Joe M. Bradford

Is Chilling a Prerequisite for Flowering and Fruiting in ‘Arbequina’ Olives?

Abstract It is generally thought that olives (Olea europaea) require several days (over 80 days) of chilling temperatures (7.2°C) for flower induction; minimum nighttime temperatures of 2-4°C and maximum daytime temperature of 15.5-19°C are considered optimum for flower and fruit production. Environmental chamber studies were conducted on potted olive trees for the purpose of defining flowering conditions for ‘Arbequina’. We repeatedly observed that good flower and fruit production in ‘Arbequina’ can be achieved even when the plants are not subjected to “chilling” temperatures or any chilling criteria that had previously been described necessary for flower and fruit production in olives. This phenomenon could be of great practical value because the results obtained can be exploited to cultivate olives in subtropical climates (e.g., southern and coastal Texas) where typical “chilling” temperatures are not commonly observed for prolonged periods of time.

Plant Growth Regulatory Effects of Chicken Litter Extract

ABSTRACT Chicken litter is often used in organic farming as a source of plant food, and to improve soil organic matter and microbial populations. Both positive and negative effects of such an amendment have been reported. Because of the complex interactions involving soil, plant, and microbial populations in the most common test systems, it is difficult to attribute the observed plant responses to any one component of the test system affected by chicken litter. We have therefore conducted studies on the chicken litter extracts in a soil-less system to ascertain whether chicken litter affects plants simply by providing plant nutrients or if it also affects plants through plant growth regulatory substances. Since chicken litter is generally rich in available ammonium nitrogen, we studied the effects of chicken litter extract on ammonium induced rise in putrescine levels in oat leaves. Our results showed increases in putrescine levels in oat leaves floating on ammonium sulfate solution (0.033%) but not in leaves floating on chicken litter extract containing equivalent amount of ammonium nitrogen. Mixing chicken litter extract with the ammonium sulfate inhibited the ammonium induced rise in putrescine levels thus supporting the hypothesis that regulatory substances in chicken litter extract affect plant growth. In addition, our experiments showed that chicken litter extracts inhibited root growth in cowpeas that could not be attributed to the levels of ammonium nitrogen present in the extract. In fact, emerging roots of young cowpea seedlings exhibited an anti-geotropic response more akin to hormonal effects than a nutritional phenomenon.