Transcriptomic and proteomic analyses of far-red light effects in inducing shoot elongation in the presence or absence of paclobutrazol in Chinese pine

In angiosperms, low red (R)/far-red (FR) ratio light increases gibberellin (GA) levels. GA signaling in conifer seedlings requires FR to promote shoot elongation and reduce the inhibition of shoot elongation induced by paclobutrazol (PAC), yet the effects of far-red light in inducing shoot elongation in the presence or absence of PAC is poorly understood. In this study, transcriptomic and proteomic analyses was used to examine the molecular mechanism of FR regulation of shoot elongation in Chinese pine (Pinus tabuliformis Carr.) seedlings in the presence of PAC. Four treatments were compared: white light + water (WW), FR + water (RW), white light + PAC (WP), and FR + PAC (RP), and 1436 differentially expressed genes (DEGs) and 450 differentially expressed proteins (DEPs) were identified in RW_WW (RW contrast WW), and 1862 DEGs and 481 DEPs in RP_WP (RP contrast WP). Metabolic and signal transduction pathway analyses of DEGs and DEPs in RW_WW and RP_WP, indicated that the former required more energy than the latter. Moreover, gibberellic acid, auxin, and brassinolide are equally important in RW_WW and RP_WP for shoot elongation, except for the ethylene pathway. Amino acid metabolism and cell wall organization were significantly enriched in RW_WW and RP_WP, respectively. In summary, RW_WW and RP_WP had different effects in secondary metabolism, energy metabolism, amino acid metabolism, cell wall organization, and hormone response. These results provide an important theoretical and reference basis for studying the regulatory effect of low R/FR and PAC in conifer shoot elongation.

Short-day treatment during the growing period limits shoot growth and increases frost hardiness of hybrid aspen plants in the nursery

In Finland, under nursery conditions hybrid aspen may continue their shoot growth until early September. Thus, frost hardening is usually delayed. To solve this problem, we used a three-week period of short-day （SD） treatment between late July and mid-August. During autumn after frost exposure, frost hardiness （FH） was assessed three times with a stem-browning test. The resuits showed that after SD treatment shoot growth ceased and FH increased when compared to untreated hybrid aspen. Furthermore, the height of SD-treated hybrid aspen varied much less than that of the control plants. We conclude that SD treatment in the nursery during the growing period can be used as a supplementary method for producing well-hardened and uniform hybrid aspen plants.

Soil Temperature Dependent Growth of Cotton Seedlings Before Emergence

Soil temperature is an important variable governing plant growth and development. Studies were conducted under laboratory conditions to determine the effect of soil temperature on root and shoot growth of cotton during emergence. Cotton seedlings were grown for 192 h at 20, 32 and 38℃ in soil packed in 300 mm long and 50 mm diameter cylinders. The data indicated that the longest roots （173 ram） as well as shoots （152 mm） were recorded at 32℃ followed by 20 （130 mm root and 82 mm shoot） and 38℃ （86 mm root and 50 mm shoot）. Roots grown at 20 and 38 ℃ were 20% and 50% shorter, respectively, than those grown at 32℃ after 192 h. Roots and shoots exhibited the lowest length and dry biomass at 38 ℃. Shoot lengths grown at 20 （74 mm） and 38℃（51 mm） were 44% and 61% shorter than those grown at 32℃（131 mm） after 180 h growth period, respectively. Growth at all three temperatures followed a similar pattern. Initially there was a linear growth phase followed by the reduction or cessation of growth. Time to cessation of growth varied with temperature and decreased faster at higher temperatures. Sowing of cotton should be accomplished before seedbed reaches a soil temperature （≥ 38 ℃） detrimental for emergence. Further, the seedbeds should be capable of providing sufficient moisture and essential nutrients for emerging seedling before its seed reserves are exhausted to enhance seedling establishment in soil.