Effects of High Intensity Ultrasound Stimulation on the Germination Performance of Caper Seeds.

The caper bush has developed different mechanisms to survive in Mediterranean conditions, such as drought tolerance and seed dormancy. Many studies have been carried out to improve the germination of caper seeds, but ultrasound is one of the least studied methodologies in this species. This study aimed to analyze the effects of treatments with an ultrasonic probe processor on the imbibition and germination of caper seeds. After applying the ultrasound treatment using three output powers and three holding times, the seed coat's disruption level was determined, and the imbibition, viability and germination tests were carried out. Ultrasonication fastens the initial imbibition, but after 48 h of soaking, seed moisture does not present differences compared to non-sonicated seeds. It produces the scarification of the testa but does not affect the tegmen, so moistening occurs through the hilar region, as in control seeds. There is a significant linear and negative correlation between the germination of the seeds and the temperature reached during the sonication treatment, so that temperatures above 40 °C practically annulled the germination. The combination of 20 W and 60 s provided the greatest germination percentage, being the only treatment that statistically improves germination in relation to the control seeds. When the output power and/or holding time were higher, the temperature increased, and the germination percentage statistically decreased.

Influence of Seed-Covering Layers on Caper Seed Germination.

Caper is a perennial shrub that is widespread in the Mediterranean Basin. Although the fruits contain many seeds, they germinate slowly and with very low percentages, due to their nondeep physiological dormancy. The influence of the testa and endosperm, as well as the effect of applying gibberellic acid (GA3) solutions on seed germination to release its dormancy, are reported in this study. The mechanical resistance exerted by the testa and endosperm against radicle protrusion in mature caper seeds was measured. The best germination results were obtained with seeds devoid of testa wetted with water and with intact seeds wetted with a 500 mg L-1 GA3 solution, without statistical differences between them. The GA3 addition triggers an increase in both the content of endogenous gibberellins (GA) and the GA/abscisic acid ratio, increasing germination. Its germination consists of two temporally separated events: testa cracking and endosperm piercing. Testa cracking begins in the hilum-micropillar area; it involves a signal from the embryo, which GA can replace, possibly by increasing the growth potential of the embryo. After testa cracking, the radicle emerges through a hole in the micropylar endosperm. The puncture force necessary to pierce the micropylar endosperm decreased drastically during the first day of imbibition, remaining practically constant until testa cracking, decreasing afterwards, regardless of the addition or not of gibberellins.

The Imbibition, Viability, and Germination of Caper Seeds (Capparisspinosa L.) in the First Year of Storage.

The caper is a shrub that adapts to harsh environments when it is established, but it presents serious difficulties in its propagation, both by cuttings and by seeds. Its seeds have low germination percentages, and germination is a very slow process. Significant increases in germination have been obtained with scarification and with the addition of gibberellic acid (GA3) to the substrate, leading to the hypothesis that they have possible physical and physiological dormancy. However, the only way to examine the water-impermeability of the cover is through imbibition analysis. This study analyzes the imbibition, viability, and germination of two seed lots, obtained in different years and evaluated immediately after their collection (FS) and after being stored (7 °C) for one month (DS) and one year (SS). The seed moisture content stabilizes from the fourth day, exceeding in all cases 31% in all three seed states tested (FS, DS and SS). This allows the germination of all viable seeds, only with the addition of GA3 to the germination substrate, without the need for scarification, so that caper seeds exclusively appear to present a physiological latency. Germination decreased in storage, even with just one month. With the GA3 addition, high germination values were obtained (up to 95% in FS).

Determination of crop coefficient for chufa crop (Cyperus esculentus L. var. sativus Boeck.) for sustainable irrigation scheduling.

Chufa is a traditional crop in L'Horta de València (Spain), a historical agricultural system that has been recognised in the register of Globally Important Agricultural Heritage Systems, managed by the Food and Agriculture Organization of the United Nations (FAO), and is one of the six protected Mediterranean and metropolitan horticultural fields as per the European Environment Agency. Chufa is a horticultural crop cultivated for its tubers. Our team has carried out different studies to improve the sustainability of chufa crop, particularly the efficiency of irrigation water use; however, the complete irrigation water requirements remain unknown. Therefore, the main aim of this study was to determine the crop coefficient values for chufa crop along its crop cycle using a smart field weighing lysimeter for three consecutive seasons and to determine its irrigation water requirements. The single crop coefficient values are 0.32, 1.40, and 0.80 for the initial stage, mid-season stage, and end of the late season stage, respectively for local conditions and 1.24 and 0.73 for mid- and late season stages, respectively for standard conditions. FAO segmented and second-order polynomial functions are presented to describe the crop coefficient evolution throughout the cycle, and could be used for irrigation scheduling and may lead to important water savings. The average seasonal net irrigation water requirement for chufa crop was approximately 640 mm, representing around 57% of the irrigation depth usually applied by chufa growers. The water savings that may be achieved by the adjustment of irrigation water with irrigation water requirements, using the crop coefficient, would improve, to a great extent, the sustainability of the L'Horta de València historical agricultural system, in view of the water scarcity resulting from climate change. This sustainable irrigation scheduling will improve the ecosystem indices, which have been altered by the application of over-irrigation, in the area.