Arabidopsis (Arabidopsis thaliana) plants subjected to water deficit, sodium chloride (NaCl), or abscisic acid treatments were shown to exhibit a significant increase in the amount of leaf cuticular lipids. These stress treatments led to increases in cuticular wax amount per unit area of 32% to 80%, due primarily to 29% to 98% increases in wax alkanes. Of these treatments, only water deficit increased the total cutin monomer amount (by 65%), whereas both water deficit and NaCl altered the proportional amounts of cutin monomers. Abscisic acid had little effect on cutin composition. Water deficit, but not NaCl, increased leaf cuticle thickness (by 49%). Electron micrographs revealed that both water-deprived and NaCl-treated plants had elevated osmium accumulation in their cuticles. The abundance of cuticle-associated gene transcripts in leaves was altered by all treatments, including those performed in both pot-grown and in vitro conditions. Notably, the abundance of the ECERIFERUM1 gene transcript, predicted to function in alkane synthesis, was highly induced by all treatments, results consistent with the elevated alkane amounts observed in all treatments. Further, this induction of cuticle lipids was associated with reduced cuticle permeability and may be important for plant acclimation to subsequent water-limited conditions. Taken together, these results show that Arabidopsis provides an excellent model system to study the role of the cuticle in plant response to drought and related stresses, and its associated genetic and cellular regulation.

https://www.jstor.org/stable/pdfplus/40537629.pdf

The impact of water deficiency on leaf cuticle lipids of Arabidopsis.

The special conditions during in vitro culture result in the formation of plantlets of abnormal morphology, anatomy and physiology. After ex vitro transfer, these plantlets might easily be impaired by sudden changes in environmental conditions, and so need a period of acclimatization to correct the abnormalities. This review is focused upon contemporary information on the changes in leaf structure, water relations and photosynthesis during acclimatization of plantlets to ex vitro conditions. It also describes some ways of improving plant survival and for the speeding up of acclimatization.

Acclimatization of Micropropagated Plants to Ex Vitro Conditions

We examined the ability of yellow poplar (
 Liriodendron tulipifera
 ) tissue cultures and plantlets to express modified mercuric reductase (
 merA
 ) gene constructs. Mercury-resistant bacteria express merA
 to convert highly toxic, ionic mercury, Hg(ll), to much less toxic, elemental mercury, Hg(O). Expression of merA
 in transgenic plants might provide an ecologically compatible approach for the remediation of mercury pollution. Because the alteration of the bacterial merA
 gene sequence is necessary for high-level expression in Arabidopsis thaliana
 , yellow poplar proembryogenic masses (PEMs) were transformed with three modified merA
 constructs via microprojectile bombardment. Each construct was synthesized to have altered flanking regions with increasing amounts of modified coding sequence. All merA
 constructs conferred resistance to toxic, ionic mercury in independently transformed PEM colonies. Stability of merA
 transgene expression increased in parallel with the extent of gene coding sequence modification. Regenerated plantlets containing the most modified merA gene (
 merA18
 ) germinated and grew vigorously in media containing normally toxic levels of ionic mercury. The merA18
 plantlets released elemental mercury at approximately 10 times the rate of untransformed plantlets. These results indicate that plants expressing modified merA
 constructs may provide a means for the phytoremediation of mercury pollution.

Development of transgenic yellow poplar for mercury phytoremediation.

Morpho-physiological disorders in in vitro culture of plants

The role of activated charcoal in plant tissue culture.

Embryos of longleaf pine (Pinus palustris Mill.) were induced to form numerous adventitious buds along their cotyledons when placed in culture on chemically defined nutrient media. The buds when excised and transferred to other media form roots and vigorous plantlets. Plantlets were obtained from numerous embryos using three different seed sources. Histological observations describing these patterns of differentiation are presented.

Differentiation of plantlets in Longleaf Pine (Pinus palustris Mill.) tissue cultured in vitro

Leaf anatomy of tissue-cultured liquidambar styraciflua (hamamelidaceae) during acclimatization

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 CO2 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 CO2 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.

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

Somatic embryogenesis in tissue cultures of pecan

The effects of thidiazuron (TDZ) on adventitious bud and shoot formation from hypocotyl segments of sweetgum (Liquidambar styracifiua) were tested alone and in combination with 2,4-dichlorophenoxyacetic acid (2,4-D) The combination of 1 mg/1 TDZ with 001 mg/l 2,4-D resulted in the highest frequency of bud production Lower concentrations of TDZ stimulated shoot production, generating the most shoots at 01 mg/1 TDZ with 001 mg/1 of 2,4-D Inhibition of shoot elongation by TDZ was overcome by transferring shoot cultures to a shoot proliferation medium lacking TDZ or containing naphthaleneacetic acid and benzyladenine in addition to TDZ Shoot production in liquid culture was significantly greater than that in solid culture Comparisons of in vitro and ex vitro rooting of the adventitious shoots demonstrated that ex vitro rooting produced plants with faster growth rates and more extensive root systems

Harry E. Sommer

Papers

Differentiation of plantlets in Longleaf Pine (Pinus palustris Mill.) tissue cultured in vitro

Leaf anatomy of tissue-cultured liquidambar styraciflua (hamamelidaceae) during acclimatization

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

Somatic embryogenesis in tissue cultures of pecan

High-frequency induction of adventitious shoots from hypocotyl segments ofLiquidambar styracifiua L. by thidiazuron.