Jian Feng

Calcium is an essential macronutrient for plant growth and development, and there is an optimal calcium concentration for plant growth. Calcium ion concentration changes create “calcium signals” that regulate plant growth through perception, decoding, transduction, and response processes. However, the mechanisms by which calcium signaling regulates photosynthesis are still not fully understood. In this study, Quercus acutissima seedlings were used to investigate the inhibitory effects of different concentrations of the calcium channel blocker lanthanum chloride (LaCl₃) on photosynthesis and the underlying mechanisms. The results show that increasing LaCl₃ concentration significantly decreased photosynthetic parameters, photosynthetic pigment contents, and photosynthetic product accumulation. Long-term water use efficiency decreased with increasing LaCl₃ concentration, while instantaneous water use efficiency initially increased and then decreased. Structural equation modeling analysis indicated that LaCl₃ concentration was significantly positively correlated with leaf calcium concentration in Quercus acutissima seedlings, while it was significantly negatively correlated with stomatal conductance, carotenoids, and soluble sugar content. The study concludes that LaCl₃ directly inhibits the photosynthetic physiological processes of Quercus acutissima seedlings by blocking calcium signaling, providing insights into the regulatory mechanisms of calcium signaling in plant photosynthesis and a theoretical basis for the cultivation and application of Quercus acutissima under varying environmental conditions.

Age controls a tree’s responses to environmental cues and shading influences tree growth and physiology. These are basic principles of “Afforestation under canopy”, an approach that is widely used in the regeneration of Korean pine forests. Studying the underlying mechanism helps us to understand tree adaptation and utilize it in forest management. In this study, we investigated the transcriptomic changes in the uppermost main stems of the Korean pine tree (Pinus koraiensis, Sieb. et Zucc.) at different ages (5, 7, 10, 14, and 17 years) and in different growth conditions (open-grown and shade-grown trees) using RNA-Seq. In total, 434,005,837 reads were produced and assembled into 111,786 unigenes. After pairwise comparisons, 568 differentially expressed unigenes (DEUs) were identified. The greatest number of DEUs was identified in the comparison between 5-year-old open-grown trees and 17-year-old shade-grown trees, while no DEUs were identified in 15 pairwise comparisons. Among these 568 DEUs, 45 were assigned to gene ontology (GO) terms associated with response to environmental changes, including “response to stress” (26) and “response to light and temperature” (19); 12 were assigned to GO terms associated with sexual reproduction, such as “sexual reproduction”, “specification of floral organ identity”, “pollen tube guidance”, and “fruit ripening”; 15 were heat shock protein genes and showed decreased expression patterns with age; and one, annotated as Pinus tabuliformis DEFICIENS-AGAMOUS-LIKE 1, showed an increased expression pattern with age, independent of the reproductive state or growth conditions of Korean pine trees. Altogether, these findings not only demonstrate the molecular aspects of the developmental and physiological effects of age and shading on Korean pine trees, but also improve our understanding of the basic principles of “Afforestation under canopy”.

The phytohormone auxin controls many aspects of plant development. Auxin/indole-3-acetic acid (Aux/IAA) transcriptional factors are key regulators of auxin responses in plants. To investigate the effects of auxin on gene expression during the rooting process of Larix cuttings, a subtractive cDNA library was constructed and 272 UniEST were obtained by using suppression subtractive hybridization (SSH). Based on a fragment of 272 UniEST, the full-length cDNA of LaIAA2, an Aux /IAA gene fromLarix was isolated. Then, the response expression of LaIAA2 to auxin was determined by treating with different sources and concentration of auxin and cycloheximide and the expression patterns of LaIAA2 were examined in different tissues. The results show that LaIAA2 appears to be the first response gene of auxin and LaIAA2 gene was involved in the root development and auxin signaling. The express pattern of LaIAA2 gene indicated that it might play a central role in root development, specially regulated lateral and adventitious root production. Key words: Aux/IAA gene family, auxin, LaIAA2, Larix

In order to find out the ecological distribution patterns of soil microbes under artificial Eucalyptus grandis stand, the amount and distribution of soil bacteria, fungi and actinomycetes in Hongya County of Sichuan Province were investigated in 2004. The results showed that soil microbial population under Eucalyptus grandis stand varied with seasons, being the maximum in autumn, fewer in spring, and the minimum in summer. The numbers were decreased in order of bacteria > actinomycetes > fungi, which were mainly concentrated in 0-20 cm soil layer, and rapidly decreased with increasing soil depth. In 0-60 cm soil layer, the numbers of aerobic bacteria were 0. 31 x 10(6) - 14.39 x 10(6), actinomycetes were 0.06 x 10(6) - 0.79 x 10(6), fungi were 0.06 x 10(6) - 0.79 x 10(6), and anaerobes were 0.05 x 10(6) - 3.22 x 10(6) CFU x g(-1). Comparing with artificial C. glauca stand and farming land, Eucalyptus grandis stand had a larger number of soil microbes, suggesting that Eucalyptus grandis was benefit for soil microbial activity. The Simpson and Shannon-Wiener index of the physiological groups of bacteria was 0.773 and 1.896, respectively.