Chlorophyll In Seedlings Research Articles

The Responses of Four Typical Annual Desert Species to Drought and Mixed Growth

Soil desiccation is increasingly threatening the growth of vegetation in artificial forests at the margins of arid desert oases, where a variety of annual herbaceous plants coexist. It is important to understand the response of annual desert plants to droughts and mixed growth and the resulting patterns of change in photosynthetic and physiological properties. Our results showed that annual plants were primarily affected by drought stress, and the effect of interspecific competition was significant only under severe drought stress. In the sprouting stage, moderate drought increased seed germination rates, whereas severe drought stress decreased the germination rates. In the growth phase, the aboveground and belowground parts of annual herbaceous plants showed a synergistic response to drought. Under mild and moderate drought stress, annual herbaceous plants promoted photosynthesis by increasing chlorophyll content, thereby promoting plant stem growth. Following moderate and high drought, root vigor increased to maintain basic metabolic activities and annual herbaceous plants used the “shadow and avoid” response by increasing stem and root length to increase competitive ability. Under severe drought stress, planted seedling chlorophyll levels decreased, resulting in a simultaneous reduction in photosynthetic ability. The root growth of annual herbaceous plants depends on their photosynthesis ability but the decrease in biomass led to a decrease in root growth. The mixed habitat reduced the inhibition of seedling stem growth by drought stress and promoted plant growth.

Seed germination and in vitro propagation of three threatened endemic South African Aloe species

Aloe modesta Reynolds (endangered), A. peglerae Schönland (critically endangered), and A. reitzii Reynolds (vulnerable) are endemic South African Aloe species valued for their horticultural and/or medicinal value, appearing on the Red List of South African Plants. Propagation is an important step in the cultivation of these species for their conservation. This study examined the effect of temperature (15, 20, 25, and 30°C) and photoperiod (constant dark, 16 h light, and constant light) on seed germination of these three species. The in vitro propagation of A. reitzii was also investigated by examining the effect of different cytokinins [kinetin, 6-benzyladenine (BA), meta-topolin (mT), and meta-topolin riboside (mTR)] on shoot multiplication. Germination percentage and mean germination rate of A. modesta were significantly inhibited when the seeds were incubated at a low temperature (15°C) in comparison to incubation at other temperatures (20 – 30°C). An increase in temperature significantly decreased mean germination time (MGT), as well as increased seedling chlorophyll and carotenoid contents in A. peglerae and A. reitzii. A reduction in germination speed, evident in increased MGT was observed in the three species when seeds were incubated under constant light and 16 h light as compared to constant dark. Medium with 5.0 µM meta-topolin produced the highest A. reitzii shoot proliferation (16 shoots) per shoot-tip explant after eight weeks of culture. This shoot multiplication rate translates to a potential production of 1 118 481 shoots per shoot-tip explant per annum, based on a geometric progression with six possible multiplication cycles per annum. Aloe reitzii shoots produced from BA and kinetin treatments had a high flavonoid content whereas all mT and mTR treatments gave reduced flavonoid content. Seed and/or in vitro propagation protocols of these threatened endemic Aloe species established in this study can be employed in the biodiversity conservation of Aloe species for their sustainable use.

Improving the Predictive Value of Phytochrome Photoequilibrium: Consideration of Spectral Distortion Within a Leaf.

