Crop yield response to water - Cra
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Crop yield response to water - Cra

Crop yield response to water - Cra Crop yield response to water - Cra

sito.entecra.it
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10.07.2015 Views

Description of the stages of developmentin relation to yield determinationThe reproductive growth of pistachio trees can be divided into three stages based upon thedevelopment of the nut component parts: the hull+shell and the kernel. The developmentpatterns of the nut components are shown in Figure 2. The hull+shell grows rapidly from lateApril through mid-May (Northern Hemisphere), after which full size is attained. This periodis referred to as Stage I. However, the feniculous (embryo), which will eventually evolve intothe kernel, normally does not begin to grow until early July. From mid-May through earlyJuly, the nut's primary growth activity is thickening of the shell. This period, characterizedby a relatively low rate of dry matter accumulation in the nut, is known as Stage II. Rapidgrowth of the kernel begins in early July and remains so as harvest is approached. The biofixfor this period, which is known as Stage III, is the appearance of a distinct green colour in thefeniculous. Research (Spann et al., 2009) has identified the concomitant vegetative growthassociated with these stages and their eventual importance as locations for fruiting positions.Early vegetative and reproductive growth; growth Stage 1Shoot growth occurs simultaneously with the current season reproductive growth (swellingbuds that will form the crop) as well as with embryonic (inflorescence primordia) buddevelopment for the following season’s crop from late April through mid May. Lateralinflorescences in the leaf axils are borne on shoots with, generally, a single apical vegetativebud. Buds differentiate in April, May and June, remain quiescent from July to September,and resume differentiation in October.Figure 2Time course development of dry matter accumulation in pistachio nuts illustrating the threegrowth stages. Vertical bars are plus and minus one standard error of the mean.Fruit dry matter accumulation rate (g/day)0.0200.0180.0160.0140.0120.0100.0080.0060.0040.002Stage IStage IIStage III0.000Apr. 16May 1May 16May 31June 15June 30July 15July 30Aug. 14Aug. 29418crop yield response to water

There are two types of shoot growth; the above-mentioned preformed or neoformed.All components of a preformed shoot are differentiated in the dormant bud whereas inneoformed growth, some differentiation of its component parts can occur during the growingseason. Most of the buds found on preformed growth are reproductive; there are very fewlateral vegetative buds on preformed shoots. Most of the vegetative growth occurs fromterminal buds. Preformed shoots tend to be short compared with neoformed shoots whichare longer. This longer shoot growth is undesirable because it tends to be weak and hangsdown in the orchard rows, making management and harvest difficult. For these reasons,growers typically remove these shoots on mature trees by pruning during the dormant season.However, long shoot growth may be desirable in young, developing trees to ensure the mostrapid development of the tree canopy.Reproductive bud swelling begins in March. By mid-April, there are 100-300 flowers per rachis.Pollination and fruit set occur at this time. There are generally 20-25 developing fruit perrachis and they grow rapidly, with the hull+shell attaining full size by about mid-May. Thisevent also coincides with a hardening of the shell.Lag phase of reproductive growth: growth Stage IIFrom mid-May through early July, the primary activity in the nut is thickening and hardeningof the shells, a process called lignification. However, dry matter accumulation in the fruitduring this growth phase is low relative to the preceding (Stage I) and succeeding (Stage III)periods. There may also be some additional shoot growth in late May. Reproductive buds thatwill form the following season’s fruit continue to differentiate through June. Sometimes thereis an additional vegetative flush of growth in late June.Rapid kernel development: growth Stage IIIThis phase is characterized by the resumption of a high rate of dry matter accumulationin the nut almost entirely results from the rapid growth of the kernel. Within a matterof a few weeks, the kernel will entirely fill the nut cavity and begin to exert pressure onthe shell. Shell splitting is primarily because of this expansion of the kernel (Polito andPinney, 1999). Shell splitting generally begins in early August. At this time, the hull beginsto breakdown, changing from turgid tissue that is tightly bound to the shell with a papery,loosely connected covering that can easily be peeled from the shell. During Stage III, leaveson the same shoot as developing fruit sometimes become yellow and defoliate. This isthought to be the consequence of translocation of resources from the leaves to the fruit.A certain percentage of the nuts, generally from 10 to 30 percent, do not fill. These are knownas ‘blanks’ or ‘aborted’ nuts. With the former, there is no evidence of any development of theembryo whereas with the latter, the embryo development is aborted. The term ‘blanking’is sometimes used to describe both phenomena. The hulls of these nuts do not breakdownas with the filled nuts. Also they are much more difficult to remove from the tree withmechanical shaking at harvest, resulting in a high percentage remaining on the tree.Harvest is generally from late August to mid-September. Where it is done mechanically byshaking machines, similar to those used for almonds, which remove the nuts. In addition to theshaker, a companion machine, the receiver, is located on the opposite side of the tree and isPISTACHIO 419

Description of the stages of developmentin relation <strong>to</strong> <strong>yield</strong> determinationThe reproductive growth of pistachio trees can be divided in<strong>to</strong> three stages based upon thedevelopment of the nut component parts: the hull+shell and the kernel. The developmentpatterns of the nut components are shown in Figure 2. The hull+shell grows rapidly from lateApril through mid-May (Northern Hemisphere), after which full size is attained. This periodis referred <strong>to</strong> as Stage I. However, the feniculous (embryo), which will eventually evolve in<strong>to</strong>the kernel, normally does not begin <strong>to</strong> grow until early July. From mid-May through earlyJuly, the nut's primary growth activity is thickening of the shell. This period, characterizedby a relatively low rate of dry matter accumulation in the nut, is known as Stage II. Rapidgrowth of the kernel begins in early July and remains so as harvest is approached. The biofixfor this period, which is known as Stage III, is the appearance of a distinct green colour in thefeniculous. Research (Spann et al., 2009) has identified the concomitant vegetative growthassociated with these stages and their eventual importance as locations for fruiting positions.Early vegetative and reproductive growth; growth Stage 1Shoot growth occurs simultaneously with the current season reproductive growth (swellingbuds that will form the crop) as well as with embryonic (inflorescence primordia) buddevelopment for the following season’s crop from late April through mid May. Lateralinflorescences in the leaf axils are borne on shoots with, generally, a single apical vegetativebud. Buds differentiate in April, May and June, remain quiescent from July <strong>to</strong> September,and resume differentiation in Oc<strong>to</strong>ber.Figure 2Time course development of dry matter accumulation in pistachio nuts illustrating the threegrowth stages. Vertical bars are plus and minus one standard error of the mean.Fruit dry matter accumulation rate (g/day)0.0200.0180.0160.0140.0120.0100.0080.0060.0040.002Stage IStage IIStage III0.000Apr. 16May 1May 16May 31June 15June 30July 15July 30Aug. 14Aug. 29418crop <strong>yield</strong> <strong>response</strong> <strong>to</strong> <strong>water</strong>

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