Crop Load Affects Vegetative Growth Flushes and Shoot Age Influences Irreversible Commitment to Flowering of `Hass' Avocado

Abstract

<jats:p>Several studies were undertaken in commercial nonirrigated `Hass' avocado orchards under the subhumid semiwarm subtropical climate of the state of Nayarit, Mexico, with the following objectives: 1) to determine the frequency and intensity of vegetative shoot flushes and their contribution to the production of floral shoots, 2) to quantify the effect of tree fruit load on the occurrence of vegetative shoot flushes during the year and the relationship between vegetative and reproductive shoot number during flowering, and 3) to determine the time when apical buds borne on the major vegetative shoot flushes reached irreversible commitment to flowering (floral determination) through the use of shoot defoliation and girdling. Data trees were selected in two orchards based on their current crop load. Four to five branches per tree were tagged, and the number and intensity of vegetative flushes that developed during 2 years, as well as the type of growth produced by apical buds of shoots of different ages, were recorded at the end of the winter bloom periods for two separate years, 1999 and 2001. In a separate experiment using a different set of trees, winter and summer flush shoots were defoliated (year 1) or defoliated and girdled (year 2) at different stages of bud development from September to January in each case. Four vegetative flushes occurred each year. The winter flush that emerged in Feb. 1998 made the greatest contribution to the 1999 winter bloom—76.5% of the shoots produced floral shoots. Contributions of the summer 1 (late July 1998), summer 2 (early Aug. 1998), and summer 3 (late Aug. 1998) flushes to flowering were intermediate. A total of 30.6%, 36.4%, and 19% of the shoots produced floral shoots respectively. All four vegetative flushes produced a similar number of vegetative shoots during winter bloom. Evaluation of the 2001 winter bloom for trees with high (&gt;95 kg fruit/tree) and low (&lt;70 kg fruit/tree) crops showed no effect of tree fruit load on the production of vegetative or floral shoots by winter or summer vegetative flushes. Irrespective of time of treatment (shoot defoliation and girdling) or shoot age, irreversible commitment to flowering of apical buds occurred by 15 Oct., and this stage was associated with an average of 27.5 chilling days (temperature, ≤19 °C) for both years. Buds irreversibly committed to flowering were closed and pointed, with partial senescence of bud scales. Anatomically, the buds showed a convex primary axis meristem and four secondary axis floral shoot meristems.</jats:p>

Response of peach tree leaf area to seasonal variation in tropical climate

“…Peach trees cultivated in these regions may present difficulties for promoting and suspension growth, what will account for problems regarding the normal flow of the so-called circadian cycle of plants throughout the year. Under vegetative growing conditions in tropical regions, tree growth may occur in the form of "vegetative growth flushes", which may vary in number of occurrence, intensity and duration, according to the time of year, or to environmental/hormonal stimulus received by plants like what occurs in other plant species such as mangoes and avocado trees (Yeshitela et al, 2004;Salazar-García et al, 2006). The occurrence of these "flushes" may alter the establishment of the total leaf area and also of the individual leaf area of the leaves.…”

Cinética De Crecimiento Foliar Y Desarrollo De Brotes en Selecciones Injertadas De Zapote Mamey

“…The months where the buds grew best were from June to September for the three materials; this coincides with the rainy season and with increasing temperature. y dependiendo de las condiciones climáticas, así como de la carga de fruto en el árbol, se pueden presentar de dos a cuatro flujos al año (Salazar-García et al, 2006).…”

“…In mango, Avilan et al (2000) observed that, the bud growth is rhythmic with three or four vegetative flows from 30 to 40 days of duration each year, but this feature can be modified by pruning, since pruned-trees develop up to four growth streams in nine months, while non-pruned trees had one or two streams. In avocado, growth also occurs as vegetative flows depending on weather conditions and the load of fruit on the tree, there may be two or four flows per year (Salazar- García et al, 2006).…”

Robinia pseudoacacia L. in Short Rotation Coppice: Seed and Stump Shoot Reproduction as well as UAS-based Spreading Analysis

“…The biomass production differs compared to non-harvested trees, especially for black locust [33]. To account for this, specific yield tables and growth models for coppices of different broad-leafing tree species were developed [34][35][36][37][38][39][40][41][42][43][44][45][46]. Moreover, in nutrient-poor and sandy forest stands, a decreasing number of black locust stump shoots with increasing shoot age and a wide variety of stump shoots depending on the stump distance and stump age was observed [47,48].…”