The ratio of active phytochrome (Pfr) to total phytochrome (Pr + Pfr), called phytochrome photo-equilibrium (PPE; also called phytochrome photostationary state, PSS) has been used to explain shade avoidance responses in both natural and controlled environments. PPE is commonly estimated using measurements of the spectral photon distribution (SPD) above the canopy and photoconversion coefficients. This approach has effectively predicted morphological responses when only red and far-red (FR) photon fluxes have varied, but controlled environment research often utilizes unique ratios of wavelengths so a more rigorous evaluation of the predictive ability of PPE on morphology is warranted. Estimations of PPE have rarely incorporated the optical effects of spectral distortion within a leaf caused by pigment absorbance and photon scattering. We studied stem elongation rate in the model plant cucumber under diverse spectral backgrounds over a range of one to 45% FR (total photon flux density, 400–750 nm, of 400 μmol m–2 s–1) and found that PPE was not predictive when blue and green varied. Preferential absorption of red and blue photons by chlorophyll results in an SPD that is relatively enriched in green and FR at the phytochrome molecule within a cell. This can be described by spectral distortion functions for specific layers of a leaf. Multiplying the photoconversion coefficients by these distortion functions yields photoconversion weighting factors that predict phytochrome conversion at the site of photon perception within leaf tissue. Incorporating spectral distortion improved the predictive value of PPE when phytochrome was assumed to be homogeneously distributed within the whole leaf. In a supporting study, the herbicide norflurazon was used to remove chlorophyll in seedlings. Using distortion functions unique to either green or white cotyledons, we came to the same conclusions as with whole plants in the longer-term study. Leaves of most species have similar spectral absorbance so this approach for predicting PPE should be broadly applicable. We provide a table of the photoconversion weighting factors. Our analysis indicates that the simple, intuitive ratio of FR (700–750 nm) to total photon flux (far-red fraction) is also a reliable predictor of morphological responses like stem length.

Cd胁迫下SA和NO互作对小麦幼苗根生长和叶绿素含量的影响

以"陇春27"号水培小麦幼苗为研究材料，外源添加水杨酸（SA）、一氧化氮（NO）清除剂（carboxy-PTIO，c-PTIO）、NO供体硝普钠（SNP）、硝酸还原酶（NR）抑制剂钨酸盐（Tungstate）及NO合成酶（NOS）抑制剂（L-NAME）进行不同预处理，分析其在镉（Cd）胁迫下根的生长和叶片叶绿素含量的变化，探讨SA和NO互作对小麦幼苗Cd胁迫的缓解机制。结果表明：随着Cd处理时间的延长，小麦幼苗根中SA含量显著降低，NO含量则呈现先增加（6 h和12 h）后减少（24 h和48 h）的趋势；Cd胁迫抑制了小麦幼苗根的生长，减少了叶片叶绿素的含量，而一定浓度的SA或SNP预处理可以缓解Cd胁迫对小麦幼苗根长的抑制作用，增加叶绿素的含量。c-PTIO、L-NAME和Tungstate单独预处理显著抑制了小麦幼苗根的生长，减少了NO的含量，但不影响叶绿素含量。SA400+L-NAME预处理可以缓解Cd胁迫对小麦幼苗根长的抑制作用以及叶绿素和NO含量的减少作用；SA400+c-PTIO或SA400+Tungstate预处理可增加Cd胁迫下叶绿素的含量，但对根的伸长无影响。进一步研究发现，Cd胁迫抑制了NR的活性，而SA400预处理可以使Cd胁迫下NR的活性增强，不同处理对NOS的活性均无影响。综上所述，Cd胁迫导致小麦幼苗根内源SA含量降低和NO含量先升高再降低；外源添加SA或SNP预处理缓解了Cd胁迫对根生长的抑制和叶绿素含量降低的作用；外源SA通过影响NO的产生从而提高小麦幼苗对Cd胁迫的耐受性，最终缓解了Cd对小麦幼苗的毒害作用。;Soil pollution of heavy metals is very severe in China, especially the cadmium pollution. Excessive cadmium not only causes severe damage to the growth and development of plants, leading to disorders of their physiological functions, reduced photosynthesis, and reduced organic matter accumulation and so on, but also greatly endangers human health. In this research, the growth of roots and the content of chlorophyll in the seedlings of wheat (Triticum aestivum L. cv. Longchun 27) were analyzed after being pretreated with exogenous salicylic acid (SA), nitric oxide (NO) scavenger (Carboxy-PTIO, c-PTIO), NO donor sodium nitratol (SNP), nitrate reductase (NR) inhibitor (Tungstate), NO synthase inhibitor (L-NAME) and then being treated with 100 μmol/L CdCl₂, to explore the mitigation mechanism of SA and NO interaction on Cd-induced phytotoxicity. The results showed that with the prolongation of cadmium treatment time, the content of SA decreased gradually, when the treatment time was extended to 24h, the SA content no longer changed, but the content of NO increased firstly (6 h and 12 h), then decreased (24 h and 48 h) in the roots of wheat seedlings. Cd stress significantly inhibited the root growth and reduced the chlorophyll content of the leaves. However, pretreatment with suitable SA or SNP could moderate the inhibition of Cd stress on the growth of roots and increase the content of chlorophyll in wheat seedlings. The single pretreatment of c-PTIO, L-NAME and Tungstate restrained the growth of roots significantly and reduced the content of NO, but had little effect on the content of chlorophyll. The pretreatment of SA400+L-NAME could alleviate the inhibition of root elongation and the reduction of chlorophyll as well as NO content in wheat seedlings were induced by Cd stress; the pretreatment SA400+c-PTIO or SA400+Tungstate could augment the content of chlorophyll, but there was no effect on root elongation under Cd stress. Further studies showed that Cd stress significantly weaken NR activity, while the pretreatment of SA400 could increase the NR activity of wheat seedlings roots under Cd stress; NOS activity was not affected by different treatments. In summary, Cd stress caused the decrease of endogenous SA content and the first increase of NO content and then decrease of wheat seedlings; the pretreatment with exogenous SA or SNP reduced the inhibition of root growth and the decrease of chlorophyll content by Cd stress; exogenous SA improved the tolerance of wheat seedlings to Cd stress by affecting the production of NO, ultimately, the phytotoxic effects of Cd on wheat seedlings were alleviated.

