The cultivation period of cassava in Kagoshima, Japan, which belongs to the temperate zone, is limited by the low temperature in winter. To maximize productivity under this limited period, investigations were conducted on the gas exchange rate and production structure relating to light utilization in a plant community of cassava grown under different nitrogen fertilization conditions. Fertilization either at planting or three months after planting significantly increased stomatal conductance in the upper canopy and root dry weight compared to the control. In addition, the dry matter distribution to stem and root dry matter rate of initial fertilization treatment were significantly higher, and the dry matter distribution to root of the latter fertilization treatment tended to be higher than that of the control. However, light transmittance at 80 cm below the top of the canopy was almost the same as that at the ground surface, which was a common tendency among the treatments. In conclusion, it was revealed that the effects of fertilization on yield were mainly the increase in the gas exchange rate of individual leaves and the change of dry matter distribution rather than an improvement in light transmittance.

Agriculture depends on the ability of seeds to survive until the next planting season under ambient conditions that may be averse to seed quality even when the seed is in a quiescent state. Seed priming invigorates seeds, but the impact on the longevity of seeds has limited its adoption. This study investigated the effect of the storage of primed rice seed on seed viability, vigor, and longevity. Three seed priming methods were employed on the rice cultivar New Rice for Africa (NERICA 4) seeds. Subsequently, the seeds were stored for 120 days at 25 °C and 65% relative humidity, simulating the ambient seed storage conditions of the tropics and sub-tropics. The primed seed recorded increased vigor compared to the non-primed seed until 90 days of storage. However, seed storage for 120 days reduced seed vigor and viability for all the seeds. The results indicated a significant reduction in seed vigor, increased solute leakage, generation of hydrogen peroxide, and accumulation of malondialdehyde after storage. Priming enhances cell membrane integrity and maintains seed vigor in storage at near ambient conditions long enough before reversal of its performance by the storage conditions. This assures that primed seed can either be stored until the following planting season or remain viable in the soil during delayed germination.

The effects of the application of bean sprout residue to soil on the soybean cyst nematode (SCN) Heterodera glycines were evaluated in pot experiments. When bean sprout residue was applied into a soil infested with SCN at a rate of 1%, the number of SCN second-stage juveniles (J2), measured with the Baermann method, increased after 14 days of application and then decreased markedly after 35 days, indicating that some J2 hatched in response to a stimulant in the bean sprout residue and then starved to death in the absence of a host. Next, bean sprout residue was applied two or four times and the number of SCN after 7 weeks was estimated with real-time PCR, which enables quantification of all the forms of SCN (eggs, J2, cysts). Results showed that the SCN density did not change in the untreated control, while it decreased by more than 70% in the residue treatment. Such a hatching-stimulatory and subsequent eradication effect was observed in the water extract of bean sprout residue. Among different parts of bean sprout, both of the stem and root parts had a higher stimulatory effect for hatching, while a stimulatory effect decreased in the stem part greened by culturing under light conditions. These results revealed that bean sprout residue might function as an environmental-friendly control measure for SCN.

While internal aeration in plants is critical for adaptation to waterlogging, there is a gap in understanding the differences in oxygen diffusion gradients from shoots to roots between hypoxia-tolerant and -sensitive species. This study aims to elucidate the differences in tissue oxygen concentration at various locations on the shoot and root between a hypoxia-tolerant species and a -sensitive species using a microneedle sensor that allows for spatial oxygen profiling. Job’s tears, a hypoxia-tolerant species, and sorghum, a hypoxia-susceptible species, were tested. Plants aged 10 days were acclimated to a hypoxic agar solution for 12 days. Oxygen was profiled near the root tip, root base, root shoot junction, stem, and leaf. An anatomical analysis was also performed on the roots used for the O₂ profile. The oxygen partial pressure (pO₂) values at the root base and tip of sorghum were significantly lower than that of the root of Job’s tears. At the base of the root of Job’s tears, pO₂ rapidly decreased from the root cortex to the surface, indicating a function to inhibit oxygen leakage. No significant differences in pO₂ between the species were identified in the shoot part. The root cortex to stele ratio was significantly higher from the root tip to the base in Job’s tears compared to sorghum. The pO₂ gradient began to differ greatly at the root shoot junction and root base longitudinally, and between the cortex and stele radially, between Job’s tears and sorghum. Differences in the root oxygen retention capacity and the cortex to stele ratio are considered to be related to differences in pO₂.