. cv. Catissol-01) plants grown in the greenhouse, photosynthetic rate, stomatal conductance, and transpiration rate declined during water stress independently of leaf age and recovered after 24-h rehydration. The intercellular CO2 concentration, chlorophyll (Chl) content, and photochemical activity were not affected by water stress. However, non-photochemical quenching increased in mature stressed leaves. Rehydration recovered the levels of non-photochemical quenching and increased the Fv/Fm in young leaves. Drought did not alter the total Chl content. However, the accumulation of proline under drought was dependent on leaf age: higher content of proline was found in young leaves. After 24 h of rehydration the content of proline returned to the same contents as in control plants. and I. Cechin ... [et al.].
Seedlings of Chrysanthemum, cultivar 'Puma Sunny', were grown under a range of shading regimes (natural full sunlight, 55, 25, and 15% of full sunlight) for 18 days. Here, we characterized effects of varying light regimes on plant morphology, photosynthesis, chlorophyll fluorescence, anatomical traits, and chloroplast ultrastructure. We showed that leaf color was yellowish-green under full sunlight. Leaf area, internode length, and petiole length of plants were the largest under 15% irradiance. Net photosynthetic rate, water-use efficiency, PSII quantum efficiency, and starch grain were reduced with decreasing irradiance from 100 to 15%. Heavy shading resulted in the partial closure of PSII reaction centers and the CO₂ assimilation was restricted. The results showed the leaves of plants were thinner under 25 and 15% irradiance with loose palisade tissue and irregularly arranged spongy mesophyll cells, while the plants grown under full sunlight showed the most compact leaf palisade parenchyma. Irradiance lesser than 25% of full sunlight reduced carbon assimilation and led to limited plant growth. Approximately 55% irradiance was suggested to be the optimal for Chrysanthemum morifolium., S. Han, S. M. Chen, A. P. Song, R. X. Liu, H. Y. Li, J. F. Jiang, F. D. Chen., and Obsahuje bibliografii
Net photosynthetic rate (PN) was high in genotypes with 'C' genome both in the nucleus and cytoplasm. This may be attributed to the co-ordinated manner of acting of both genome sources. Leaf mass per area (LMA) and chlorophyll content increased with leaf nitrogen (N) content but did not show any correlation with PN. The factors which affected PN had the same effect on photosynthetic nitrogen use efficiency (pNUE). Thus, differential allocation of N to the various components influences plant pNUE which is not significantly affected by genome constitution. and A. Anand, K. Suresh, T. V. R. Nair.
A yellow leaf colouration mutant (named ycm) generated from rice T-DNA insertion lines was identified with less grana lamellae and low thylakoid membrane protein contents. At weak irradiance [50 µmol(photon) m-2 s-1], chlorophyll (Chl) contents of ycm were ≈20 % of those of WT and Chl a/b ratios were 3-fold that of wild type (WT). The leaf of ycm showed lower values in the actual photosystem 2 (PS2) efficiency (ΦPS2), photochemical quenching (qP), and the efficiency of excitation capture by open PS2 centres 1 (Fv'/Fm') than those of WT, except no difference in the maximal efficiency of PS2 photochemistry (Fv/Fm). With progress in irradiance [100 and 200 µmol(photon) m-2 s-1], there was a change in the photosynthetic pigment stoichiometry. In ycm, the increase of total Chl contents and the decrease in Chl a/b ratio were observed. ΦPS2, qP, and Fv'/Fm' of ycm increased gradually along with the increase of irradiance but still much less than in WT. The increase of xanthophyll ratio [(Z+A)/(V+A+Z)] associated with non-photochemical quenching (qN) was found in ycm which suggested that ycm dissipated excess energy through the turnover of xanthophylls. No significant differences in pigment composition were observed in WT under various irradiances, except Chl a/b ratio that gradually decreased. Hence the ycm mutant developed much more tardily than WT, which was caused by low photon energy utilization independent of irradiance. and Q. Chen ... [et al.].