Proteomic analysis of wheat seeds produced under different nitrogen levels before and after germination

The objective of this study was to investigate differentially abundant proteins (DAPs) of wheat seeds produced under two nitrogen levels (0 and 240 kg/ha) before and after germination. We selected samples at 8 and 72 h after imbibition (HAI) to identify DAPs by iTRAQ. The results showed 190 and 124 DAPs at 8 and 72 HAI, respectively. Alpha-gliadin and chlorophyll a-b binding protein showed the biggest difference in abundance before and after germination. In GO enrichment analysis, the most significantly enriched GO term was nutrient reservoir activity at 8 HAI and endopeptidase inhibitor activity at 72 HAI. Moreover, many DAPs involved in mobilization of stored nutrients and photosynthesis were mapped to KEGG pathways. Dough development time, dough stability time and seedling chlorophyll content under N240 were significantly higher than those under N0, which validated the results of proteomic analysis. These results are crucial for food nutrition and food processing.

ROS Produced via BsRBOHD Plays an Important Role in Low Temperature-Induced Anthocyanin Biosynthesis in Begonia semperflorens

Low temperature (LT) is an important elicitor that triggers anthocyanin biosynthesis. To investigate whether the reactive oxygen species (ROS) produced via RBOH are involved in this process, we analysed the function and mechanism of ROS produced via RBOH during LT-induced anthocyanin biosynthesis in Begonia semperflorens Link & Otto. The results showed that BsRBOHD transcription was upregulated in LT-grown seedlings at the 3rd hour, which was followed by the upregulation of anthocyanin-biosynthesis genes at the 5–9th hour, leading to anthocyanin accumulation on the 2nd day. The LT-induced increases in ROS production, BsRBOHD and anthocyanin-biosynthesis gene transcription, and anthocyanin content were abolished by the pre-treatment of seedlings with DPI [an inhibitor of nicotinamide adenine nucleoside phosphorylase (NADPH) oxidase or DMTU (a H2O2 scavenger)], but were promoted by pre-treatment with NADPH (a substrate of NADPH oxidase). Changes in the chlorophyll fluorescence parameters showed that pre-treatment of DPI or DMTU alleviated the LT-induced decrease in the seedling chlorophyll content and a/b ratio, which subsequently alleviated the LT-induced decreases in the ABS/CSm, TRo/CSm, RC/CSm, ETo/CSm and REo/CSm values. In contrast, NAPDH pre-treatment intensified these changes. Therefore, we suggest that ROS produced via BsRBOHD may be involved in the LT-induced anthocyanin biosynthesis by strengthening the overaccumulation of ROS produced by the overexcitation of PSII reaction centres and overflux from $${\text{Q}}_{{\text{A}}}^{ - }$$ to NADP+ in B. semperflorens.

