Correction: Transcriptional and physiological analyses of reduced density in apple provide insight into the regulation involved in photosynthesis.

[This corrects the article DOI: 10.1371/journal.pone.0239737.].

Transcriptional and physiological analyses of reduced density in apple provide insight into the regulation involved in photosynthesis.

Different densities have a great influence on the physiological process and growth of orchard plants. Exploring the molecular basis and revealing key candidate genes for different densities management of orchard has great significance for production capacity improvement. In this study, transcriptome sequencing of apple trees was carried out at three different sampling heights to determine gene expression patterns under high density(HD) and low density(LD) and the physiological indices were measured to determine the effect of density change on plants. As a result, physiological indexes showed that the content of Chlorophyll, ACC, RUBP and PEP in the LD was apparently higher than that in control group(high density, HD). While the content of PPO and AO in the LD was noticeably lower than that in the HD. There were 3808 differentially expressed genes (DEGs) were detected between HD and LD, of which 1935, 2390 and 1108 DEGs were found in the three comparisons(middle-upper, lower-outer and lower-inner), respectively. 274 common differentially expressed genes (co-DEGs) were contained in all three comparisons. Functional enrichment and KEGG pathway analysis found these genes were involved in Carbon fixation in photosynthetic organisms, Circadian rhythm, Photosynthesis - antenna proteins, Photosynthesis, chlorophyll metabolism, Porphyrin, sugar metabolism and so on. Among these genes, LHCB family participated in photosynthesis as parts of photosystem II. In addition, SPA1, rbcL, SNRK2, MYC2, BSK, SAUR and PP2C are involved in Circadian rhythm, the expression of genes related to glycometabolism and hormone signaling pathway is also changed. The results revealed that the decrease of plant density changed the photosynthetic efficiency of leaves and the expression of photosynthesis-related genes, which provide a theoretical basis for the actual production regulation of apples.

[Effects of thinning and reshaping on canopy micro-domain environment and leaf physiological characteristics in dense Fuji apple orchard on Loess Plateau of eastern Gansu, China]. / é—´ä¼æ”¹å½¢å¯¹é™‡ä¸œé«˜åŽŸå¯†é—­å¯Œå£«è‹¹æžœå›­å† å±‚å¾®åŸŸçŽ¯å¢ƒåŠå¶ç‰‡ç”Ÿç†ç‰¹æ€§çš„å½±å“.

We examined the effects of thinning and reshaping on the canopy micro-domain environment, leaves micro-structure, physiological characteristics and photosynthetic capacity of 16 year-old Fuji apple dense orchards by measuring canopy relative light intensity, temperature, relative humidity, leaf chlorophyll content, micro-structure, and photosynthetic fluorescence. After thinning and reshaping, relative light intensity and temperature of tree canopy were significantly improved, and the distribution was balanced. Effective light intensity (>30%) was 57% higher than that of control (thinning and reshaping, CK), and temperature increased by 1.1 ℃. Due to the improvement of relative light intensity and temperature in the canopy, leaf chlorophyll, leaf thickness, and palisade tissue thickness of thinning trees were increased by 8.7%, 5.4%, and 9.2%, respectively. Net photosynthetic rate, transpiration rate and stomatal conductance of the leaves were also significantly increased, being 12.6%, 17.1% and 7.3% higher than CK, respectively. Leaf photosynthesis capacity of both treatments was limited by non-stomatal factors. After thinning and reshaping, Fm (maximum fluorescence) and qN(non-photochemical quenching coefficient) of PSⅡ in leaves were increased by 1.5% and 2.1%. Leaves did not suffer strong light photoinhibition, with ABS/RC (unit reaction center absorbs light energy), ETo/RC (energy used for electron transfer captured by unit reaction center) and TRo/RC (energy captured by the unit reaction center to reduce QA) of leaves being significantly improved. The physiological characteristics of leaves were closely related to light and temperature environment. After thinning, light and temperature of the orchard canopy were improved, which promoted leaves growth and development, improved foliar micro-structure and photosynthetic efficiency. Thinning and reshaping were suitable strategies for the adjustment and optimization of Fuji orchard density in Loess Plateau of eastern Gansu.