Stomata variation in the process of polyploidization in Chinese chive (Allium tuberosum).

BACKGROUND: Stomatal variation, including guard cell (GC) density, size and chloroplast number, is often used to differentiate polyploids from diploids. However, few works have focused on stomatal variation with respect to polyploidization, especially for consecutively different ploidy levels within a plant species. For example, Allium tuberosum, which is mainly a tetraploid (2n = 4x = 32), is also found at other ploidy levels which have not been widely studied yet. RESULTS: We recently found cultivars with different ploidy levels, including those that are diploid (2n = 2x = 16), triploid (2n = 3x = 24), pseudopentaploid (2n = 34-42, mostly 40) and pseudohexaploid (2n = 44-50, mostly 48). GCs were evaluated for their density, size (length and width) and chloroplast number. There was no correspondence between ploidy level and stomatal density, in which anisopolyploids (approximately 57 and 53 stomata/mm2 in triploid and pseudopentaploid, respectively) had a higher stomatal density than isopolyploids (approximately 36, 43, and 44 stomata/mm2 in diploid, tetraploid and pseudohexaploid, respectively). There was a positive relationship between ploidy level and GC chloroplast number (approximately 44, 45, 51, 72 and 90 in diploid to pseudohexaploid, respectively). GC length and width also increased with ploidy level. However, the length increased approximately 1.22 times faster than the width during polyploidization. CONCLUSIONS: This study shows that GC size increased with increasing DNA content, but the rate of increase differed between length and width. In the process of polyploidization, plants evolved longer and narrower stomata with more chloroplasts in the GCs.

[Effects of exogenous Ca2+ on D1 protein phosphorylation and PS II performances of wheat leaf chloroplasts under high temperature and illumination stress].

Aimed to understand the effects of exogenous Ca2+ on the D1 protein phosphorylation and PS II performances of wheat leaf chloroplasts under high temperature and illumination stress, wheat leaves at grain-filling stage were sprayed with 10 mmol x L(-1) of CaCl2 or water (as control), and then subjected to high temperature and illumination stress (35 degrees C and 1600 micromol x m(-2) x S(-1)) for various hours, with the changes in photosynthetic electron transport rate (ETR), net photosynthetic rate, chlorophyll fluorescence parameters, and relative amount of phosphorylated and nonphosphorylated D1 protein in thylakoid membranes determined. After spraying with Ca2+, the PS II reaction center under the stress was reversibly inactivated, the net degradation of D1 protein was effectively restrained, the D1 protein phosphorylation was maintained at a higher level, and the ETR of whole chain and PS II, the maximal photochemical efficiency of PS II (F(v)/F(m)), the actual photochemical efficiency of PS II (phi(PS II), the photochemical quenching coefficient (qp), and net photosynthetic rate (P(n)) were all higher, suggesting that exogenous Ca2+ could improve the PS II performances and mitigate its damage under high temperature and illumination stress via regulating the turnover of D1 protein in wheat leaf chloroplasts.

[Effects of salicylic acid on D1 protein phosphorylation and PS II performance in wheat leaf chloroplasts under high temperature and high light stress].

To study the effects of salicylic acid (SA) on the D1 protein phosphorylation and PS II performance in wheat (Tritivum aestivum L.) leaf chloroplasts under high temperature and high light, the wheat leaves at grain-filling stage were sprayed with SA solution (0.5 mmol x L(-1)) or water (as control), and then subjected to 35 degrees C and 1600 micromol x m(-2) x s(-1) for various hours. The changes in electron transport rate (ETR), net photosynthetic rate, chlorophyll fluorescence parameters, and relative amount of phosphorylated and nonphosphorylated D1 protein in thylakoid membrane were compared. The results showed that foliar spraying SA effectively inhibited the degradation of D1 protein under high temperature and high light stress, and maintained the D1 protein phosphorylation, ETR of whole chain and PS II, Fv/Fm (the maximal photochemical efficiency of PS II), phi(PS II) (the actual photochemical efficiency of PS II), q(p)(the photochemical quenching coefficient), and Pn (net photosynthetic rate) at a higher level, indicating that exogenous SA could mitigate the damage effect of high temperature and high light on wheat leaf photosynthetic apparatus and benefit PS II performance via regulating the turnover of D1 protein in chloroplasts.