Exogenous jasmonic acid and humic acid increased salinity tolerance of sorghum

AbstractSalinity limits germination and plant growth and development in 45 million ha worldwide. Techniques to overcome this problem are needed. This project investigated the effects of jasmonic acid (JA) (0, 5, and 10 mM JA) and humic acid (HA) (0, 3, and 6 g HA kg−1 soil) on growth and physiological parameters of forage sorghum (Sorghum bicolor L. Moench) under different NaCl salinity levels (0, 100, and 200 mM NaCl, with an equivalent electrical conductivity (EC) of 0.12 dSm−1 as control treatment, 3.22, and 5.78 dSm−1, respectively). NaCl salinity reduced emergence percentage, emergence rate, salt tolerance index and seedling vigor index, all seedling growth parameters, ascorbate peroxidase (APX) activity, chlorophyll a, b and total chlorophyll content. Proline content and soluble protein content were increased with salinity. At the 200 mM salinity level, seeds treated with 10 mM JA had a positive effect on emergence percentage, emergence rate, shoot length, total fresh weight, salt tolerance index, seedling vigor index, chlorophyll a and total chlorophyll content. At 200 mM NaCl salinity level, seeds treated with 6 g HA kg−1 soil had increased root length, total dry weight, salt tolerance index, seedling vigor index, shoot length, protein content, APX, chlorophyll b, and total chlorophyll in seedlings. The application of 5 mM JA combined with 6 g HA kg−1 soil was most effective in minimizing salinity stress. Our study suggested that the appropriate combined application of HA and JA could efficiently protect early seedlings from salt stress damage and alleviate abiotic stress.

AtPep3 is a hormone-like peptide that plays a role in the salinity stress tolerance of plants

Peptides encoded by small coding genes play an important role in plant development, acting in a similar manner as phytohormones. Few hormone-like peptides, however, have been shown to play a role in abiotic stress tolerance. In the current study, 17 Arabidopsis genes coding for small peptides were found to be up-regulated in response to salinity stress. To identify peptides leading salinity stress tolerance, we generated transgenic Arabidopsis plants overexpressing these small coding genes and assessed survivability and root growth under salinity stress conditions. Results indicated that 4 of the 17 overexpressed genes increased salinity stress tolerance. Further studies focused on AtPROPEP3, which was the most highly up-regulated gene under salinity stress. Treatment of plants with synthetic peptides encoded by AtPROPEP3 revealed that a C-terminal peptide fragment (AtPep3) inhibited the salt-induced bleaching of chlorophyll in seedlings. Conversely, knockdown AtPROPEP3 transgenic plants exhibited a hypersensitive phenotype under salinity stress, which was complemented by the AtPep3 peptide. This functional AtPep3 peptide region overlaps with an AtPep3 elicitor peptide that is related to the immune response of plants. Functional analyses with a receptor mutant of AtPep3 revealed that AtPep3 was recognized by the PEPR1 receptor and that it functions to increase salinity stress tolerance in plants. Collectively, these data indicate that AtPep3 plays a significant role in both salinity stress tolerance and immune response in Arabidopsis.

Irrigation and Zn fertilizer management improves Zn phyto‐availability in various rice production systems

AbstractZinc (Zn) is an important micronutrient for rice (Oryza sativa L.) production and its deficiency has been observed in various production systems. High grain Zn concentration is equally important for high rice yield and human health. In this work, the effects of Zn fertilization on seedling growth, grain yield, grain Zn concentration, and their association with root traits were studied under alternate wetting and drying (AWD), aerobic rice (AR), system of rice intensification (SRI), and continuous flooding (CF). Zinc fertilization (15 kg ha−1) improved nursery seedlings chlorophyll and Zn concentrations, root length, and number of roots with highest values observed in CF. At harvesting, maximum plant height, panicle length, total and panicle bearing tillers, and kernel yield were found with Zn addition in AWD and CF rice systems. Mid season drainage provided at maximum tillering and Zn fertilization increased its concentration in leaves, culms, panicles, and grains under CF and AR at physiological maturity. Most of Zn applied was allocated into culms and panicles, nevertheless, a significant increase in grain Zn concentration was also observed in all production systems. Association of leaf Zn with grain Zn concentration was stronger than with culm and panicle Zn. The results indicate that Zn application after rice nursery transplanting is more important for grain Zn enrichment in all rice systems than for increase in grain yield in all systems except AWD where grain yield was also increased. More grain yield in CF and AWD as compared to SRI and AR can also be attributed to decreased spikelet sterility and to better Zn phyto‐availability in these rice systems at physiological maturity.

