Photosynthetic light curve, chlorophyll (Chl) content, Chl fluorescence parameters, malondialdehyde (MDA) content, phosphoenolpyruvate carboxylase (PEPC) activity and reactive oxygen metabolism were studied under drought stress in two autotetraploid rice lines and corresponding diploid rice lines. Net photosynthetic rate decreased dramatically, especially under severe drought stress and under high photosynthetic active radiation in diploid rice, while it declined less under the same conditions in autotetraploid lines. Compared with the corresponding diploid lines, the Chl content, maximum photochemical efficiency of photosystem (PS) II, and actual photochemical efficiency of PSII were reduced less in autotetraploid lines. PEPC activities were higher in autotetraploid rice lines. PEPC could alleviate inhibition of photosynthesis caused by drought stress. The chromosome-doubling enhanced rice photoinhibition tolerance under drought stress. The lower MDA content and superoxide anion production rate was found in the autotetraploid rice indicating low peroxidation level of cell membranes. At the same time, the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities were higher in autotetraploid rice lines. SOD, POD, and CAT could effectively diminish the reactive oxygen species and reduced the membrane lipid peroxidation.

The seeds of winter wheat were pretreated with three different doses of low-energy N(+) beams, and its seedlings were subjected to UV-B irradiation (10.08 kJ m(-2) day(-1)) at three-leaves stage. The growth characteristic of seeds, the oxidative damage to membrane system induced by UV-B radiation, and the alleviating effects of N(+) beams pretreatment to radiation damage were investigated. The results showed that the germination rate and seedling rate, respectively, increased 14.09 ± 1.03 and 13.91 ± 1.21 % compared with control (CK) at the dose of 4.0 × 10(16) ions/cm(2). When seedlings were exposed to UV-B radiation, the pretreatment method under the dose of 4.0 × 10(16) ions/cm(2) made the activity of peroxidase and superoxide dismutase increasing, the content of chlorophyll enhancing, but the content of malondialdehyde reducing significantly compared with that of the single UV-B radiation. Whereas, the activity of catalase irradiated by UV-B improved notably under the pretreatment dose of 8.0 × 10(16) ions/cm(2). In addition, after being irradiated with UV-B, the content of soluble protein and glutathione whose seeds were pretreated by the dose of 6.0 × 10(16) ions/cm(2) were higher than that of the single UV-B radiation. It was suggested that the suitable dose of low-energy ion beams pretreatment to wheat seeds could change its physiological characteristics at seedlings stage to alleviate the damage effects from UV-B radiation.

Net photosynthetic rate (PN), photorespiration (PR), chlorophyll (Chl) content, Chl fluorescence parameters, starch accumulation, and related key enzyme activities were determined during the grain-filling stage in two autotetraploid lines and corresponding diploid rice lines. The results showed that autotetraploid rice lines had a higher Chl content, PN, electron transport rate, maximum photochemical efficiency of PSII, actual photochemical efficiency of PSII, and lower PR in leaves than that in corresponding diploid rice lines during the grain-filling stage. It indicated that autotetraploid rice line had a high photosynthetic capacity and high light-utilization efficiency. The activities of ADP-glucose pyrophosphorylase, soluble starch synthase, and starch-branching enzyme in grains of autotetraploid rice lines were higher than those in grains of corresponding diploid rice lines during the grain-filling stage. Therefore, autotetraploid rice lines were more efficient than corresponding diploid rice lines in converting photosynthetic products into starch.

The objective of the study is to investigate the biological effects of N(+) beam implantation in different ploidy rice. N(+) beam implantation had increase effect in tillers number, spikelet fertility, grain yield per plant, si-phellem cell size, photosynthetic rate, transpiration rate, flag leaf dry weight, flag leaf culm dry weight, stomatal length, vascular bundle area, and protein and starch content and decrease effect in 1,000-grain weight, stomatal width and chlorophyll, calcium, sodium, and zinc content for all rice lines. N(+) beam implantation had opposite effect on diploid and autotetraploid rice lines in vascular bundle area, stomatal complexes areas, epidermal cell size, era length, area of air spaces, midrib length, papilla number, flag leaf length, flag leaf width, flag leaf area, and cadmium, copper, ferrum, magnesium and phosphorus content. Twenty traits of diploid line and ten traits of autotetraploid line are significantly increased by N(+) beam in this experiment, ranging from 6.8 to 362.7 % in diploid line and 7.9 to 131.7 % in autotetraploid line. Six traits of diploid lines and 15 traits of autotetraploid line are significantly decreased by N(+) beam implantation in this experiment, ranging from 8.9 to 87.4 % in diploid line and 5.6 to 88.5 % in autotetraploid line.