Increasing leaf transpiration efficiency (TE) may provide leads for growing rice like dryland cereals such as wheat (Triticum aestivum). To explore avenues for improving TE in rice, variations in stomatal conductance (gs) and mesophyll conductance (gm) and their anatomical determinants were evaluated in two cultivars from each of lowland, aerobic, and upland groups of Oryza sativa, one cultivar of O. glaberrima, and two cultivars of T. aestivum, under three water regimes. The TE of upland rice, O. glaberrima, and wheat was more responsive to the gm/gs ratio than that of lowland and aerobic rice. Overall, the explanatory power of the particular anatomical trait varied among species. Low stomatal density mostly explained the low gs in drought-tolerant rice, whereas rice genotypes with smaller stomata generally responded more strongly to drought. Compared with rice, wheat had a higher gm, which was associated with thicker mesophyll tissue, mesophyll and chloroplasts more exposed to intercellular spaces, and thinner cell walls. Upland rice, O. glaberrima, and wheat cultivars minimized the decrease in gm under drought by maintaining high ratios of chloroplasts to exposed mesophyll cell walls. Rice TE could be improved by increasing the gm/gs ratio via modifying anatomical traits.

Aims: To face the challenge of decreasing freshwater availability for agriculture, it is important to explore avenues for developing rice genotypes that can be grown like dryland cereals. Roots play a key role in plant adaptation to dry environments. Methods: We examined anatomical and histochemical root traits that affect water acquisition in rice (Oryza sativa) and wheat (Triticum aestivum). These traits and root growth were measured at two developmental stages for three rice and two wheat cultivars that were grown in pots under three water regimes. Results: Wheat roots had larger xylem sizes than rice roots, which potentially led to a higher axial conductance, especially under water-deficit conditions. Suberization, lignification and thickening of the endodermis in rice roots increased with increasing water deficit, resulting in stronger radial barriers for water flow in rice than in wheat, especially near the root apex. In addition, water deficit strongly impeded root growth and lateral root proliferation in rice, but only slightly in wheat, and cultivars within a species differed little in these responses. The stress sensitivity of rice attributes was slightly more prominent at vegetative than at flowering stages. Conclusions: Rice root characteristics, which are essential for growth under inundated conditions, are not conducive to growth under water deficit. Although rice roots show considerable plasticity under different watering regimes, improving root xylem size and reducing the radial barriers would be required if rice is to grow like dryland cereals.

Increasing fresh water scarcity is a major constraint for rice (Oryza sativa) productivity under future climatic conditions. It is important to understand why rice cannot perform like other dryland cereals, when grown under drier soil conditions. The responses of plant growth, plant water status, leaf and stem anatomical attributes to soil water deficit were examined at two developmental stages of three rice and two wheat (Triticum aestivum) cultivars grown under three water regimes in a pot experiment. Yield and yield components were determined at plant maturity. The stress sensitivity of plant growth was slightly more prominent at vegetative than at flowering stages. Water deficit limited root growth but had little impact on above‐ground growth in rice plants. The xylem system of the leaves was more developed in rice than in wheat, but the opposite was true for the root xylem system. Compared with stem xylem attributes, leaf xylem attributes played a larger role in modulating leaf water potential under water deficit. In addition, the variation in yield response to water deficit between various types of rice, and between rice and wheat was closely associated with the response of leaf water potential to water deficit. To grow rice in drier conditions, its xylem system should be balanced by increasing root growth and modifying leaf anatomy.

NAC (NAM, ATAF1/2, and CUC2) transcription factors are unique and essential for plant growth and development. Although the NAC gene family has been identified in a wide variety of plants, its chromosomal location and function in Cannabis sativa are still unknown. In this study, a total of 69 putative CsNACs were obtained, and chromosomal location analysis indicated that the CsNAC genes mapped unevenly to 10 chromosomes. Phylogenetic analyses showed that the 69 CsNACs could be divided into six subfamilies. Additionally, the CsNAC genes in group IV-a are specific to Cannabis sativa and contain a relatively large number of exons. Promoter analysis revealed that most CsNAC promoters contained cis-elements related to plant hormones, the light response, and abiotic stress. Furthermore, transcriptome expression profiling revealed that 24 CsNAC genes in two Cannabis sativa cultivars (YM1 and YM7) were significantly differentially expressed under osmotic stress, and these 12 genes presented differential expression patterns across different cultivars according to quantitative real-time PCR (RT–qPCR) analysis. Among these, the genes homologous to the CsNAC18, CsNAC24, and CsNAC61 genes have been proven to be involved in the response to abiotic stress and might be candidate genes for further exploration to determine their functions. The present study provides a comprehensive insight into the sequence characteristics, structural properties, evolutionary relationships, and expression patterns of NAC family genes under osmotic stress in Cannabis sativa and provides a basis for further functional characterization of CsNAC genes under osmotic stress to improve agricultural traits in Cannabis sativa.

Summary: Theoretically, the PEP‐CK C₄ subtype has a higher quantum yield of CO₂ assimilation () than NADP‐ME or NAD‐ME subtypes because ATP required for operating the CO₂‐concentrating mechanism is believed to mostly come from the mitochondrial electron transport chain (mETC). However, reported is not higher in PEP‐CK than in the other subtypes. We hypothesise, more photorespiration, associated with higher leakiness and O₂ evolution in bundle‐sheath (BS) cells, cancels out energetic advantages in PEP‐CK species. Nine species (two to four species per subtype) were evaluated by gas exchange, chlorophyll fluorescence, and two‐photon microscopy to estimate the BS conductance (g_bs) and leakiness using a biochemical model. Average g_bs estimates were 2.9, 4.8, and 5.0 mmol m⁻² s⁻¹ bar⁻¹, and leakiness values were 0.129, 0.179, and 0.180, in NADP‐ME, NAD‐ME, and PEP‐CK species, respectively. The BS CO₂ level was somewhat higher, O₂ level was marginally lower, and thus, photorespiratory loss was slightly lower, in NADP‐ME than in NAD‐ME and PEP‐CK species. Differences in these parameters existed among species within a subtype, and g_bs was co‐determined by biochemical decarboxylating sites and anatomical characteristics. Our hypothesis and results partially explain variations in observed , but suggest that PEP‐CK species probably use less ATP from mETC than classically defined PEP‐CK mechanisms.