Extreme temperatures are considered one of the main constraints that limit the growth and development of rice. We elucidated the root and shoot developmental plasticity of 64 rice genotypes during early seedling establishment, using the sunlit plant growth chambers at 22/14 (low), 30/22 (optimum), and 38/30 °C (high) day/night temperatures. Low temperature severely inhibited 23 traits, such as shoot (68%), root (57%), and physiological (35%) attributes. On the contrary, the high temperature positively affected most of the shoot (48%) and root (31%) traits, except root diameter and root/shoot ratio, compared with the optimum. Alternatively, leaf chlorophyll fluorescence-associated parameters declined under low (34%) and high (8%) temperatures. A weak correlation between cumulative high-temperature response index (CHTRI) and cumulative low-temperature response index (CLTRI) indicates the operation of different low- and high-temperature tolerance mechanisms at the early seedling stage. Groups of distinct rice genotypes associated with low or high-temperature tolerance were selected based on CHTRI and CLTRI. The genotypes that commonly performed well under low and high temperatures (IR65600-81-5-2-3, CT18593-1-7-2-2-5, RU1504114, RU1504122, Bowman, and INIA Tacuari) will be valuable genetic resources for breeders in developing early-season high- and low-temperature-tolerant genotypes for a broad range of both tropical and temperate rice-growing environments.

Drought is a major abiotic stress factor affecting the growth and development of plants at all stages. Developing a screening tool for identifying drought stress tolerance during seedling establishment is important in the deployment of rice varieties suited to water-limited growing environments. An experiment was conducted to evaluate 100 rice genotypes, mostly belonging to the tropical japonica subspecies, for drought stress tolerance using low-cost, pre-fabricated mini-hoop structures. The rice seedlings were subjected to two different soil moisture regimes- control pots managed at 100% and drought pots at 50% field capacity, from 12 to 30 days after sowing (DAS). Several morpho-physiological parameters including root traits were measured to assess the response of genotypes to drought stress. Significant moisture stress × genotype interactions were found for most of the parameters measured. A cumulative drought stress response index (CDSRI) was developed by adding the individual response indices of all cultivars. Based on CDSRI and standard deviation values, 5 and 28 genotypes were identified as highly sensitive and sensitive to drought, respectively, and 45 as moderately sensitive. On the other hand, 16 and 6 genotypes were classified as tolerant and highly tolerant to drought, respectively. Cheniere, a released cultivar, and RU1402174, an experimental breeding line, were identified as the least and most tolerant to drought among the 100 genotypes tested. Significant linear correlation coefficients were obtained between CDSRI and root growth parameters (R2 = 0.91, n = 100) and CDSRI with shoot growth parameters (R2 = 0.48, n = 100), revealing the importance of root traits in studying and identifying drought tolerant lines during the seedling establishment stages in rice. The tolerant rice genotypes identified will be valuable for rice scientists in studying the mechanism for early season drought as well as for rice breeders for developing new genotypes best suited under growing environments prone to early-season drought.

Ground-level UV-B will stay at a high level in the next several decades and influence sweet potato growth and yield because of the remaining chlorofluorocarbons in the atmosphere. The study explored three UV-B (none, ambient, and elevated/projected) levels on three contrasting sweet potato cultivars (Beauregard, Hatteras, and Louisiana 1188) using sunlit plant growth chambers at Mississippi State University. The results showed that UV-B influenced three cultivars differently. Growth, photosynthetic rate, epidermal and leaf structure of Beauregard were negatively influenced under ambient and elevated UV-B. On the contrary, Hatteras was positively influenced, and Louisiana 1188 was influenced by elevated UV-B positively on leaf thickness and waxes content, but negatively on the vine length, dry mass, and leaf area. In summary, Beauregard, Louisiana 1188, and Hatteras were UV-B sensitive, moderately sensitive, and tolerant, respectively. Developing UV-B tolerant cultivars will benefit under both current and projected UV-B exposures.

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Plants are excellent sources of secondary metabolites that have been used for the treatment of human diseases. The plant Momordica cymbalaria contains different types of phytochemicals like phenols, steroids, flavonoids, alkaloids and tannins. The present investigation was carried out to determine the bioactive compounds present in the different plant parts of Momordica cymbalaria by Gas chromatography-Mass spectroscopy (GC-MS) technique. Chromatograms and bioactive compounds of in vivo leaf, root and in vitro leaf callus methanolic extracts of Momordica cymbalaria are derived by GC-MS technique. 37 compounds were found in leaf methanolic extracts, 20 compounds in vitro leaf callus methanolic extracts and 18 compounds in root methanolic extracts. These are important bioactive compounds n-Hexadecanoic acid, 9-octadecenoic acid methyl ester,