Foliar Thidiazuron Promotes the Growth of Axillary Buds in Strawberry

Strawberry (Fragaria × ananassa Duch.) can be easily propagated with daughter plants or through crown division, which are developed from the axillary bud at the axils of leaves. This study was conducted to investigate the effects of different cytokinins, auxins, and their combinations on the axillary bud growth in strawberry. Four cytokinins (6-benzyladenine, kinetin, zeatin, and thidiazuron (TDZ)) and three auxins (indole-3-acetic acid, indole-3-butyric acid, and naphthaleneacetic acid) at a concentration of 50 mg·L−1 were sprayed on the leaves three times in 10-day intervals. The expression levels of cytokinin, auxin, and meristem-related genes in the crowns were also investigated. The results showed that TDZ was the most effective hormone for the axillary bud growth, and also promoted plant growth. However, chlorophyll, soluble sugar, and starch contents in the leaves were lower after TDZ. TDZ activated the cytokinin signal transduction pathway, while repressing the auxin synthesis genes. Several meristem-related transcription factors were upregulated, which might be essential for the growth of the axillary buds. These results suggested that TDZ can improve the cultivation of strawberry, while further research is needed to explain the effect on phytochemistry.

Responses of leaf morphology, NSCs contents and C:N:P stoichiometry of Cunninghamia lanceolata and Schima superba to shading

Background: The non-structural carbohydrates (NSCs), carbon (C), nitrogen (N), and phosphorus (P) are important energy source or nutrients for all plant growth and metabolism. To persist in shaded understory, saplings have to maintain the dynamic balance of carbon and nutrients, such as leaf NSCs, C, N and P. To improve understanding of the nutrient utilization strategies between shade-tolerant and shade-intolerant species, we therefore compared the leaf NSCs, C, N, P in respond to shade between seedlings of shade-tolerant Schima superba and shade-intolerant Cunninghamia lanceolate. Shading treatments were created with five levels (0%, 40%, 60%, 85%, 95% shading degree) to determine the effect of shade on leaf NSCs contents and C:N:P stoichiometry characteristics.Results: Mean leaf area was significantly larger under 60% shading degree for C. lanceolata while maximum mean leaf area was observed under 85% shading degree for S. superba seedlings, whereas leaf mass per area decreased consistently with increasing shading degree in both species. In general, both species showed decreasing NSC, soluble sugar and starch contents with increasing shading degree. However shade-tolerant S. superba seedlings exhibited higher NSC, soluble sugar and starch content than shade-intolerant C. lanceolate. The soluble sugar/starch ratio of C. lanceolate decreased with increasing shading degree, whereas that of S. superb remained stable. Leaf C:N ratio decreased while N:P ratio increased with increasing shading degree; leaf C:P ratio was highest in 60% shading degree for C. lanceolata and in 40% shading degree for S. superba. Conclusion: S. superba is better adapted to low light condition than C. lanceolata through enlarged leaf area and increased carbohydrate reserves that allow the plant to cope with low light stress. From mixed plantation viewpoint, it would be advisable to plant S. superba later once the canopy of C. lanceolata is well developed but allowing enough sunlight.

Using electrical impedance tomography for rapid determination of starch and soluble sugar contents in Rosa hybrida

Background Soluble sugar and starch, as carbon sources, directly participate in plant metabolism by providing energy. Conventional determination of plant starch and soluble sugar content usually involves destructive sampling, complicated procedures, and considerable amounts of chemicals and labor. Therefore, there is an urgent need to develop a non-destructive and rapid method for determining plant starch and soluble sugar contents. Electrical impedance tomography (EIT) technology has been used to determine the physiological state and cold resistance of plant tissues. However, so far there have been no reports on the use of EIT for the rapid estimation of soluble sugar and starch contents. Results In this study, EIT was used to obtain reconstructed voltage values and estimate starch and soluble sugar contents in the stems of three Rosa hybrida cultivars during February to May. Stems from two of the cultivars were used for establishing regression models for starch and soluble sugar contents as functions of reconstructed voltage values. The third cultivar was used to test the accuracy of the regression models. The results showed that the reconstructed voltage value significantly correlated with soluble sugar and starch contents. The quadratic regression model was best for determining soluble sugar content and the logarithmic regression model was best for determining starch content. Conclusions Thus, we preliminarily established and verified regression models for estimating soluble sugar and starch contents using reconstructed voltage values of rose stems. These data provide technical support for using EIT to analyze changes in physiological parameters and to rapidly estimate physiological indexes of plants.

