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Ungrafted trees of seven apple rootstock cultivars, M.4, M.7, M.11, M.26, M.27, MM.106, and Maru. bakaidou (Malus prunifolia Borkh. var. ringo Asami; weeping type), and `Fuji' (Malus domestics Borkh.) trees grafted on these seven plus M.9 and M. 16 rootstock were grown in sand. They were regularly supplied with nutrient solutions of N as ammonium alone (A), nitrate alone (T), and both (AT). With both ungrafted and grafted trees, the shoot growth of six rootstock (M.11, M.4, M.7, MM.106, M.26, and M.27) was significantly less with A than with T. With `Fuji' trees grafted on the above six rootstock, the number of flowering buds and the ratios of flowering buds to total emerged buds were significantly enhanced by treatments A and AT, especially in the formation of axillary flowering buds. Flowering and shoot growth of `Fuji' trees grafted on M. prunifolia and M.16 were slightly affected by the form of supplied N. In the xylem sap, cytokinin-like activity was detected in a single zone in paper chromatography in all rootstock and `Fuji' trees. The activity in six ungrafted rootstock (M.4, M.7, M.11, M.26, M.27, and MM.106) and `Fuji' trees grafted on these plus M.9 rootstock were higher with A than with T. Gibberellin-like activity in the same sap was detected in two zones, Rfs 0.3 to 0.4 and Rfs 0.7 to 0.8 in paper chromatography. In the six ungrafted rootstock and in `Fuji' trees grafted on these plus M.9, A led to higher activity at Rfs 0.7 to 0.S, but T led to higher activity at Rfs 0.3 to 0.4. Cytokinin-like and gibberellin-like activities in ungrafted M. prunfolia and `Fuji' trees grafted on M. prunifolia or M.16 were not affected by the form of N.
The seeds of difficult-to-germinate native species of American licorice (Glycyrrhiza lepidota Pursh), angelica (Angelica atropurpurea L.), wild blueberry (Vaccinium angustifolium Ait.), wild mint (Mentha arvensis L.), and purple coneflower (Echinacea angustifolia D.C.), were soaked in 0, 2.5, 5.3, or 7.6 m KOH solutions for 0, 1, 5, 10, 15, or 20 minutes. After these treatments, germination was determined at 10 °C with a 14-hour photoperiod in petri dishes and seedling emergence was conducted at 14/10 °C with a 14-hour photoperiod in a sandy loam soil. In general, KOH treatment for only 1 min enhanced germination and seedling emergence. The optimal KOH concentration and soaking time in improving seed germination and seedling emergence varied with species, being 5.3 m and 10 min for purple coneflower, 5.3 m and 5 minutes for wild blueberry, 7.6 m and 5 minutes for angelica, 7.6 m and 1 minute for wild mint, and 5.3-7.6 m and 10 minutes for American licorice, respectively. Prolonged soaking, particularly in high concentrations, reduced germination and emergence.
Hydrogen sulfide (H2S) was recently recognized as an endogenous gaseous molecule involved in seed germination, root organogenesis, abiotic stress tolerance, guard cell movement, and delay of senescence in plants. In the present study, we show that H2S participates in the regulation of postharvest ripening and senescence in fresh-cut kiwifruit, Actinidia deliciosa. Fumigation of fresh-cut kiwifruit with the H2S donor sodium hydrosulfide (NaHS) solution prolonged kiwifruit storage time and alleviated senescence and tissue softening in a dose-dependent manner at an optimal concentration of 1.0 mmol·L−1 NaHS. H2S treatment maintained higher levels of reducing sugars, soluble proteins, free amino acids, ascorbate, and chlorophyll and lowered carotenoid levels. H2S treatment also significantly decreased the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion (•O2 −) during fruit storage compared with water controls. Furthermore, the activities of guaiacol peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were increased by H2S treatment, whereas the activity of lipoxygenase (LOX) was decreased compared with untreated controls. Taken together, these results suggest that H2S is involved in prolonging postharvest shelf life and plays an antioxidative role in fresh-cut kiwifruit.