Low temperature and drought stress are the major constraints in rice productivity worldwide. This study investigated the influence of low soil temperature and/or drought stress on physiology and pollen traits of two rice genotypes viz., Guinongzhan and Yueza 763 at flowering stage. The experiment included four treatments, i.e., under the greenhouse natural growth conditions (UC) taken as control, drought stress (DS), the soil water potential was kept at ?0.035 to ?0.045 MPa (DS), low soil temperature (LT) maintained at 19 to 21℃, combined LT and DS (LT+DS, LD). Results showed that LT, DS, and LD substantially reduced net photosynthetic rate (Pn) and the maximal photochemical efficiency of PSII (Fv/Fm), whilst transpiration rate (Tr) was markedly enhanced by under LT in both rice genotypes. The malondialdehyde (MDA) contents were enhanced under LT, DS, and LD in Guinongzhan, whilst the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were regulated by LT, DS, and LD in both rice genotypes. Furthermore, anther dehiscence rate, pollen numbers on stigma, pollen viability and pollen germination rate, and anther starch contents were obviously reduced under LT and DS of both rice genotypes. Stress conditions substantially reduced the yield and yield components, i.e., effective panicles, seed set percentage, grain/panicles, 1000-grain weight, and grain yield of both genotypes and the effects were more apparent in Guinongzhan than those in Yueza 763 whilst combined LT and DS proved more damaging than individual stress.
Climate conditions is an important factor affected the fragrant rice growth and development.In order to study the effects of different planting seasons on fragrant rice performance in South China,present study was conducted with three planting seasons(early season(April to July),middle season(June to September)and late season(August to November))and three fragrant rice cultivars,‘Basmati-385’,‘Meixiangzhan-2’and‘Xiangyaxiangzhan’.The results showed that the highest grain yield and grain 2-acetyl-1-pyrroline(2-AP,key component of fragrant rice aroma)content were both recorded in late season treatment while the fragrant rice in middle season treatment produced the lowest grain yield,grain filling percentage,1000-grain weight and gain 2-AP content.The highest contents of precursors(proline,pyrroline-5-carboxylic acid and 1-pyrro-line)which related to 2-AP biosynthesis were recorded in late season treatment compared with early season treatment and middle season treatment.The highest activities of enzymes(proline dehydrogenase,pyrroline-5-carboxylic acid synthetase and ornithine transaminase)which involved in 2-AP biosynthesis were also observed in late season treatment.Moreover,the fragrant rice cultivars in late season possessed the lowest chalk rice rate,chalkiness as well as the highest brown rice rate,head rice and protein content.Thus,the optimal season for fragrant rice production in South China is the late season.