Interplay between Light and Plant Hormones in the Control of Arabidopsis Seedling Chlorophyll Biosynthesis.

Chlorophyll biosynthesis is one of the most important cellular processes and is essential for plant photosynthesis. After germination under the soil, dark-grown seedlings are etiolated and accumulate the chlorophyll precursor protochlorophyllide (Pchlide) in cotyledons. Upon exposure to light, Pchlide is rapidly converted to chlorophyll to initiate photoautotrophic growth. In this light-regulated de-etiolation process, multiple endogenous phytohormones are also involved. Although the co-regulation of seedling greening by light and hormones has long been observed, recent studies greatly advanced our understanding of their interplay by identifying the key components connecting these pathways. The integrators, such as PHYTOCHROME-INTERACTING FACTORs, ELONGATED HYPOCOTYL 5, ETHYLENE INSENSTIVE 3 and DELLA proteins, are key transcription regulators in light or hormone signaling pathways. This review focuses on these integrators and illustrates the regulatory networks of light and hormone interactions in chlorophyll biosynthesis.

The effects of petroleum-contaminated soil on photosynthesis of Amorpha fruticosa seedlings

A pot experiment was conducted to monitor the dynamic response of photosynthesis of Amorpha fruticosa seedlings to different concentrations of petroleum-contaminated soils from April to September. The results showed that the photosynthetic rates, stomatal conductance and transpiration rate of seedlings significantly decreased in 5–20 g kg−1 petroleum-contaminated soil during the three given sampling period of July 31 (early), August 30 (mid-term) and September 29 (late). However, the intercellular CO2 concentration significantly increased in 10 g kg−1 contaminated soil, while declined in 20 g kg−1 contaminated soil during the early sampling period as well as in 20 g kg−1 contaminated soil during the late sampling period. The leaf relative water content of seedlings significantly increased in 20 g kg−1 contaminated soil during the early sampling period, while it dropped dramatically in 15–20 g kg−1 contaminated soil during the late sampling period. The contents of chlorophyll a, chlorophyll b and the total chlorophyll of seedlings showed a sharp decline during the three sampling periods in contaminated soil. Comprehensively, considering the negative effects of petroleum on the photosynthesis, growth performance and remediation effect on petroleum of A. fruticosa seedlings, this plant was tolerant of petroleum-contaminated soil and was potentially useful for the phytoremediation of petroleum-contaminated sites in northern Shaanxi, China.

Research on Biological Materials for the Preferred of the Chlorophyll Content Gray GM (1,1) Prediction Models Based on the Different Light

Light is one of the most important factor in the growth of plants, with the advent and application of biological materials such as different artificial LED source, the new agricultural technology has been rapid development. In this study, first established the gray GM (1,1) prediction model of the pepper seedlings chlorophyll changes under the different light and then compared of the chlorophyll models under the different light. Last the study found that different artificial LED have the different effect and the forecasting curve and prediction model under the blue is optimal for pepper seedling by comparing the chlorophyll curves and predictive models of pepper seedlings under different light, so blue light is the most suitable for the growth of pepper seedlings. The results turned out that accuracy test of the three gray prediction models can achieve the best grade, and the three gray prediction models have the good practical value. Grey prediction theory can be better applied to the study of the plants.

Effect of Application Uniconazole on the Growth and Physiological Activity of Wheat Seedling

Effects of various azole olefinic on growth and development of wheat were studied under solution-culture conditions. The results showed that moderate azole olefinic can improve the wheat seedling chlorophyll content, and improve the growth of root, restrain the growth of stem. And azole olefinic can reduce the MDA content of the leaf and roots, which can increase the proline content and improve the wheat seedling resistance.