RESPONSE OF SUB1 INTROGRESSION LINES OF RICE TO VARIOUS FLOODING CONDITIONS

Two types of floods can be happen in rice crops, i.e. flash floods and stagnant floods. Flash floods cause complete submergence for up to 2 weeks, while stagnant floods (SF) could partially submerge part of rice plant. To overcome yield loss due to the floods, introgression of SUB1 gene, known as a gene suppressing cell elongation and carbohydrate metabolism, to rice genotype can increase plant tolerance to complete submergence for 10 days or more. The study aimed to evaluate the response of 18 rice genotypes, including the recently developed sixth pair SUB1 near isogenic lines (NILs) of mega-rice varieties (Swarna, Sambha Mahsuri, IR64, TDK1, BR11, and CR1009), to various flooding conditions. The rice genotypes were planted at field ponds at Los Banos, Philippines, in the wet season (WS) of 2009. The treatments were 15 days submergence, SF, SF follows submergence and normal conditions. Each treatment was arranged in completely randomized block design with three<br />replications. The results showed that the SUB1 introgression rice lines had higher survival compared to the non-SUB1 and did not much elongate their shoots during submergence. Nevertheless, under SF the rice genotypes should elongates their shoots to allow restoring contact with the air. SF and SF follows submergence decreased the panicle number, grain<br />number per panicle and panicle fertility. Consequently, the yield declined. It suggests that sensitive genotypes are mostly sourcelimited during grain filling. The SUB1 introgression lines had higher chlorophyll concentration and less depletion in soluble sugar and starch after submergence. Under SF, soluble sugar and starch contents between the SUB1 NILs and non-SUB1 lines were not significantly different. Introgression of the SUB1 into high-yielding varieties improved submergence tolerance without affecting yield potential. The study indicates that introgression of the SUB1 into taller type rice varieties should be done to compensate the effect of suppressed elongation. <br />

RESPONSE OF SUB1 INTROGRESSION LINES OF RICE TO VARIOUS FLOODING CONDITIONS

Two types of floods can be happen in rice crops, i.e. flash floods and stagnant floods. Flash floods cause complete submergence for up to 2 weeks, while stagnant floods (SF) could partially submerge part of rice plant. To overcome yield loss due to the floods, introgression of SUB1 gene, known as a gene suppressing cell elongation and carbohydrate metabolism, to rice genotype can increase plant tolerance to complete submergence for 10 days or more. The study aimed to evaluate the response of 18 rice genotypes, including the recently developed sixth pair SUB1 near isogenic lines (NILs) of mega-rice varieties (Swarna, Sambha Mahsuri, IR64, TDK1, BR11, and CR1009), to various flooding conditions. The rice genotypes were planted at field ponds at Los Banos, Philippines, in the wet season (WS) of 2009. The treatments were 15 days submergence, SF, SF follows submergence and normal conditions. Each treatment was arranged in completely randomized block design with three<br />replications. The results showed that the SUB1 introgression rice lines had higher survival compared to the non-SUB1 and did not much elongate their shoots during submergence. Nevertheless, under SF the rice genotypes should elongates their shoots to allow restoring contact with the air. SF and SF follows submergence decreased the panicle number, grain<br />number per panicle and panicle fertility. Consequently, the yield declined. It suggests that sensitive genotypes are mostly sourcelimited during grain filling. The SUB1 introgression lines had higher chlorophyll concentration and less depletion in soluble sugar and starch after submergence. Under SF, soluble sugar and starch contents between the SUB1 NILs and non-SUB1 lines were not significantly different. Introgression of the SUB1 into high-yielding varieties improved submergence tolerance without affecting yield potential. The study indicates that introgression of the SUB1 into taller type rice varieties should be done to compensate the effect of suppressed elongation. <br />