Ectopic expression of different cytokinin-regulated transcription factor genes of Arabidopsis thaliana alters plant growth and development

The plant hormone cytokinin rapidly alters the steady state transcript levels of a number of transcription factor genes suggesting that these might have a function in mediating cytokinin effects. Here we report the analysis of Arabidopsis thaliana plants with an altered expression level of four different cytokinin-regulated transcription factor genes. These include GATA22 (also known as CGA1/ GNL), two genes coding for members of the homeodomain zip (HD zip) class II transcription factor family ( HAT4, HAT22), and bHLH64. Ectopic expression of the GATA22 gene induced the development of chloroplasts in root tissue where it is normally suppressed and led to the formation of shorter and less branched roots. Overexpression of HAT22 lowered the seedlings chlorophyll content and caused an earlier onset of leaf senescence. Enhanced expression of the HAT4 gene led to severe defects in inflorescence stem development and to a decrease in root growth and branching, while hat4 insertional mutants developed a larger root system. 35S:bHLH64 transgenic plants showed a pleiotropic phenotype, consisting of larger rosettes, reduced chlorophyll content and an elongated and thickened hypocotyl. Flower development was strongly disturbed leading to sterile plants. The results are consistent with specific functions of these transcription factor genes in regulating part of the cytokinin activities and suggest their action as convergence point with other signalling pathways, particularly those of gibberellin and light.

How Hormonal Priming of Aged and Nonaged Seeds of Bromegrass Affects Seedling Physiological Characters

Effects of hormonal priming by cytokinin (CK), auxin, and gibberellin (GA) at 0, 25, 50, and 100 ppm of aged and nonaged seeds of bromegrass (Bromus inermis) on some physiological properties of seedlings were evaluated in a pot experiment. The seeds were subjected to accelerated aging to produce aged seeds. Percentage and rate of seedling emergence, seedling vigor, seedling-growth rate (SGR), seedling dry weight, chlorophyll and activity of catalase and peroxidase of seedling decreased following accelerated aging. Auxin priming improved emergence, vigor, SGR, root length, shoot, and seedling height. CK produced largest leaf area, whereas GA-primed seed had the highest concentration of chlorophyll in seedlings. Results suggested that physiological quality of bromegrass seed, especially aged seed, could be improved by hormonal priming. Auxin had the most positive effect on percent emergence, rate of emergence and SGR; CK and GA had positive effects on chlorophyll and leaf area. The three phytohormones in ap...

Hydrogen sulfide counteracts chlorophyll loss in sweetpotato seedling leaves and alleviates oxidative damage against osmotic stress

In this paper, effect of NaHS, a hydrogen sulfide (H2S) donor on chlorophyll and antioxidant metabolism in seedling leaves of sweetpotato under osmotic stress was investigated. With the enhancement of osmotic stress, which was mimicked by PEG-6000, chlorophyll in seedling leaves of sweetpotato (Ipomoea batatas) decreased dramatically. At 15% PEG (w/v), chlorophyll concentration reached only 50% compared with that of the controls. The osmotic-induced decrease in chlorophyll concentration could be alleviated by spraying exogenous H2S donor, NaHS in a dose-dependent manner, while little visible symptoms were observed in leaves sprayed with NaHS under control conditions. It was also shown that H2S or HS− rather than other sulfur-containing components derived from NaHS contributed to the protective role against chlorophyll degradation during osmotic stress. Further studies showed that NaHS spraying dramatically promoted the activities of superoxide dismutase, catalase, ascorbate peroxidase and decreased that of lipoxygenase and the concentrations of hydrogen peroxide (H2O2) and malondialdehyde. In addition, concentrations of endogenous H2S in NaHS-sprayed seedlings were higher than that in water-spraying control under osmotic stress. These data indicated that H2S plays a protective role in sweetpotato seedlings during osmotic stress.

Boron amelioration of aluminum toxicity in mungbean seedlings

Boron (B) amelioration of aluminum (Al) toxicity was studied for growth of mungbean (Phaseolus aureus Roxb.) seedlings and cuttings (without roots) in a growth chamber. Mungbean seedlings and cuttings were grown in the solution with combinations of three concentrations of B (0,5, and 50 μM) and three concentrations of Al (0, 2, and 5 mM) in randomized complete block design experiments for 16 days. Results showed that B significantly promoted elongation of epicotyls and hypocotyls, and increased height of seedlings grown under Al stress. Boron also increased fresh weight of seedlings in high Al solution. Treatment of plants grown with high B and Al stress had no apparent effect on fresh and dry weights of seedling roots. Seedling dry weight increased significantly by adding high B to solutions with 2 mM or 5 mM Al. No significant differences were observed between the high B treatment and the control (normal B, 5 μM) in lengths of epicotyls and fresh and dry weights of mungbean cuttings grown under Al stress. High concentrations of B decreased soluble protein and increased chlorophyll in seedlings treated with 2 mM Al. Boron had no amelioration effect on cuttings grown with Al, although Al increased soluble protein. Our results suggested that B alleviation of Al toxicity was related to root function and Al toxicity may possibly be due, in part, to B deficiency.

Effects of Quantum Flux Density on Photosynthesis and Chloroplast Ultrastructure in Tissue-Cultured Plantlets and Seedlings of Liquidambar styraciflua L. towards Improved Acclimatization and Field Survival

Liquidambar styraciflua L. seedlings and tissue-cultured plantlets were grown under high, medium, or low (315, 155, or 50 microeinsteins per square meter per second photosynthetically active radiation) quantum flux densities. Net photosynthesis, chlorophyll content, and chloroplast ultrastructure of leaves differentiated from these conditions were investigated. Seedling photosynthetic rates at light saturation were positively related to light pretreatments, being 6.44, 4.73, and 2.75 milligrams CO(2) per square decimeter per hour for high, medium, and low light, respectively. Cultured plantlets under all light conditions had appreciably higher photosynthetic rates than noncultured seedlings; corresponding rates were 12.14, 13.55, and 11.36 milligrams CO(2) per square decimeter per hour. Chlorophyll in seedlings and plantlets was significantly higher in low light-treated plants. Seedling leaves had chloroplasts with abundant starch regardless of light pretreatment. In high light, starch granules were predominant and associated with disrupted granal structure. Low light seedling chloroplasts had smaller starch grains and well-formed grana. In contrast, tissue culture-differentiated leaves were devoid of starch; grana were well organized in higher quantum flux density treatments, but disorganized at low flux densities.

Fitness of Heterozygotes in Barley1

The level of dominance at four loci for reproductive fitness was investigated in barley (Hordeum vulgare L,.). Each of the four loci contained a recessive allele, believed to be of spontaneous origin, that is a seedling chlorophyll lethal when homozygous. Populations were established with initial gene frequency of p = .5, and the proportion of normal green to defective seedlings was ascertained in successive selfed generations. Reproductive fitness of the normal homozygote vs the normal heterozygote was indicated in the rate of elimination of the defective allele.The rate of elimination of the defective allele in ‘Colsess I,’ Colsess II,' ‘Xantha 3,’ and ‘Albino 7’ indicated approximately equal fitness of the normal homozygote and heterozygote, thus suggesting a complete dominance interpretation for reproductive fitness. Small deviations from the dominance model in the direction of partial dominance or over‐dominance were about equally frequent for the Colsess I, Xantha 3, and Albino 7 loci. The allele in Colsess II, decreased in frequency at a rate slightly slower than predicted by the dominance model; however, if over‐dominance was present, it was modest. These data, which support a dominance explanation for reproductive fitness, are in conflict with findings on chlorophyll lethals in corn (Zea mays L.) and with reports on heterozygote advantage for agricultural fitness at the Xantha 3 and Albino 7 loci.

Genetic Linkage in Soybeans: Linkage Group I1

Genetic linkage of three genes in soybeans—y12, a seedling chlorophyll deficiency gene, t, a pubescence color gene, and e1, a gene conditioning earliness and shortness—was established in Linkage Group I. The combined recombination value for y12 and el was 20.2 ± 1.1%, for e1 and t was 3.9 ± 0.4%, and for y12 and t was 21.6 — 0.7%. Pubescence color, Tt, and a duplicate locus conditioning cotyledon color, D2d2, previously reported linked, were shown to be inherited independently. The order of genes in Linkage Group I appears to be y12‐e1‐t.